FreeBSD Manual Pages
QEMU(1) QEMU QEMU(1) NAME qemu - QEMU User Documentation SYNOPSIS qemu-system-x86_64 [options] [disk_image] DESCRIPTION The QEMU PC System emulator simulates the following peripherals: * i440FX host PCI bridge and PIIX3 PCI to ISA bridge * Cirrus CLGD 5446 PCI VGA card or dummy VGA card with Bochs VESA exten- sions (hardware level, including all non standard modes). * PS/2 mouse and keyboard * 2 PCI IDE interfaces with hard disk and CD-ROM support * Floppy disk * PCI and ISA network adapters * Serial ports * IPMI BMC, either and internal or external one * Creative SoundBlaster 16 sound card * ENSONIQ AudioPCI ES1370 sound card * Intel 82801AA AC97 Audio compatible sound card * Intel HD Audio Controller and HDA codec * Adlib (OPL2) - Yamaha YM3812 compatible chip * Gravis Ultrasound GF1 sound card * CS4231A compatible sound card * PC speaker * PCI UHCI, OHCI, EHCI or XHCI USB controller and a virtual USB-1.1 hub. SMP is supported with a large number of virtual CPUs (upper limit is con- figuration dependent). QEMU uses the PC BIOS from the Seabios project and the Plex86/Bochs LGPL VGA BIOS. QEMU uses YM3812 emulation by Tatsuyuki Satoh. QEMU uses GUS emulation (GUSEMU32 http://www.deinmeister.de/gusemu/) by Ti- bor "TS" SchA1/4tz. Note that, by default, GUS shares IRQ(7) with parallel ports and so QEMU must be told to not have parallel ports to have working GUS. qemu-system-x86_64 dos.img -device gus -parallel none Alternatively: qemu-system-x86_64 dos.img -device gus,irq=5 Or some other unclaimed IRQ. CS4231A is the chip used in Windows Sound System and GUSMAX products The PC speaker audio device can be configured using the pcspk-audiodev ma- chine property, i.e. qemu-system-x86_64 some.img -audiodev <backend>,id=<name> -machine pcspk-audiodev=<name> Machine-specific options It supports the following machine-specific options: * x-south-bridge=PIIX3|piix4-isa (Experimental option to select a particu- lar south bridge. Default: PIIX3) OPTIONS disk_image is a raw hard disk image for IDE hard disk 0. Some targets do not need a disk image. When dealing with options parameters as arbitrary strings containing com- mas, such as in "file=my,file" and "string=a,b", it's necessary to double the commas. For instance,"-fw_cfg name=z,string=a,,b" will be parsed as "-fw_cfg name=z,string=a,b". Standard options -h Display help and exit -version Display version information and exit -machine [type=]name[,prop=value[,...]] Select the emulated machine by name. Use -machine help to list available machines. For architectures which aim to support live migration compatibility across releases, each release will introduce a new versioned machine type. For example, the 2.8.0 release introduced machine types "pc-i440fx-2.8" and "pc-q35-2.8" for the x86_64/i686 architectures. To allow live migration of guests from QEMU version 2.8.0, to QEMU version 2.9.0, the 2.9.0 version must support the "pc-i440fx-2.8" and "pc-q35-2.8" machines too. To allow users live migrating VMs to skip multiple intermediate releases when upgrading, new releases of QEMU will support machine types from many previous versions. Supported machine properties are: accel=accels1[:accels2[:...]] This is used to enable an accelerator. Depending on the tar- get architecture, kvm, xen, hvf, nitro, nvmm, whpx, mshv or tcg can be available. By default, tcg is used. If there is more than one accelerator specified, the next one is used if the previous one fails to initialize. vmport=on|off|auto Enables emulation of VMWare IO port, for vmmouse etc. auto says to select the value based on accel and i8042. For ac- cel=xen or i8042=off the default is off otherwise the default is on. dump-guest-core=on|off Include guest memory in a core dump. The default is on. mem-merge=on|off Enables or disables memory merge support. This feature, when supported by the host, de-duplicates identical memory pages among VMs instances (enabled by default). aes-key-wrap=on|off Enables or disables AES key wrapping support on s390-ccw hosts. This feature controls whether AES wrapping keys will be created to allow execution of AES cryptographic functions. The default is on. dea-key-wrap=on|off Enables or disables DEA key wrapping support on s390-ccw hosts. This feature controls whether DEA wrapping keys will be created to allow execution of DEA cryptographic functions. The default is on. nvdimm=on|off Enables or disables NVDIMM support. The default is off. memory-encryption=<id> Memory encryption object to use. The default is none. hmat=on|off Enables or disables ACPI Heterogeneous Memory Attribute Table (HMAT) support. The default is off. spcr=on|off Enables or disables ACPI Serial Port Console Redirection Ta- ble (SPCR) support. The default is on. aux-ram-share=on|off Allocate auxiliary guest RAM as an anonymous file that is shareable with an external process. This option applies to memory allocated as a side effect of creating various de- vices. It does not apply to memory-backend-objects, whether explicitly specified on the command line, or implicitly cre- ated by the -m command line option. The default is off. To use the cpr-transfer migration mode, you must set aux-ram-share=on. memory-backend='id' An alternative to legacy -mem-path and mem-prealloc options. Allows to use a memory backend as main RAM. For example: -object memory-backend-file,id=pc.ram,size=512M,mem-path=/hugetlbfs,prealloc=on,share=on -machine memory-backend=pc.ram -m 512M Migration compatibility note: * as backend id one shall use value of 'default-ram-id', ad- vertised by machine type (available via query-machines QMP command), if migration to/from old QEMU (<5.0) is expected. * for machine types 4.0 and older, user shall use x-use-canonical-path-for-ramblock-id=off backend option if migration to/from old QEMU (<5.0) is expected. For example: -object memory-backend-ram,id=pc.ram,size=512M,x-use-canonical-path-for-ramblock-id=off -machine memory-backend=pc.ram -m 512M cxl-fmw.0.targets.0=firsttarget,cxl-fmw.0.targets.1=secondtar- get,cxl-fmw.0.size=size[,cxl-fmw.0.interleave-granularity=granular- ity] Define a CXL Fixed Memory Window (CFMW). Described in the CXL 2.0 ECN: CEDT CFMWS & QTG _DSM. They are regions of Host Physical Addresses (HPA) on a system which may be interleaved across one or more CXL host bridges. The system software will assign particular devices into these windows and configure the downstream Host-managed Device Mem- ory (HDM) decoders in root ports, switch ports and devices appropriately to meet the interleave requirements before en- abling the memory devices. targets.X=target provides the mapping to CXL host bridges which may be identified by the id provided in the -device en- try. Multiple entries are needed to specify all the targets when the fixed memory window represents interleaved memory. X is the target index from 0. size=size sets the size of the CFMW. This must be a multiple of 256MiB. The region will be aligned to 256MiB but the loca- tion is platform and configuration dependent. interleave-granularity=granularity sets the granularity of interleave. Default 256 (bytes). Only 256, 512, 1k, 2k, 4k, 8k and 16k granularities supported. Example: -machine cxl-fmw.0.targets.0=cxl.0,cxl-fmw.0.targets.1=cxl.1,cxl-fmw.0.size=128G,cxl-fmw.0.interleave-granularity=512 sgx-epc.0.memdev=<memid>,sgx-epc.0.node=<numaid> Define an SGX EPC section. smp-cache.0.cache=cachename,smp-cache.0.topology=topologylevel Define cache properties for SMP system. cache=cachename specifies the cache that the properties will be applied on. This field is the combination of cache level and cache type. It supports l1d (L1 data cache), l1i (L1 in- struction cache), l2 (L2 unified cache) and l3 (L3 unified cache). topology=topologylevel sets the cache topology level. It ac- cepts CPU topology levels including core, module, cluster, die, socket, book, drawer and a special value default. If de- fault is set, then the cache topology will follow the archi- tecture's default cache topology model. If another topology level is set, the cache will be shared at corresponding CPU topology level. For example, topology=core makes the cache shared by all threads within a core. The omitting cache will default to using the default level. The default cache topology model for an i386 PC machine is as follows: l1d, l1i, and l2 caches are per core, while the l3 cache is per die. Example: -machine smp-cache.0.cache=l1d,smp-cache.0.topology=core,smp-cache.1.cache=l1i,smp-cache.1.topology=core -M as -machine. -cpu model Select CPU model (-cpu help for list and additional feature selec- tion) -accel name[,prop=value[,...]] This is used to enable an accelerator. Depending on the target ar- chitecture, kvm, xen, hvf, nitro, nvmm, whpx, mshv or tcg can be available. By default, tcg is used. If there is more than one ac- celerator specified, the next one is used if the previous one fails to initialize. igd-passthru=on|off When Xen is in use, this option controls whether Intel inte- grated graphics devices can be passed through to the guest (default=off) kernel-irqchip=on|off|split Controls KVM in-kernel irqchip support. The default is full acceleration of the interrupt controllers. On x86, split irqchip reduces the kernel attack surface, at a performance cost for non-MSI interrupts. Disabling the in-kernel irqchip completely is not recommended except for debugging purposes. kvm-shadow-mem=size Defines the size of the KVM shadow MMU. one-insn-per-tb=on|off Makes the TCG accelerator put only one guest instruction into each translation block. This slows down emulation a lot, but can be useful in some situations, such as when trying to analyse the logs produced by the -d option. split-wx=on|off Controls the use of split w^x mapping for the TCG code gener- ation buffer. Some operating systems require this to be en- abled, and in such a case this will default on. On other op- erating systems, this will default off, but one may enable this for testing or debugging. tb-size=n Controls the size (in MiB) of the TCG translation block cache. thread=single|multi Controls number of TCG threads. When the TCG is multi-threaded there will be one thread per vCPU therefore taking advantage of additional host cores. The default is to enable multi-threading where both the back-end and front-ends support it and no incompatible TCG features have been enabled (e.g. icount/replay). dirty-ring-size=n When the KVM accelerator is used, it controls the size of the per-vCPU dirty page ring buffer (number of entries for each vCPU). It should be a value that is power of two, and it should be 1024 or bigger (but still less than the maximum value that the kernel supports). 4096 could be a good ini- tial value if you have no idea which is the best. Set this value to 0 to disable the feature. By default, this feature is disabled (dirty-ring-size=0). When enabled, KVM will in- stead record dirty pages in a bitmap. eager-split-size=n KVM implements dirty page logging at the PAGE_SIZE granular- ity and enabling dirty-logging on a huge-page requires break- ing it into PAGE_SIZE pages in the first place. KVM on ARM does this splitting lazily by default. There are performance benefits in doing huge-page split eagerly, especially in sit- uations where TLBI costs associated with break-before-make sequences are considerable and also if guest workloads are read intensive. The size here specifies how many pages to break at a time and needs to be a valid block size which is 1GiB/2MiB/4KiB, 32MiB/16KiB and 512MiB/64KiB for 4KiB/16KiB/64KiB PAGE_SIZE respectively. Be wary of specify- ing a higher size as it will have an impact on the memory. By default, this feature is disabled (eager-split-size=0). notify-vmexit=run|internal-error|disable,notify-window=n Enables or disables notify VM exit support on x86 host and specify the corresponding notify window to trigger the VM exit if enabled. run option enables the feature. It does nothing and continue if the exit happens. internal-error op- tion enables the feature. It raises a internal error. dis- able option doesn't enable the feature. This feature can mitigate the CPU stuck issue due to event windows don't open up for a specified of time (i.e. notify-window). Default: notify-vmexit=run,notify-window=0. device=path Sets the path to the KVM device node. Defaults to /dev/kvm. This option can be used to pass the KVM device to use via a file descriptor by setting the value to /dev/fdset/NN. hyperv=on|off|auto For the WHPX backend, determines whether to enable Hyper-V enlightenments. On x86_64, Hyper-V enlightenments are on by default. On AArch64, they're off by default. -smp [[cpus=]n][,maxcpus=maxcpus][,drawers=drawers][,books=books][,sock- ets=sockets][,dies=dies][,clusters=clusters][,modules=mod- ules][,cores=cores][,threads=threads] Simulate a SMP system with 'n' CPUs initially present on the machine type board. On boards supporting CPU hotplug, the optional 'maxcpus' parameter can be set to enable further CPUs to be added at runtime. When both parameters are omitted, the maximum number of CPUs will be calculated from the provided topology members and the initial CPU count will match the maximum number. When only one of them is given then the omitted one will be set to its counterpart's value. Both parameters may be specified, but the maximum number of CPUs must be equal to or greater than the initial CPU count. Product of the CPU topology hierarchy must be equal to the maximum number of CPUs. Both parameters are subject to an upper limit that is determined by the specific machine type chosen. To control reporting of CPU topology information, values of the topology parameters can be specified. Machines may only support a subset of the parameters and different machines may have different subsets supported which vary depending on capacity of the corre- sponding CPU targets. So for a particular machine type board, an ex- pected topology hierarchy can be defined through the supported sub-option. Unsupported parameters can also be provided in addition to the sub-option, but their values must be set as 1 in the purpose of correct parsing. Either the initial CPU count, or at least one of the topology para- meters must be specified. The specified parameters must be greater than zero, explicit configuration like "cpus=0" is not allowed. Val- ues for any omitted parameters will be computed from those which are given. For example, the following sub-option defines a CPU topology hierar- chy (2 sockets totally on the machine, 2 cores per socket, 2 threads per core) for a machine that only supports sockets/cores/threads. Some members of the option can be omitted but their values will be automatically computed: -smp 8,sockets=2,cores=2,threads=2,maxcpus=8 The following sub-option defines a CPU topology hierarchy (2 sockets totally on the machine, 2 dies per socket, 2 modules per die, 2 cores per module, 2 threads per core) for PC machines which support sockets/dies /modules/cores/threads. Some members of the option can be omitted but their values will be automatically computed: -smp 32,sockets=2,dies=2,modules=2,cores=2,threads=2,maxcpus=32 The following sub-option defines a CPU topology hierarchy (2 sockets totally on the machine, 2 clusters per socket, 2 cores per cluster, 2 threads per core) for ARM virt machines which support sock- ets/clusters /cores/threads. Some members of the option can be omit- ted but their values will be automatically computed: -smp 16,sockets=2,clusters=2,cores=2,threads=2,maxcpus=16 Historically preference was given to the coarsest topology parame- ters when computing missing values (ie sockets preferred over cores, which were preferred over threads), however, this behaviour is con- sidered liable to change. Prior to 6.2 the preference was sockets over cores over threads. Since 6.2 the preference is cores over sockets over threads. For example, the following option defines a machine board with 2 sockets of 1 core before 6.2 and 1 socket of 2 cores after 6.2: -smp 2 Note: The cluster topology will only be generated in ACPI and ex- posed to guest if it's explicitly specified in -smp. -numa node[,mem=size][,cpus=firstcpu[-lastcpu]][,nodeid=node][,initia- tor=initiator] -numa node[,memdev=id][,cpus=firstcpu[-lastcpu]][,nodeid=node][,initia- tor=initiator] -numa dist,src=source,dst=destination,val=distance -numa cpu,node-id=node[,socket-id=x][,core-id=y][,thread-id=z] -numa hmat-lb,initiator=node,target=node,hierarchy=hierar- chy,data-type=type[,latency=lat][,bandwidth=bw] -numa hmat-cache,node-id=node,size=size,level=level[,associativ- ity=str][,policy=str][,line=size] Define a NUMA node and assign RAM and VCPUs to it. Set the NUMA dis- tance from a source node to a destination node. Set the ACPI Hetero- geneous Memory Attributes for the given nodes. Legacy VCPU assignment uses 'cpus' option where firstcpu and lastcpu are CPU indexes. Each 'cpus' option represent a contiguous range of CPU indexes (or a single VCPU if lastcpu is omitted). A non-contigu- ous set of VCPUs can be represented by providing multiple 'cpus' op- tions. If 'cpus' is omitted on all nodes, VCPUs are automatically split between them. For example, the following option assigns VCPUs 0, 1, 2 and 5 to a NUMA node: -numa node,cpus=0-2,cpus=5 'cpu' option is a new alternative to 'cpus' option which uses 'socket-id|core-id|thread-id' properties to assign CPU objects to a node using topology layout properties of CPU. The set of properties is machine specific, and depends on used machine type/'smp' options. It could be queried with 'hotpluggable-cpus' monitor command. 'node-id' property specifies node to which CPU object will be as- signed, it's required for node to be declared with 'node' option be- fore it's used with 'cpu' option. For example: -M pc \ -smp 1,sockets=2,maxcpus=2 \ -numa node,nodeid=0 -numa node,nodeid=1 \ -numa cpu,node-id=0,socket-id=0 -numa cpu,node-id=1,socket-id=1 'memdev' option assigns RAM from a given memory backend device to a node. It is recommended to use 'memdev' option over legacy 'mem' op- tion. This is because 'memdev' option provides better performance and more control over the backend's RAM (e.g. 'prealloc' parameter of '-memory-backend-ram' allows memory preallocation). For compatibility reasons, legacy 'mem' option is supported in 5.0 and older machine types. Note that 'mem' and 'memdev' are mutually exclusive. If one node uses 'memdev', the rest nodes have to use 'memdev' option, and vice versa. Users must specify memory for all NUMA nodes by 'memdev' (or legacy 'mem' if available). In QEMU 5.2, the support for '-numa node' with- out memory specified was removed. 'initiator' is an additional option that points to an initiator NUMA node that has best performance (the lowest latency or largest band- width) to this NUMA node. Note that this option can be set only when the machine property 'hmat' is set to 'on'. Following example creates a machine with 2 NUMA nodes, node 0 has CPU. node 1 has only memory, and its initiator is node 0. Note that because node 0 has CPU, by default the initiator of node 0 is itself and must be itself. -machine hmat=on \ -m 2G,slots=2,maxmem=4G \ -object memory-backend-ram,size=1G,id=m0 \ -object memory-backend-ram,size=1G,id=m1 \ -numa node,nodeid=0,memdev=m0 \ -numa node,nodeid=1,memdev=m1,initiator=0 \ -smp 2,sockets=2,maxcpus=2 \ -numa cpu,node-id=0,socket-id=0 \ -numa cpu,node-id=0,socket-id=1 source and destination are NUMA node IDs. distance is the NUMA dis- tance from source to destination. The distance from a node to itself is always 10. If any pair of nodes is given a distance, then all pairs must be given distances. Although, when distances are only given in one direction for each pair of nodes, then the distances in the opposite directions are assumed to be the same. If, however, an asymmetrical pair of distances is given for even one node pair, then all node pairs must be provided distance values for both directions, even when they are symmetrical. When a node is unreachable from an- other node, set the pair's distance to 255. Note that the -numa option doesn't allocate any of the specified re- sources, it just assigns existing resources to NUMA nodes. This means that one still has to use the -m, -smp options to allocate RAM and VCPUs respectively. Use 'hmat-lb' to set System Locality Latency and Bandwidth Informa- tion between initiator and target NUMA nodes in ACPI Heterogeneous Attribute Memory Table (HMAT). Initiator NUMA node can create memory requests, usually it has one or more processors. Target NUMA node contains addressable memory. In 'hmat-lb' option, node are NUMA node IDs. hierarchy is the memory hierarchy of the target NUMA node: if hierarchy is 'memory', the structure represents the memory performance; if hierarchy is 'first-level|second-level|third-level', this structure represents aggregated performance of memory side caches for each domain. type of 'data-type' is type of data represented by this structure in- stance: if 'hierarchy' is 'memory', 'data-type' is 'ac- cess|read|write' latency or 'access|read|write' bandwidth of the target memory; if 'hierarchy' is 'first-level|sec- ond-level|third-level', 'data-type' is 'access|read|write' hit la- tency or 'access|read|write' hit bandwidth of the target memory side cache. lat is latency value in nanoseconds. bw is bandwidth value, the pos- sible value and units are NUM[M|G|T], mean that the bandwidth value are NUM byte per second (or MiB/s, GiB/s or TiB/s depending on used suffix). Note that if latency or bandwidth value is 0, means the corresponding latency or bandwidth information is not provided. In 'hmat-cache' option, node-id is the NUMA-id of the memory be- longs. size is the size of memory side cache in bytes. level is the cache level described in this structure, note that the cache level 0 should not be used with 'hmat-cache' option. associativity is the cache associativity, the possible value is 'none/direct(di- rect-mapped)/complex(complex cache indexing)'. policy is the write policy. line is the cache Line size in bytes. For example, the following options describe 2 NUMA nodes. Node 0 has 2 cpus and a ram, node 1 has only a ram. The processors in node 0 access memory in node 0 with access-latency 5 nanoseconds, ac- cess-bandwidth is 200 MiB/s; The processors in NUMA node 0 access memory in NUMA node 1 with access-latency 10 nanoseconds, ac- cess-bandwidth is 100 MiB/s. And for memory side cache information, NUMA node 0 and 1 both have 1 level memory cache, size is 10KiB, policy is write-back, the cache Line size is 8 bytes: -machine hmat=on \ -m 2G \ -object memory-backend-ram,size=1G,id=m0 \ -object memory-backend-ram,size=1G,id=m1 \ -smp 2,sockets=2,maxcpus=2 \ -numa node,nodeid=0,memdev=m0 \ -numa node,nodeid=1,memdev=m1,initiator=0 \ -numa cpu,node-id=0,socket-id=0 \ -numa cpu,node-id=0,socket-id=1 \ -numa hmat-lb,initiator=0,target=0,hierarchy=memory,data-type=access-latency,latency=5 \ -numa hmat-lb,initiator=0,target=0,hierarchy=memory,data-type=access-bandwidth,bandwidth=200M \ -numa hmat-lb,initiator=0,target=1,hierarchy=memory,data-type=access-latency,latency=10 \ -numa hmat-lb,initiator=0,target=1,hierarchy=memory,data-type=access-bandwidth,bandwidth=100M \ -numa hmat-cache,node-id=0,size=10K,level=1,associativity=direct,policy=write-back,line=8 \ -numa hmat-cache,node-id=1,size=10K,level=1,associativity=direct,policy=write-back,line=8 -add-fd fd=fd,set=set[,opaque=opaque] Add a file descriptor to an fd set. Valid options are: fd=fd This option defines the file descriptor of which a duplicate is added to fd set. The file descriptor cannot be stdin, std- out, or stderr. set=set This option defines the ID of the fd set to add the file de- scriptor to. opaque=opaque This option defines a free-form string that can be used to describe fd. You can open an image using pre-opened file descriptors from an fd set: qemu-system-x86_64 \ -add-fd fd=3,set=2,opaque="rdwr:/path/to/file" \ -add-fd fd=4,set=2,opaque="rdonly:/path/to/file" \ -drive file=/dev/fdset/2,index=0,media=disk -set group.id.arg=value Set parameter arg for item id of type group -global driver.prop=value -global driver=driver,property=property,value=value Set default value of driver's property prop to value, e.g.: qemu-system-x86_64 -global ide-hd.physical_block_size=4096 disk-image.img In particular, you can use this to set driver properties for devices which are created automatically by the machine model. To create a device which is not created automatically and set properties on it, use -device. -global driver.prop=value is shorthand for -global driver=dri- ver,property=prop,value=value. The longhand syntax works even when driver contains a dot. -boot [order=drives][,once=dri- ves][,menu=on|off][,splash=sp_name][,splash-time=sp_time][,reboot-time- out=rb_timeout][,strict=on|off] Specify boot order drives as a string of drive letters. Valid drive letters depend on the target architecture. The x86 PC uses: a, b (floppy 1 and 2), c (first hard disk), d (first CD-ROM), n-p (Ether- boot from network adapter 1-4), hard disk boot is the default. To apply a particular boot order only on the first startup, specify it via once. Note that the order or once parameter should not be used together with the bootindex property of devices, since the firmware implementations normally do not support both at the same time. Interactive boot menus/prompts can be enabled via menu=on as far as firmware/BIOS supports them. The default is non-interactive boot. A splash picture could be passed to bios, enabling user to show it as logo, when option splash=sp_name is given and menu=on, If firmware/BIOS supports them. Currently Seabios for X86 system sup- port it. limitation: The splash file could be a jpeg file or a BMP file in 24 BPP format(true color). The resolution should be sup- ported by the SVGA mode, so the recommended is 320x240, 640x480, 800x640. A timeout could be passed to bios, guest will pause for rb_timeout ms when boot failed, then reboot. If rb_timeout is '-1', guest will not reboot, qemu passes '-1' to bios by default. Currently Seabios for X86 system support it. Do strict boot via strict=on as far as firmware/BIOS supports it. This only effects when boot priority is changed by bootindex op- tions. The default is non-strict boot. # try to boot from network first, then from hard disk qemu-system-x86_64 -boot order=nc # boot from CD-ROM first, switch back to default order after reboot qemu-system-x86_64 -boot once=d # boot with a splash picture for 5 seconds. qemu-system-x86_64 -boot menu=on,splash=/root/boot.bmp,splash-time=5000 Note: The legacy format '-boot drives' is still supported but its use is discouraged as it may be removed from future versions. -m [size=]megs[,slots=n,maxmem=size] Sets guest startup RAM size to megs megabytes. Default is 128 MiB. Optionally, a suffix of "M" or "G" can be used to signify a value in megabytes or gigabytes respectively. Optional pair slots, maxmem could be used to set amount of hotpluggable memory slots and maximum amount of memory. Note that maxmem must be aligned to the page size. For example, the following command-line sets the guest startup RAM size to 1GiB, creates 3 slots to hotplug additional memory and sets the maximum memory the guest can reach to 4GiB: qemu-system-x86_64 -m 1G,slots=3,maxmem=4G If slots and maxmem are not specified, memory hotplug won't be en- abled and the guest startup RAM will never increase. -mem-path path Allocate guest RAM from a temporarily created file in path. -mem-prealloc Preallocate memory when using -mem-path. -k language Use keyboard layout language (for example fr for French). This op- tion is only needed where it is not easy to get raw PC keycodes (e.g. on Macs, with some X11 servers or with a VNC or curses dis- play). You don't normally need to use it on PC/Linux or PC/Windows hosts. The available layouts are: ar de-ch es fo fr-ca hu ja mk no pt-br sv da en-gb et fr fr-ch is lt nl pl ru th de en-us fi fr-be hr it lv nl-be pt sl tr The default is en-us. -audio [driver=]driver[,model=value][,prop=value[,...]] If the model option is specified, -audio is a shortcut for configur- ing both the guest audio hardware and the host audio backend in one go. The guest hardware model can be set with model=modelname. Use model=help to list the available device types. The following two example do exactly the same, to show how -audio can be used to shorten the command line length: qemu-system-x86_64 -audiodev pa,id=pa -device sb16,audiodev=pa qemu-system-x86_64 -audio pa,model=sb16 If the model option is not specified, -audio is used to configure a default audio backend that will be used whenever the audiodev prop- erty is not set on a device or machine. In particular, -audio none ensures that no audio is produced even for machines that have embed- ded sound hardware. In both cases, the driver option is the same as with the correspond- ing -audiodev option below. Use driver=help to list the available drivers. -audiodev [driver=]driver,id=id[,prop=value[,...]] Adds a new audio backend driver identified by id. If no audio backend is specified, QEMU will attempt to select a de- fault one. The -display option may influence which backend is se- lected. There are global and driver specific properties. Some values can be set differently for input and output, they're marked with in|out.. You can set the input's property with in.prop and the output's prop- erty with out.prop. For example: -audiodev alsa,id=example,in.frequency=44110,out.frequency=8000 -audiodev alsa,id=example,out.channels=1 # leaves in.channels unspecified NOTE: parameter validation is known to be incomplete, in many cases specifying an invalid option causes QEMU to print an error message and continue emulation without sound. Valid global options are: id=identifier Identifies the audio backend. timer-period=period Sets the timer period used by the audio subsystem in mi- croseconds. Default is 10000 (10 ms). in|out.mixing-engine=on|off Use QEMU's mixing engine to mix all streams inside QEMU and convert audio formats when not supported by the backend. When off, fixed-settings must be off too. Note that disabling this option means that the selected backend must support multiple streams and the audio formats used by the virtual cards, oth- erwise you'll get no sound. It's not recommended to disable this option unless you want to use 5.1 or 7.1 audio, as mix- ing engine only supports mono and stereo audio. Default is on. in|out.fixed-settings=on|off Use fixed settings for host audio. When off, it will change based on how the guest opens the sound card. In this case you must not specify frequency, channels or format. Default is on. in|out.frequency=frequency Specify the frequency to use when using fixed-settings. De- fault is 44100Hz. in|out.channels=channels Specify the number of channels to use when using fixed-set- tings. Default is 2 (stereo). in|out.format=format Specify the sample format to use when using fixed-settings. Valid values are: s8, s16, s32, u8, u16, u32, f32. Default is s16. in|out.voices=voices Specify the number of voices to use. Default is 1. in|out.buffer-length=usecs Sets the size of the buffer in microseconds. -audiodev none,id=id[,prop=value[,...]] Creates a dummy backend that discards all outputs. This backend has no backend specific properties. -audiodev alsa,id=id[,prop=value[,...]] Creates backend using the ALSA. This backend is only available on Linux. ALSA specific options are: in|out.dev=device Specify the ALSA device to use for input and/or output. De- fault is default. in|out.period-length=usecs Sets the period length in microseconds. in|out.try-poll=on|off Attempt to use poll mode with the device. Default is off. threshold=threshold Threshold (in microseconds) when playback starts. Default is 0. -audiodev coreaudio,id=id[,prop=value[,...]] Creates a backend using Apple's Core Audio. This backend is only available on Mac OS and only supports playback. Core Audio specific options are: in|out.buffer-count=count Sets the count of the buffers. -audiodev dbus,id=id[,prop=value[,...]] Creates a D-Bus backend. It must be associated with the display (as -display dbus,audiodev=id). (Since 7.0) D-Bus specific options are: nsamples Number of samples per read/write (default to 480, 10ms at 48kHz) (Since 10.0) -audiodev dsound,id=id[,prop=value[,...]] Creates a backend using Microsoft's DirectSound. This backend is only available on Windows and only supports playback. DirectSound specific options are: latency=usecs Add extra usecs microseconds latency to playback. Default is 10000 (10 ms). -audiodev oss,id=id[,prop=value[,...]] Creates a backend using OSS. This backend is available on most Unix-like systems. OSS specific options are: in|out.dev=device Specify the file name of the OSS device to use. Default is /dev/dsp. in|out.buffer-count=count Sets the count of the buffers. in|out.try-poll=on|off Attempt to use poll mode with the device. Default is on. try-mmap=on|off Try using memory mapped device access. Default is off. exclusive=on|off Open the device in exclusive mode (vmix won't work in this case). Default is off. dsp-policy=policy Sets the timing policy (between 0 and 10, where smaller num- ber means smaller latency but higher CPU usage). Use -1 to use buffer sizes specified by buffer and buffer-count. This option is ignored if you do not have OSS 4. Default is 5. -audiodev pa,id=id[,prop=value[,...]] Creates a backend using PulseAudio. This backend is available on most systems. PulseAudio specific options are: server=server Sets the PulseAudio server to connect to. in|out.name=sink Use the specified source/sink for recording/playback. in|out.latency=usecs Desired latency in microseconds. The PulseAudio server will try to honor this value but actual latencies may be lower or higher. -audiodev pipewire,id=id[,prop=value[,...]] Creates a backend using PipeWire. This backend is available on most systems. PipeWire specific options are: in|out.latency=usecs Desired latency in microseconds. in|out.name=sink Use the specified source/sink for recording/playback. in|out.stream-name Specify the name of pipewire stream. -audiodev sdl,id=id[,prop=value[,...]] Creates a backend using SDL. This backend is available on most sys- tems, but you should use your platform's native backend if possible. SDL specific options are: in|out.buffer-count=count Sets the count of the buffers. -audiodev sndio,id=id[,prop=value[,...]] Creates a backend using SNDIO. This backend is available on OpenBSD and most other Unix-like systems. Sndio specific options are: in|out.dev=device Specify the sndio device to use for input and/or output. De- fault is default. in|out.latency=usecs Sets the desired period length in microseconds. -audiodev spice,id=id[,prop=value[,...]] Creates a backend that sends audio through SPICE. This backend re- quires -spice and automatically selected in that case, so usually you can ignore this option. This backend has no backend specific properties. -audiodev wav,id=id[,prop=value[,...]] Creates a backend that writes audio to a WAV file. Backend specific options are: path=path Write recorded audio into the specified file. Default is qemu.wav. -device driver[,prop=value[,...]] Add device driver. prop=value sets driver properties. Valid proper- ties depend on the driver. To get help on possible drivers and prop- erties, use -device help and -device driver,help. Some drivers are: -device ipmi-bmc-sim,id=id[,prop=value[,...]] Add an IPMI BMC. This is a simulation of a hardware management in- terface processor that normally sits on a system. It provides a watchdog and the ability to reset and power control the system. You need to connect this to an IPMI interface to make it useful The IPMI slave address to use for the BMC. The default is 0x20. This address is the BMC's address on the I2C network of management con- trollers. If you don't know what this means, it is safe to ignore it. id=id The BMC id for interfaces to use this device. slave_addr=val Define slave address to use for the BMC. The default is 0x20. sdrfile=file file containing raw Sensor Data Records (SDR) data. The de- fault is none. fruareasize=val size of a Field Replaceable Unit (FRU) area. The default is 1024. frudatafile=file file containing raw Field Replaceable Unit (FRU) inventory data. The default is none. guid=uuid value for the GUID for the BMC, in standard UUID format. If this is set, get "Get GUID" command to the BMC will return it. Otherwise "Get GUID" will return an error. lan.channel=val channel number of the fake LAN channel. It can be 0 or any integer from 0x1 to 0xb inclusive. If set to 0, the LAN chan- nel is disabled, otherwise the LAN channel is enabled at the specified channel number. The default is 0. lan.ipaddr=addr the ipv4 address of the BMC LAN channel. lan.ipsrc=val the ipv4 address source of the BMC LAN channel. It can be 0 (unspecified source), 1 (static address), 2 (DHCP), 3 (BIOS or system software), or 4 (other source). The default is 0. lan.macaddr=mac the mac address of the BMC LAN channel. lan.netmask=mask the ipv4 subnet mask for the BMC LAN channel. lan.defgw_ipaddr=addr the default gateway ipv4 address for the BMC LAN channel. lan.defgw_macaddr=mac the default gateway mac address for the BMC LAN channel. -device ipmi-bmc-extern,id=id,chardev=id[,slave_addr=val] Add a connection to an external IPMI BMC simulator. Instead of lo- cally emulating the BMC like the above item, instead connect to an external entity that provides the IPMI services. A connection is made to an external BMC simulator. If you do this, it is strongly recommended that you use the "reconnect-ms=" chardev option to reconnect to the simulator if the connection is lost. Note that if this is not used carefully, it can be a security issue, as the interface has the ability to send resets, NMIs, and power off the VM. It's best if QEMU makes a connection to an external simula- tor running on a secure port on localhost, so neither the simulator nor QEMU is exposed to any outside network. See the "lanserv/README.vm" file in the OpenIPMI library for more details on the external interface. -device isa-ipmi-kcs,bmc=id[,ioport=val][,irq=val] Add a KCS IPMI interface on the ISA bus. This also adds a corre- sponding ACPI and SMBIOS entries, if appropriate. bmc=id The BMC to connect to, one of ipmi-bmc-sim or ipmi-bmc-extern above. ioport=val Define the I/O address of the interface. The default is 0xca0 for KCS. irq=val Define the interrupt to use. The default is 5. To disable in- terrupts, set this to 0. -device isa-ipmi-bt,bmc=id[,ioport=val][,irq=val] Like the KCS interface, but defines a BT interface. The default port is 0xe4 and the default interrupt is 5. -device pci-ipmi-kcs,bmc=id Add a KCS IPMI interface on the PCI bus. bmc=id The BMC to connect to, one of ipmi-bmc-sim or ipmi-bmc-extern above. -device pci-ipmi-bt,bmc=id Like the KCS interface, but defines a BT interface on the PCI bus. -device intel-iommu[,option=...] This is only supported by -machine q35, which will enable Intel VT-d emulation within the guest. It supports below options: intremap=on|off (default: auto) This enables interrupt remapping feature. It's required to enable complete x2apic. Currently it only supports kvm ker- nel-irqchip modes off or split, while full kernel-irqchip is not yet supported. The default value is "auto", which will be decided by the mode of kernel-irqchip. caching-mode=on|off (default: off) This enables caching mode for the VT-d emulated device. When caching-mode is enabled, each guest DMA buffer mapping will generate an IOTLB invalidation from the guest IOMMU driver to the vIOMMU device in a synchronous way. It is required for -device vfio-pci to work with the VT-d device, because host assigned devices requires to setup the DMA mapping on the host before guest DMA starts. device-iotlb=on|off (default: off) This enables device-iotlb capability for the emulated VT-d device. So far virtio/vhost should be the only real user for this parameter, paired with ats=on configured for the device. aw-bits=39|48 (default: 39) This decides the address width of IOVA address space. The address space has 39 bits width for 3-level IOMMU page ta- bles, and 48 bits for 4-level IOMMU page tables. Please also refer to the wiki page for general scenarios of VT-d em- ulation in QEMU: https://wiki.qemu.org/Features/VT-d. -device virtio-iommu-pci[,option=...] This is only supported by -machine q35 (x86_64) and -machine virt (ARM). It supports below options: granule=val (possible values are 4k, 8k, 16k, 64k and host; default: host) This decides the default granule to be be exposed by the vir- tio-iommu. If host, the granule matches the host page size. aw-bits=val (val between 32 and 64, default depends on machine) This decides the address width of the IOVA address space. -device arm-smmuv3,primary-bus=id[,option=...] This is only supported by -machine virt (ARM). primary-bus=id Accepts either the default root complex (pcie.0) or a pxb-pcie based root complex. accel=on|off (default: off) Enables guest to leverage host SMMUv3 features for accel- eration. Enabling accel configures the host SMMUv3 in nested mode to support vfio-pci passthrough. The following options are available when accel=on. Note: 'auto' mode is not currently supported. ril=on|off (default: on) Support for Range Invalidation, which allows the SMMUv3 dri- ver to invalidate TLB entries for a range of IOVAs at once instead of issuing separate commands to invalidate each page. Must match with host SMMUv3 Range Invalidation support. ats=on|off (default: off) Support for Address Translation Services, which enables PCIe devices to cache address translations in their local TLB and reduce latency. Host SMMUv3 must support ATS in order to en- able this feature for the vIOMMU. oas=val (supported values are 44 and 48. default: 44) Sets the Output Address Size in bits. The value set here must be less than or equal to the host SMMUv3's supported OAS, so that the intermediate physical addresses (IPA) consumed by host SMMU for stage-2 translation do not exceed the host's max supported IPA size. ssidsize=val (val between 0 and 20. default: 0) Sets the Substream ID size in bits. When set to a non-zero value, PASID capability is advertised to the vIOMMU and ac- celerated use cases such as Shared Virtual Addressing (SVA) are supported. -device amd-iommu[,option=...] Enables emulation of an AMD-Vi I/O Memory Management Unit (IOMMU). Only available with -machine q35, it supports the following options: dma-remap=on|off (default: off) Support for DMA address translation and access permission checking for guests attaching passthrough devices to paging domains, using the AMD v1 I/O Page Table format. This enables -device vfio-pci,... to work correctly with a guest using the DMA remapping feature of the vIOMMU. intremap=on|off (default: auto) Generic x86 IOMMU functionality implemented by amd-iommu de- vice. Enables interrupt remapping feature in guests, which is also required to enable x2apic support. Currently only available with kernel-irqchip=off|split, it is automatically enabled when either of those modes is in use, and disabled with kernel-irqchip=on. xtsup=on|off (default: off) Interrupt remapping table supports x2apic mode, enabling the use of 128-bit IRTE format with 32-bit destination field by the guest. Required to support routing interrupts to vCPUs with APIC IDs larger than 0xff. -name name Sets the name of the guest. This name will be displayed in the SDL window caption. The name will also be used for the VNC server. Also optionally set the top visible process name in Linux. Naming of in- dividual threads can also be enabled on Linux to aid debugging. -uuid uuid Set system UUID. Block device options The QEMU block device handling options have a long history and have gone through several iterations as the feature set and complexity of the block layer have grown. Many online guides to QEMU often reference older and dep- recated options, which can lead to confusion. The most explicit way to describe disks is to use a combination of -device to specify the hardware device and -blockdev to describe the backend. The device defines what the guest sees and the backend describes how QEMU han- dles the data. It is the only guaranteed stable interface for describing block devices and as such is recommended for management tools and script- ing. The -drive option combines the device and backend into a single command line option which is a more human friendly. There is however no interface stability guarantee although some older board models still need updating to work with the modern blockdev forms. Older options like -hda are essentially macros which expand into -drive op- tions for various drive interfaces. The original forms bake in a lot of as- sumptions from the days when QEMU was emulating a legacy PC, they are not recommended for modern configurations. -fda file -fdb file Use file as floppy disk 0/1 image (see the Disk Images chapter in the System Emulation Users Guide). -hda file -hdb file -hdc file -hdd file Use file as hard disk 0, 1, 2 or 3 image on the default bus of the emulated machine (this is for example the IDE bus on most x86 ma- chines, but it can also be SCSI, virtio or something else on other target architectures). See also the Disk Images chapter in the Sys- tem Emulation Users Guide. -cdrom file Use file as CD-ROM image on the default bus of the emulated machine (which is IDE1 master on x86, so you cannot use -hdc and -cdrom at the same time there). On systems that support it, you can use the host CD-ROM by using /dev/cdrom as filename. -blockdev option[,option[,option[,...]]] Define a new block driver node. Some of the options apply to all block drivers, other options are only accepted for a specific block driver. See below for a list of generic options and options for the most common block drivers. Options that expect a reference to another node (e.g. file) can be given in two ways. Either you specify the node name of an already existing node (file=node-name), or you define a new node inline, adding options for the referenced node after a dot (file.file- name=path,file.aio=native). A block driver node created with -blockdev can be used for a guest device by specifying its node name for the drive property in a -de- vice argument that defines a block device. Valid options for any block driver node: driver Specifies the block driver to use for the given node. node-name This defines the name of the block driver node by which it will be referenced later. The name must be unique, i.e. it must not match the name of a different block driver node, or (if you use -drive as well) the ID of a drive. If no node name is specified, it is automatically gen- erated. The generated node name is not intended to be predictable and changes between QEMU invocations. For the top level, an explicit node name must be speci- fied. read-only Open the node read-only. Guest write attempts will fail. Note that some block drivers support only read-only access, either generally or in certain configurations. In this case, the default value read-only=off does not work and the option must be specified explicitly. auto-read-only If auto-read-only=on is set, QEMU may fall back to read-only usage even when read-only=off is requested, or even switch between modes as needed, e.g. depending on whether the image file is writable or whether a writing user is attached to the node. force-share Override the image locking system of QEMU by forcing the node to utilize weaker shared access for permis- sions where it would normally request exclusive ac- cess. When there is the potential for multiple in- stances to have the same file open (whether this invo- cation of QEMU is the first or the second instance), both instances must permit shared access for the sec- ond instance to succeed at opening the file. Enabling force-share=on requires read-only=on. cache.direct The host page cache can be avoided with cache.di- rect=on. This will attempt to do disk IO directly to the guest's memory. QEMU may still perform an internal copy of the data. cache.no-flush In case you don't care about data integrity over host failures, you can use cache.no-flush=on. This option tells QEMU that it never needs to write any data to the disk but can instead keep things in cache. If any- thing goes wrong, like your host losing power, the disk storage getting disconnected accidentally, etc. your image will most probably be rendered unusable. discard=discard discard is one of "ignore" (or "off") or "unmap" (or "on") and controls whether discard (also known as trim or unmap) requests are ignored or passed to the filesystem. Some machine types may not support dis- card requests. detect-zeroes=detect-zeroes detect-zeroes is "off", "on" or "unmap" and enables the automatic conversion of plain zero writes by the OS to driver specific optimized zero write commands. You may even choose "unmap" if discard is set to "un- map" to allow a zero write to be converted to an unmap operation. Driver-specific options for file This is the protocol-level block driver for accessing regular files. filename The path to the image file in the local filesystem aio Specifies the AIO backend (threads/native/io_uring, default: threads) locking Specifies whether the image file is protected with Linux OFD / POSIX locks. The default is to use the Linux Open File Descriptor API if available, otherwise no lock is applied. (auto/on/off, default: auto) Example: -blockdev driver=file,node-name=disk,filename=disk.img Driver-specific options for raw This is the image format block driver for raw images. It is usually stacked on top of a protocol level block driver such as file. file Reference to or definition of the data source block driver node (e.g. a file driver node) Example 1: -blockdev driver=file,node-name=disk_file,filename=disk.img -blockdev driver=raw,node-name=disk,file=disk_file Example 2: -blockdev driver=raw,node-name=disk,file.driver=file,file.filename=disk.img Driver-specific options for qcow2 This is the image format block driver for qcow2 images. It is usually stacked on top of a protocol level block driver such as file. file Reference to or definition of the data source block driver node (e.g. a file driver node) backing Reference to or definition of the backing file block device (default is taken from the image file). It is allowed to pass null here in order to disable the de- fault backing file. lazy-refcounts Whether to enable the lazy refcounts feature (on/off; default is taken from the image file) cache-size The maximum total size of the L2 table and refcount block caches in bytes (default: the sum of l2-cache-size and refcount-cache-size) l2-cache-size The maximum size of the L2 table cache in bytes (de- fault: if cache-size is not specified - 32M on Linux platforms, and 8M on non-Linux platforms; otherwise, as large as possible within the cache-size, while per- mitting the requested or the minimal refcount cache size) refcount-cache-size The maximum size of the refcount block cache in bytes (default: 4 times the cluster size; or if cache-size is specified, the part of it which is not used for the L2 cache) cache-clean-interval Clean unused entries in the L2 and refcount caches. The interval is in seconds. The default value is 600 on supporting platforms, and 0 on other platforms. Setting it to 0 disables this feature. pass-discard-request Whether discard requests to the qcow2 device should be forwarded to the data source (on/off; default: on if discard=unmap is specified, off otherwise) pass-discard-snapshot Whether discard requests for the data source should be issued when a snapshot operation (e.g. deleting a snapshot) frees clusters in the qcow2 file (on/off; default: on) pass-discard-other Whether discard requests for the data source should be issued on other occasions where a cluster gets freed (on/off; default: off) discard-no-unref When enabled, data clusters will remain preallocated when they are no longer used, e.g. because they are discarded or converted to zero clusters. As usual, whether the old data is discarded or kept on the pro- tocol level (i.e. in the image file) depends on the setting of the pass-discard-request option. Keeping the clusters preallocated prevents qcow2 fragmentation that would otherwise be caused by freeing and re-allo- cating them later. Besides potential performance degradation, such fragmentation can lead to increased allocation of clusters past the end of the image file, resulting in image files whose file length can grow much larger than their guest disk size would suggest. If image file length is of concern (e.g. when storing qcow2 images directly on block devices), you should consider enabling this option. overlap-check Which overlap checks to perform for writes to the im- age (none/constant/cached/all; default: cached). For details or finer granularity control refer to the QAPI documentation of blockdev-add. Example 1: -blockdev driver=file,node-name=my_file,filename=/tmp/disk.qcow2 -blockdev driver=qcow2,node-name=hda,file=my_file,overlap-check=none,cache-size=16777216 Example 2: -blockdev driver=qcow2,node-name=disk,file.driver=http,file.filename=http://example.com/image.qcow2 Driver-specific options for other drivers Please refer to the QAPI documentation of the blockdev-add QMP command. -drive option[,option[,option[,...]]] Define a new drive. This includes creating a block driver node (the backend) as well as a guest device, and is mostly a shortcut for defining the corresponding -blockdev and -device options. -drive accepts all options that are accepted by -blockdev. In addi- tion, it knows the following options: file=file This option defines which disk image (see the Disk Images chapter in the System Emulation Users Guide) to use with this drive. If the filename contains comma, you must double it (for instance, "file=my,,file" to use file "my,file"). Special files such as iSCSI devices can be specified using protocol specific URLs. See the section for "Device URL Syn- tax" for more information. if=interface This option defines on which type on interface the drive is connected. Available types are: ide, scsi, sd, mtd, floppy, pflash, virtio, none. bus=bus,unit=unit These options define where is connected the drive by defining the bus number and the unit id. index=index This option defines where the drive is connected by using an index in the list of available connectors of a given inter- face type. media=media This option defines the type of the media: disk or cdrom. snapshot=snapshot snapshot is "on" or "off" and controls snapshot mode for the given drive (see -snapshot). cache=cache cache is "none", "writeback", "unsafe", "directsync" or "writethrough" and controls how the host cache is used to ac- cess block data. This is a shortcut that sets the cache.di- rect and cache.no-flush options (as in -blockdev), and addi- tionally cache.writeback, which provides a default for the write-cache option of block guest devices (as in -device). The modes correspond to the following settings: +--------------+-----------------+--------------+----------------+ | | cache.writeback | cache.direct | cache.no-flush | +--------------+-----------------+--------------+----------------+ | writeback | on | off | off | +--------------+-----------------+--------------+----------------+ | none | on | on | off | +--------------+-----------------+--------------+----------------+ | writethrough | off | off | off | +--------------+-----------------+--------------+----------------+ | directsync | off | on | off | +--------------+-----------------+--------------+----------------+ | unsafe | on | off | on | +--------------+-----------------+--------------+----------------+ The default mode is cache=writeback. aio=aio aio is "threads", "native", or "io_uring" and selects between pthread based disk I/O, native Linux AIO, or Linux io_uring API. format=format Specify which disk format will be used rather than detecting the format. Can be used to specify format=raw to avoid inter- preting an untrusted format header. werror=action,rerror=action Specify which action to take on write and read errors. Valid actions are: "ignore" (ignore the error and try to continue), "stop" (pause QEMU), "report" (report the error to the guest), "enospc" (pause QEMU only if the host disk is full; report the error to the guest otherwise). The default setting is werror=enospc and rerror=report. copy-on-read=copy-on-read copy-on-read is "on" or "off" and enables whether to copy read backing file sectors into the image file. bps=b,bps_rd=r,bps_wr=w Specify bandwidth throttling limits in bytes per second, ei- ther for all request types or for reads or writes only. Small values can lead to timeouts or hangs inside the guest. A safe minimum for disks is 2 MiB/s. bps_max=bm,bps_rd_max=rm,bps_wr_max=wm Specify bursts in bytes per second, either for all request types or for reads or writes only. Bursts allow the guest I/O to spike above the limit temporarily. iops=i,iops_rd=r,iops_wr=w Specify request rate limits in requests per second, either for all request types or for reads or writes only. iops_max=bm,iops_rd_max=rm,iops_wr_max=wm Specify bursts in requests per second, either for all request types or for reads or writes only. Bursts allow the guest I/O to spike above the limit temporarily. iops_size=is Let every is bytes of a request count as a new request for iops throttling purposes. Use this option to prevent guests from circumventing iops limits by sending fewer but larger requests. group=g Join a throttling quota group with given name g. All drives that are members of the same group are accounted for to- gether. Use this option to prevent guests from circumventing throttling limits by using many small disks instead of a sin- gle larger disk. By default, the cache.writeback=on mode is used. It will report data writes as completed as soon as the data is present in the host page cache. This is safe as long as your guest OS makes sure to correctly flush disk caches where needed. If your guest OS does not handle volatile disk write caches correctly and your host crashes or loses power, then the guest may experience data corruption. For such guests, you should consider using cache.writeback=off. This means that the host page cache will be used to read and write data, but write notification will be sent to the guest only after QEMU has made sure to flush each write to the disk. Be aware that this has a major impact on performance. When using the -snapshot option, unsafe caching is always used. Copy-on-read avoids accessing the same backing file sectors repeat- edly and is useful when the backing file is over a slow network. By default copy-on-read is off. Instead of -cdrom you can use: qemu-system-x86_64 -drive file=file,index=2,media=cdrom Instead of -hda, -hdb, -hdc, -hdd, you can use: qemu-system-x86_64 -drive file=file,index=0,media=disk qemu-system-x86_64 -drive file=file,index=1,media=disk qemu-system-x86_64 -drive file=file,index=2,media=disk qemu-system-x86_64 -drive file=file,index=3,media=disk You can open an image using pre-opened file descriptors from an fd set: qemu-system-x86_64 \ -add-fd fd=3,set=2,opaque="rdwr:/path/to/file" \ -add-fd fd=4,set=2,opaque="rdonly:/path/to/file" \ -drive file=/dev/fdset/2,index=0,media=disk You can connect a CDROM to the slave of ide0: qemu-system-x86_64 -drive file=file,if=ide,index=1,media=cdrom If you don't specify the "file=" argument, you define an empty drive: qemu-system-x86_64 -drive if=ide,index=1,media=cdrom Instead of -fda, -fdb, you can use: qemu-system-x86_64 -drive file=file,index=0,if=floppy qemu-system-x86_64 -drive file=file,index=1,if=floppy By default, interface is "ide" and index is automatically incre- mented: qemu-system-x86_64 -drive file=a -drive file=b is interpreted like: qemu-system-x86_64 -hda a -hdb b -mtdblock file Use file as on-board Flash memory image. -sd file Use file as SecureDigital card image. -snapshot Write to temporary files instead of disk image files. In this case, the raw disk image you use is not written back. You can however force the write back by pressing C-a s (see the Disk Images chapter in the System Emulation Users Guide). WARNING: snapshot is incompatible with -blockdev (instead use qemu-img to manually create snapshot images to attach to your blockdev). If you have mixed -blockdev and -drive declarations you can use the 'snapshot' property on your drive declarations instead of this global option. -fsdev local,id=id,path=path,security_model=security_model [,write- out=writeout][,readonly=on][,fmode=fmode][,dmode=dmode] [,throttling.op- tion=value[,throttling.option=value[,...]]] -fsdev synth,id=id[,readonly=on] Define a new file system device. Valid options are: local Accesses to the filesystem are done by QEMU. synth Synthetic filesystem, only used by QTests. id=id Specifies identifier for this device. path=path Specifies the export path for the file system device. Files under this path will be available to the 9p client on the guest. security_model=security_model Specifies the security model to be used for this export path. Supported security models are "passthrough", "mapped-xattr", "mapped-file" and "none". In "passthrough" security model, files are stored using the same credentials as they are cre- ated on the guest. This requires QEMU to run as root. In "mapped-xattr" security model, some of the file attributes like uid, gid, mode bits and link target are stored as file attributes. For "mapped-file" these attributes are stored in the hidden .virtfs_metadata directory. Directories exported by this security model cannot interact with other unix tools. "none" security model is same as passthrough except the sever won't report failures if it fails to set file attributes like ownership. Security model is mandatory only for local fs- driver. writeout=writeout This is an optional argument. The only supported value is "immediate". This means that host page cache will be used to read and write data but write notification will be sent to the guest only when the data has been reported as written by the storage subsystem. readonly=on Enables exporting 9p share as a readonly mount for guests. By default read-write access is given. fmode=fmode Specifies the default mode for newly created files on the host. Works only with security models "mapped-xattr" and "mapped-file". dmode=dmode Specifies the default mode for newly created directories on the host. Works only with security models "mapped-xattr" and "mapped-file". throttling.bps-total=b,throttling.bps-read=r,throttling.bps-write=w Specify bandwidth throttling limits in bytes per second, ei- ther for all request types or for reads or writes only. throttling.bps-total-max=bm,bps-read-max=rm,bps-write-max=wm Specify bursts in bytes per second, either for all request types or for reads or writes only. Bursts allow the guest I/O to spike above the limit temporarily. throttling.iops-total=i,throttling.iops-read=r, throt- tling.iops-write=w Specify request rate limits in requests per second, either for all request types or for reads or writes only. throttling.iops-total-max=im,throttling.iops-read-max=irm, throt- tling.iops-write-max=iwm Specify bursts in requests per second, either for all request types or for reads or writes only. Bursts allow the guest I/O to spike above the limit temporarily. throttling.iops-size=is Let every is bytes of a request count as a new request for iops throttling purposes. -fsdev option is used along with -device driver "virtio-9p-...". -device virtio-9p-type,fsdev=id,mount_tag=mount_tag Options for virtio-9p-... driver are: type Specifies the variant to be used. Supported values are "pci", "ccw" or "device", depending on the machine type. fsdev=id Specifies the id value specified along with -fsdev option. mount_tag=mount_tag Specifies the tag name to be used by the guest to mount this export point. -virtfs local,path=path,mount_tag=mount_tag ,security_model=secu- rity_model[,writeout=writeout][,readonly=on] [,fmode=fmode][,dmode=dmode][,multidevs=multidevs] -virtfs synth,mount_tag=mount_tag Define a new virtual filesystem device and expose it to the guest using a virtio-9p-device (a.k.a. 9pfs), which essentially means that a certain directory on host is made directly accessible by guest as a pass-through file system by using the 9P network protocol for com- munication between host and guests, if desired even accessible, shared by several guests simultaneously. Note that -virtfs is actually just a convenience shortcut for its generalized form -fsdev -device virtio-9p-pci. The general form of pass-through file system options are: local Accesses to the filesystem are done by QEMU. synth Synthetic filesystem, only used by QTests. id=id Specifies identifier for the filesystem device path=path Specifies the export path for the file system device. Files under this path will be available to the 9p client on the guest. security_model=security_model Specifies the security model to be used for this export path. Supported security models are "passthrough", "mapped-xattr", "mapped-file" and "none". In "passthrough" security model, files are stored using the same credentials as they are cre- ated on the guest. This requires QEMU to run as root. In "mapped-xattr" security model, some of the file attributes like uid, gid, mode bits and link target are stored as file attributes. For "mapped-file" these attributes are stored in the hidden .virtfs_metadata directory. Directories exported by this security model cannot interact with other unix tools. "none" security model is same as passthrough except the sever won't report failures if it fails to set file attributes like ownership. Security model is mandatory only for local fs- driver. writeout=writeout This is an optional argument. The only supported value is "immediate". This means that host page cache will be used to read and write data but write notification will be sent to the guest only when the data has been reported as written by the storage subsystem. readonly=on Enables exporting 9p share as a readonly mount for guests. By default read-write access is given. fmode=fmode Specifies the default mode for newly created files on the host. Works only with security models "mapped-xattr" and "mapped-file". dmode=dmode Specifies the default mode for newly created directories on the host. Works only with security models "mapped-xattr" and "mapped-file". mount_tag=mount_tag Specifies the tag name to be used by the guest to mount this export point. multidevs=remap|forbid|warn Specifies how to deal with multiple devices being shared with the same 9p export in order to avoid file ID collisions on guest. Supported behaviours are either "remap" (default), "forbid" or "warn". remap : assumes the possibility that more than one device is shared with the same 9p export. Therefore inode numbers from host are remapped for guest in a way that would prevent file ID collisions on guest. Remapping inodes in such cases is re- quired because the original device IDs from host are never passed and exposed on guest. Instead all files of an export shared with virtfs always share the same device ID on guest. So two files with identical inode numbers but from actually different devices on host would otherwise cause a file ID collision and hence potential severe misbehaviours on guest. warn : virtfs 9p expects only one device to be shared with the same export. If however more than one device is shared and accessed via the same 9p export then only a warning mes- sage is logged (once) by qemu on host side. No further action is performed in this case that would prevent file ID colli- sions on guest. This could thus lead to severe misbehaviours in this case like wrong files being accessed and data corrup- tion on the exported tree. forbid : assumes like "warn" that only one device is shared by the same 9p export, however it will not only log a warning message but also deny access to additional devices on guest. Note though that "forbid" does currently not block all possi- ble file access operations (e.g. readdir() would still return entries from other devices). -iscsi Configure iSCSI session parameters. USB convenience options -usb Enable USB emulation on machine types with an on-board USB host con- troller (if not enabled by default). Note that on-board USB host controllers may not support USB 3.0. In this case -device qemu-xhci can be used instead on machines with PCI. -usbdevice devname Add the USB device devname, and enable an on-board USB controller if possible and necessary (just like it can be done via -machine usb=on). Note that this option is mainly intended for the user's convenience only. More fine-grained control can be achieved by se- lecting a USB host controller (if necessary) and the desired USB de- vice via the -device option instead. For example, instead of using -usbdevice mouse it is possible to use -device qemu-xhci -device usb-mouse to connect the USB mouse to a USB 3.0 controller instead (at least on machines that support PCI and do not have an USB con- troller enabled by default yet). For more details, see the chapter about Connecting USB devices in the System Emulation Users Guide. Possible devices for devname are: braille Braille device. This will use BrlAPI to display the braille output on a real or fake device (i.e. it also creates a cor- responding braille chardev automatically beside the usb-braille USB device). keyboard Standard USB keyboard. Will override the PS/2 keyboard (if present). mouse Virtual Mouse. This will override the PS/2 mouse emulation when activated. tablet Pointer device that uses absolute coordinates (like a touch- screen). This means QEMU is able to report the mouse position without having to grab the mouse. Also overrides the PS/2 mouse emulation when activated. wacom-tablet Wacom PenPartner USB tablet. Display options -display type Select type of display to use. This may also influence the default audio backend selection. Use -display help to list the available display types. Valid values for type are spice-app[,gl=on|off] Start QEMU as a Spice server and launch the default Spice client application. The Spice server will redirect the serial consoles and QEMU monitors. (Since 4.0) dbus Export the display over D-Bus interfaces. (Since 7.0) If no audio backend is specified and the dbus display backend is specified, the dbus audio backend is used by default. The connection is registered with the "org.qemu" name (and queued when already owned). addr=<dbusaddr> : D-Bus bus address to connect to. p2p=yes|no : Use peer-to-peer connection, accepted via QMP add_client. gl=on|off|core|es : Use OpenGL for rendering (the D-Bus in- terface will share framebuffers with DMABUF file descrip- tors). sdl Display video output via SDL (usually in a separate graphics window; see the SDL documentation for other possibilities). Valid parameters are: grab-mod=<mods> : Used to select the modifier keys for tog- gling the mouse grabbing in conjunction with the "g" key. <mods> can be either lshift-lctrl-lalt or rctrl. gl=on|off|core|es : Use OpenGL for displaying show-cursor=on|off : Force showing the mouse cursor window-close=on|off : Allow to quit qemu with window close button gtk Display video output in a GTK window. This interface provides drop-down menus and other UI elements to configure and con- trol the VM during runtime. Valid parameters are: full-screen=on|off : Start in fullscreen mode gl=on|off : Use OpenGL for displaying grab-on-hover=on|off : Grab keyboard input on mouse hover show-tabs=on|off (Display the tab bar for switching between the) various graphical interfaces (e.g. VGA and virtual console character devices) by default. show-cursor=on|off : Force showing the mouse cursor window-close=on|off : Allow to quit qemu with window close button show-menubar=on|off : Display the main window menubar, de- faults to "on" zoom-to-fit=on|off (Expand video output to the window size,) defaults to "off" curses[,charset=<encoding>] Display video output via curses. For graphics device models which support a text mode, QEMU can display this output using a curses/ncurses interface. Nothing is displayed when the graphics device is in graphical mode or if the graphics de- vice does not support a text mode. Generally only the VGA de- vice models support text mode. The font charset used by the guest can be specified with the charset option, for example charset=CP850 for IBM CP850 encoding. The default is CP437. cocoa Display video output in a Cocoa window. Mac only. This inter- face provides drop-down menus and other UI elements to con- figure and control the VM during runtime. Valid parameters are: full-grab=on|off (Capture all key presses, including system combos.) This requires accessibility permissions, since it per- forms a global grab on key events. (default: off) See - https://support.ap- ple.com/en-in/guide/mac-help/mh32356/mac swap-opt-cmd=on|off (Swap the Option and Command keys so that their) key codes match their position on non-Mac keyboards and you can use Meta/Super and Alt where you expect them. (default: off) show-cursor=on|off : Force showing the mouse cursor left-command-key=on|off : Disable forwarding left command key to host full-screen=on|off : Start in fullscreen mode zoom-to-fit=on|off (Expand video output to the window size,) defaults to "off" egl-headless[,rendernode=<file>] Offload all OpenGL operations to a local DRI device. For any graphical display, this display needs to be paired with ei- ther VNC or SPICE displays. vnc=<display> Start a VNC server on display <display> none Do not display video output. The guest will still see an emu- lated graphics card, but its output will not be displayed to the QEMU user. This option differs from the -nographic option in that it only affects what is done with video output; -no- graphic also changes the destination of the serial and paral- lel port data. -nographic Normally, if QEMU is compiled with graphical window support, it dis- plays output such as guest graphics, guest console, and the QEMU monitor in a window. With this option, you can totally disable graphical output so that QEMU is a simple command line application. The emulated serial port is redirected on the console and muxed with the monitor (unless redirected elsewhere explicitly). Therefore, you can still use QEMU to debug a Linux kernel with a serial console. Use C-a h for help on switching between the console and monitor. -spice option[,option[,...]] Enable the spice remote desktop protocol. Valid options are port=<nr> Set the TCP port spice is listening on for plaintext chan- nels. addr=<addr> Set the IP address spice is listening on. Default is any ad- dress. ipv4=on|off; ipv6=on|off; unix=on|off Force using the specified IP version. password-secret=<secret-id> Set the ID of the secret object containing the password you need to authenticate. sasl=on|off Require that the client use SASL to authenticate with the spice. The exact choice of authentication method used is controlled from the system / user's SASL configuration file for the 'qemu' service. This is typically found in /etc/sasl2/qemu.conf. If running QEMU as an unprivileged user, an environment variable SASL_CONF_PATH can be used to make it search alternate locations for the service config. While some SASL auth methods can also provide data encryption (eg GSSAPI), it is recommended that SASL always be combined with the 'tls' and 'x509' settings to enable use of SSL and server certificates. This ensures a data encryption prevent- ing compromise of authentication credentials. disable-ticketing=on|off Allow client connects without authentication. disable-copy-paste=on|off Disable copy paste between the client and the guest. disable-agent-file-xfer=on|off Disable spice-vdagent based file-xfer between the client and the guest. tls-port=<nr> Set the TCP port spice is listening on for encrypted chan- nels. x509-dir=<dir> Set the x509 file directory. Expects same filenames as -vnc $display,x509=$dir x509-key-file=<file>; x509-key-password=<file>; x509-cert-file=<file>; x509-cacert-file=<file>; x509-dh-key-file=<file> The x509 file names can also be configured individually. tls-ciphers=<list> Specify which ciphers to use. tls-channel=main|display|cursor|inputs|record|playback; plain- text-channel=main|display|cursor|inputs|record|playback Force specific channel to be used with or without TLS encryp- tion. The options can be specified multiple times to config- ure multiple channels. The special name "default" can be used to set the default mode. For channels which are not explic- itly forced into one mode the spice client is allowed to pick tls/plaintext as he pleases. image-compression=auto_glz|auto_lz|quic|glz|lz|off Configure image compression (lossless). Default is auto_glz. jpeg-wan-compression=auto|never|always; zlib-glz-wan-compres- sion=auto|never|always Configure wan image compression (lossy for slow links). De- fault is auto. streaming-video=off|all|filter Configure video stream detection. Default is off. agent-mouse=on|off Enable/disable passing mouse events via vdagent. Default is on. playback-compression=on|off Enable/disable audio stream compression (using celt 0.5.1). Default is on. seamless-migration=on|off Enable/disable spice seamless migration. Default is off. video-codec=<codec> Provide the preferred codec the Spice server should use with the Gstreamer encoder. This option is only relevant when gl=on is specified. If no codec is provided, then the codec gstreamer:h264 would be used as default. And, for the case where gl=off, the default codec to be used is determined by the Spice server. max-refresh-rate=rate Provide the maximum refresh rate (or FPS) at which the encod- ing requests should be sent to the Spice server. Default would be 30. gl=on|off Enable/disable OpenGL context. Default is off. rendernode=<file> DRM render node for OpenGL rendering. If not specified, it will pick the first available. (Since 2.9) -vga type Select type of VGA card to emulate. Valid values for type are cirrus Cirrus Logic GD5446 Video card. All Windows versions starting from Windows 95 should recognize and use this graphic card. For optimal performances, use 16 bit color depth in the guest and the host OS. (This card was the default before QEMU 2.2) std Standard VGA card with Bochs VBE extensions. If your guest OS supports the VESA 2.0 VBE extensions (e.g. Windows XP) and if you want to use high resolution modes (>= 1280x1024x16) then you should use this option. (This card is the default since QEMU 2.2) vmware VMWare SVGA-II compatible adapter. Use it if you have suffi- ciently recent XFree86/XOrg server or Windows guest with a driver for this card. qxl QXL paravirtual graphic card. It is VGA compatible (including VESA 2.0 VBE support). Works best with qxl guest drivers in- stalled though. Recommended choice when using the spice pro- tocol. tcx (sun4m only) Sun TCX framebuffer. This is the default frame- buffer for sun4m machines and offers both 8-bit and 24-bit colour depths at a fixed resolution of 1024x768. cg3 (sun4m only) Sun cgthree framebuffer. This is a simple 8-bit framebuffer for sun4m machines available in both 1024x768 (OpenBIOS) and 1152x900 (OBP) resolutions aimed at people wishing to run older Solaris versions. virtio Virtio VGA card. none Disable VGA card. -full-screen Start in full screen. -g widthxheight[xdepth] Set the initial graphical resolution and depth (PPC, SPARC only). For PPC the default is 800x600x32. For SPARC with the TCX graphics device, the default is 1024x768x8 with the option of 1024x768x24. For cgthree, the default is 1024x768x8 with the option of 1152x900x8 for people who wish to use OBP. -vnc display[,option[,option[,...]]] Normally, if QEMU is compiled with graphical window support, it dis- plays output such as guest graphics, guest console, and the QEMU monitor in a window. With this option, you can have QEMU listen on VNC display display and redirect the VGA display over the VNC ses- sion. It is very useful to enable the usb tablet device when using this option (option -device usb-tablet). When using the VNC display, you must use the -k parameter to set the keyboard layout if you are not using en-us. Valid syntax for the display is to=L With this option, QEMU will try next available VNC displays, until the number L, if the originally defined "-vnc display" is not available, e.g. port 5900+display is already used by another application. By default, to=0. host:d TCP connections will only be allowed from host on display d. By convention the TCP port is 5900+d. Optionally, host can be omitted in which case the server will accept connections from any host. unix:path Connections will be allowed over UNIX domain sockets where path is the location of a unix socket to listen for connec- tions on. none VNC is initialized but not started. The monitor change com- mand can be used to later start the VNC server. Following the display value there may be one or more option flags separated by commas. Valid options are reverse=on|off Connect to a listening VNC client via a "reverse" connection. The client is specified by the display. For reverse network connections (host:d,``reverse``), the d argument is a TCP port number, not a display number. websocket=on|off Opens an additional TCP listening port dedicated to VNC Web- socket connections. If a bare websocket option is given, the Websocket port is 5700+display. An alternative port can be specified with the syntax websocket=port. If host is specified connections will only be allowed from this host. It is possible to control the websocket listen ad- dress independently, using the syntax websocket=host:port. Websocket could be allowed over UNIX domain socket, using the syntax websocket=unix:path, where path is the location of a unix socket to listen for connections on. If no TLS credentials are provided, the websocket connection runs in unencrypted mode. If TLS credentials are provided, the websocket connection requires encrypted client connec- tions. password=on|off Require that password based authentication is used for client connections. The password must be set separately using the set_password command in the QEMU Monitor. The syntax to change your pass- word is: set_password <protocol> <password> where <protocol> could be either "vnc" or "spice". If you would like to change <protocol> password expiration, you should use expire_password <protocol> <expiration-time> where expiration time could be one of the following options: now, never, +seconds or UNIX time of expiration, e.g. +60 to make password expire in 60 seconds, or 1335196800 to make password expire on "Mon Apr 23 12:00:00 EDT 2012" (UNIX time for this date and time). You can also use keywords "now" or "never" for the expiration time to allow <protocol> password to expire immediately or never expire. password-secret=<secret-id> Require that password based authentication is used for client connections, using the password provided by the secret object identified by secret-id. tls-creds=ID Provides the ID of a set of TLS credentials to use to secure the VNC server. They will apply to both the normal VNC server socket and the websocket socket (if enabled). Setting TLS credentials will cause the VNC server socket to enable the VeNCrypt auth mechanism. The credentials should have been previously created using the -object tls-creds argument. tls-authz=ID Provides the ID of the QAuthZ authorization object against which the client's x509 distinguished name will validated. This object is only resolved at time of use, so can be deleted and recreated on the fly while the VNC server is ac- tive. If missing, it will default to denying access. sasl=on|off Require that the client use SASL to authenticate with the VNC server. The exact choice of authentication method used is controlled from the system / user's SASL configuration file for the 'qemu' service. This is typically found in /etc/sasl2/qemu.conf. If running QEMU as an unprivileged user, an environment variable SASL_CONF_PATH can be used to make it search alternate locations for the service config. While some SASL auth methods can also provide data encryption (eg GSSAPI), it is recommended that SASL always be combined with the 'tls' and 'x509' settings to enable use of SSL and server certificates. This ensures a data encryption prevent- ing compromise of authentication credentials. See the VNC se- curity section in the System Emulation Users Guide for de- tails on using SASL authentication. sasl-authz=ID Provides the ID of the QAuthZ authorization object against which the client's SASL username will validated. This object is only resolved at time of use, so can be deleted and recre- ated on the fly while the VNC server is active. If missing, it will default to denying access. acl=on|off Legacy method for enabling authorization of clients against the x509 distinguished name and SASL username. It results in the creation of two authz-list objects with IDs of vnc.user- name and vnc.x509dname. The rules for these objects must be configured with the HMP ACL commands. This option is deprecated and should no longer be used. The new sasl-authz and tls-authz options are a replacement. lossy=on|off Enable lossy compression methods (gradient, JPEG, ...). If this option is set, VNC client may receive lossy framebuffer updates depending on its encoding settings. Enabling this op- tion can save a lot of bandwidth at the expense of quality. non-adaptive=on|off Disable adaptive encodings. Adaptive encodings are enabled by default. An adaptive encoding will try to detect frequently updated screen regions, and send updates in these regions us- ing a lossy encoding (like JPEG). This can be really helpful to save bandwidth when playing videos. Disabling adaptive en- codings restores the original static behavior of encodings like Tight. share=allow-exclusive|force-shared|ignore Set display sharing policy. 'allow-exclusive' allows clients to ask for exclusive access. As suggested by the rfb spec this is implemented by dropping other connections. Connecting multiple clients in parallel requires all clients asking for a shared session (vncviewer: -shared switch). This is the de- fault. 'force-shared' disables exclusive client access. Use- ful for shared desktop sessions, where you don't want someone forgetting specify -shared disconnect everybody else. 'ig- nore' completely ignores the shared flag and allows everybody connect unconditionally. Doesn't conform to the rfb spec but is traditional QEMU behavior. key-delay-ms Set keyboard delay, for key down and key up events, in mil- liseconds. Default is 10. Keyboards are low-bandwidth de- vices, so this slowdown can help the device and guest to keep up and not lose events in case events are arriving in bulk. Possible causes for the latter are flaky network connections, or scripts for automated testing. audiodev=audiodev Use the specified audiodev when the VNC client requests audio transmission. When not using an -audiodev argument, this op- tion must be omitted, otherwise is must be present and spec- ify a valid audiodev. power-control=on|off Permit the remote client to issue shutdown, reboot or reset power control requests. i386 target only -win2k-hack Use it when installing Windows 2000 to avoid a disk full bug. After Windows 2000 is installed, you no longer need this option (this op- tion slows down the IDE transfers). Synonym of -global ide-de- vice.win2k-install-hack=on. -no-fd-bootchk Disable boot signature checking for floppy disks in BIOS. May be needed to boot from old floppy disks. Synonym of -m fd-bootchk=off. -acpitable [sig=str][,rev=n][,oem_id=str][,oem_table_id=str][,oem_rev=n] [,asl_compiler_id=str][,asl_compiler_rev=n][,data=file1[:file2]...] Add ACPI table with specified header fields and context from speci- fied files. For file=, take whole ACPI table from the specified files, including all ACPI headers (possible overridden by other op- tions). For data=, only data portion of the table is used, all header information is specified in the command line. If a SLIC table is supplied to QEMU, then the SLIC's oem_id and oem_table_id fields will override the same in the RSDT and the FADT (a.k.a. FACP), in order to ensure the field matches required by the Microsoft SLIC spec and the ACPI spec. -smbios file=binary Load SMBIOS entry from binary file. -smbios type=0[,vendor=str][,version=str][,date=str][,re- lease=%d.%d][,uefi=on|off] Specify SMBIOS type 0 fields -smbios type=1[,manufacturer=str][,product=str][,version=str][,ser- ial=str][,uuid=uuid][,sku=str][,family=str] Specify SMBIOS type 1 fields -smbios type=2[,manufacturer=str][,product=str][,version=str][,ser- ial=str][,asset=str][,location=str] Specify SMBIOS type 2 fields -smbios type=3[,manufacturer=str][,version=str][,serial=str][,as- set=str][,sku=str] Specify SMBIOS type 3 fields -smbios type=4[,sock_pfx=str][,manufacturer=str][,version=str][,ser- ial=str][,asset=str][,part=str][,processor-family=%d][,processor-id=%d] Specify SMBIOS type 4 fields -smbios type=9[,slot_designa- tion=str][,slot_type=%d][,slot_data_bus_width=%d][,current_us- age=%d][,slot_length=%d][,slot_id=%d][,slot_characteris- tics1=%d][,slot_characteristics12=%d][,pci_device=str] Specify SMBIOS type 9 fields -smbios type=11[,value=str][,path=filename] Specify SMBIOS type 11 fields This argument can be repeated multiple times, and values are added in the order they are parsed. Applications intending to use OEM strings data are encouraged to use their application name as a pre- fix for the value string. This facilitates passing information for multiple applications concurrently. The value=str syntax provides the string data inline, while the path=filename syntax loads data from a file on disk. Note that the file is not permitted to contain any NUL bytes. Both the value and path options can be repeated multiple times and will be added to the SMBIOS table in the order in which they appear. Note that on the x86 architecture, the total size of all SMBIOS ta- bles is limited to 65535 bytes. Thus the OEM strings data is not suitable for passing large amounts of data into the guest. Instead it should be used as a indicator to inform the guest where to locate the real data set, for example, by specifying the serial ID of a block device. An example passing three strings is -smbios type=11,value=cloud-init:ds=nocloud-net;s=http://10.10.0.1:8000/,\ value=anaconda:method=http://dl.fedoraproject.org/pub/fedora/linux/releases/25/x86_64/os,\ path=/some/file/with/oemstringsdata.txt In the guest OS this is visible with the dmidecode command $ dmidecode -t 11 Handle 0x0E00, DMI type 11, 5 bytes OEM Strings String 1: cloud-init:ds=nocloud-net;s=http://10.10.0.1:8000/ String 2: anaconda:method=http://dl.fedoraproject.org/pub/fedora/linux/releases/25/x86_64/os String 3: myapp:some extra data -smbios type=17[,loc_pfx=str][,bank=str][,manufacturer=str][,ser- ial=str][,asset=str][,part=str][,speed=%d] Specify SMBIOS type 17 fields -smbios type=41[,designation=str][,kind=str][,instance=%d][,pcidev=str] Specify SMBIOS type 41 fields This argument can be repeated multiple times. Its main use is to allow network interfaces be created as enoX on Linux, with X being the instance number, instead of the name depending on the interface position on the PCI bus. Here is an example of use: -netdev user,id=internet \ -device virtio-net-pci,mac=50:54:00:00:00:42,netdev=internet,id=internet-dev \ -smbios type=41,designation='Onboard LAN',instance=1,kind=ethernet,pcidev=internet-dev In the guest OS, the device should then appear as eno1: ..parsed-literal: $ ip -brief l lo UNKNOWN 00:00:00:00:00:00 <LOOPBACK,UP,LOWER_UP> eno1 UP 50:54:00:00:00:42 <BROADCAST,MULTICAST,UP,LOWER_UP> Currently, the PCI device has to be attached to the root bus. Network options -nic [tap|passt|bridge|user|l2tpv3|vde|netmap|af-xdp|vhost-user|socket][,...][,mac=macaddr][,model=mn] This option is a shortcut for configuring both the on-board (de- fault) guest NIC hardware and the host network backend in one go. The host backend options are the same as with the corresponding -netdev options below. The guest NIC model can be set with model=modelname. Use model=help to list the available device types. The hardware MAC address can be set with mac=macaddr. The following two example do exactly the same, to show how -nic can be used to shorten the command line length: qemu-system-x86_64 -netdev user,id=n1,ipv6=off -device e1000,netdev=n1,mac=52:54:98:76:54:32 qemu-system-x86_64 -nic user,ipv6=off,model=e1000,mac=52:54:98:76:54:32 -nic none Indicate that no network devices should be configured. It is used to override the default configuration (default NIC with "user" host network backend) which is activated if no other networking options are provided. -netdev passt,id=str[,option][,...] Configure a passt network backend which requires no administrator privilege to run. Valid options are: id=id Assign symbolic name for use in monitor commands. path=file Filename of the passt program to run. If it is not provided, passt command will be started with the help of the PATH envi- ronment variable. quiet=on|off By default, quiet=on to disable informational message from passt. quiet=on is passed as --quiet to passt. vhost-user=on|off By default, vhost-user=off and QEMU uses the stream network backend to communicate with passt. If vhost-user=on, passt is started with --vhost-user and QEMU uses the vhost-user net- work backend to communicate with passt. @mtu Assign MTU via DHCP/NDP address IPv4 or IPv6 address netmask IPv4 mask mac source MAC address gateway IPv4 or IPv6 address as gateway interface Interface for addresses and routes outbound Bind to address as outbound source outbound-if4 Bind to outbound interface for IPv4 outbound-if6 Bind to outbound interface for IPv6 dns IPv4 or IPv6 address as DNS search Search domains fqdn FQDN to configure client with dhcp-dns Enable/disable DNS list in DHCP/DHCPv6/NDP dhcp-search Enable/disable list in DHCP/DHCPv6/NDP map-host-loopback Address to refer to host map-guest-addr Addr to translate to guest's address dns-forward Forward DNS queries sent to dns-host Host nameserver to direct queries to tcp Enable/disable TCP udp Enable/disable UDP icmp Enable/disable ICMP dhcp Enable/disable DHCP ndp Enable/disable NDP dhcpv6 Enable/disable DHCPv6 ra Enable/disable route advertisements freebind Bind to any address for forwarding ipv4 Enable/disable IPv4 ipv6 Enable/disable IPv6 tcp-ports TCP ports to forward udp-ports UDP ports to forward param=string string will be passed to passt as a command line parameter, we can have multiple occurrences of the param parameter to pass multiple parameters to passt. For instance, to pass --trace --log=trace.log: qemu-system-x86_64 -nic passt,param=--trace,param=--log=trace.log -netdev user,id=id[,option][,option][,...] Configure user mode host network backend which requires no adminis- trator privilege to run. Valid options are: id=id Assign symbolic name for use in monitor commands. ipv4=on|off and ipv6=on|off Specify that either IPv4 or IPv6 must be enabled. If neither is specified both protocols are enabled. net=addr[/mask] Set IP network address the guest will see. Optionally specify the netmask, either in the form a.b.c.d or as number of valid top-most bits. Default is 10.0.2.0/24. host=addr Specify the guest-visible address of the host. Default is the 2nd IP in the guest network, i.e. x.x.x.2. ipv6-net=addr[/int] Set IPv6 network address the guest will see (default is fec0::/64). The network prefix is given in the usual hexadec- imal IPv6 address notation. The prefix size is optional, and is given as the number of valid top-most bits (default is 64). ipv6-host=addr Specify the guest-visible IPv6 address of the host. Default is the 2nd IPv6 in the guest network, i.e. xxxx::2. restrict=on|off If this option is enabled, the guest will be isolated, i.e. it will not be able to contact the host and no guest IP pack- ets will be routed over the host to the outside. This option does not affect any explicitly set forwarding rules. hostname=name Specifies the client hostname reported by the built-in DHCP server. dhcpstart=addr Specify the first of the 16 IPs the built-in DHCP server can assign. Default is the 15th to 31st IP in the guest network, i.e. x.x.x.15 to x.x.x.31. dns=addr Specify the guest-visible address of the virtual nameserver. The address must be different from the host address. Default is the 3rd IP in the guest network, i.e. x.x.x.3. ipv6-dns=addr Specify the guest-visible address of the IPv6 virtual name- server. The address must be different from the host address. Default is the 3rd IP in the guest network, i.e. xxxx::3. dnssearch=domain Provides an entry for the domain-search list sent by the built-in DHCP server. More than one domain suffix can be transmitted by specifying this option multiple times. If sup- ported, this will cause the guest to automatically try to ap- pend the given domain suffix(es) in case a domain name can not be resolved. Example: qemu-system-x86_64 -nic user,dnssearch=mgmt.example.org,dnssearch=example.org domainname=domain Specifies the client domain name reported by the built-in DHCP server. tftp=dir When using the user mode network stack, activate a built-in TFTP server. The files in dir will be exposed as the root of a TFTP server. The TFTP client on the guest must be config- ured in binary mode (use the command bin of the Unix TFTP client). The built-in TFTP server is read-only; it does not implement any command for writing files. QEMU will not write to this directory. tftp-server-name=name In BOOTP reply, broadcast name as the "TFTP server name" (RFC2132 option 66). This can be used to advise the guest to load boot files or configurations from a different server than the host address. bootfile=file When using the user mode network stack, broadcast file as the BOOTP filename. In conjunction with tftp, this can be used to network boot a guest from a local directory. Example (using pxelinux): qemu-system-x86_64 -hda linux.img -boot n -device e1000,netdev=n1 \ -netdev user,id=n1,tftp=/path/to/tftp/files,bootfile=/pxelinux.0 smb=dir[,smbserver=addr] When using the user mode network stack, activate a built-in SMB server so that Windows OSes can access to the host files in dir transparently. The IP address of the SMB server can be set to addr. By default the 4th IP in the guest network is used, i.e. x.x.x.4. In the guest Windows OS, the line: 10.0.2.4 smbserver must be added in the file C:\WINDOWS\LMHOSTS (for windows 9x/Me) or C:\WINNT\SYSTEM32\DRIVERS\ETC\LMHOSTS (Windows NT/2000). Then dir can be accessed in \\smbserver\qemu. Note that a SAMBA server must be installed on the host OS. hostfwd=[tcp|udp|unix]:[[hostaddr]:hostport|hostpath]-[gues- taddr]:guestport Redirect incoming TCP, UDP or UNIX connections to the host port hostport to the guest IP address guestaddr on guest port guestport. If guestaddr is not specified, its value is x.x.x.15 (default first address given by the built-in DHCP server). By specifying hostaddr, the rule can be bound to a specific host interface. If no connection type is set, TCP is used. This option can be given multiple times. For example, to redirect host X11 connection from screen 1 to guest screen 0, use the following: # on the host qemu-system-x86_64 -nic user,hostfwd=tcp:127.0.0.1:6001-:6000 # this host xterm should open in the guest X11 server xterm -display :1 To redirect telnet connections from host port 5555 to telnet port on the guest, use the following: # on the host qemu-system-x86_64 -nic user,hostfwd=tcp::5555-:23 telnet localhost 5555 Then when you use on the host telnet localhost 5555, you con- nect to the guest telnet server. To redirect host unix socket /tmp/vm to guest tcp socket 23 use following: # on the host qemu-system-x86_64 -nic user,hostfwd=unix:/tmp/vm-:23 guestfwd=[tcp]:server:port-dev; guestfwd=[tcp]:server:port-cmd:com- mand Forward guest TCP connections to the IP address server on port port to the character device dev or to a program exe- cuted by cmd:command which gets spawned for each connection. This option can be given multiple times. You can either use a chardev directly and have that one used throughout QEMU's lifetime, like in the following example: # open 10.10.1.1:4321 on bootup, connect 10.0.2.100:1234 to it whenever # the guest accesses it qemu-system-x86_64 -nic user,guestfwd=tcp:10.0.2.100:1234-tcp:10.10.1.1:4321 Or you can execute a command on every TCP connection estab- lished by the guest, so that QEMU behaves similar to an inetd process for that virtual server: # call "netcat 10.10.1.1 4321" on every TCP connection to 10.0.2.100:1234 # and connect the TCP stream to its stdin/stdout qemu-system-x86_64 -nic 'user,id=n1,guestfwd=tcp:10.0.2.100:1234-cmd:netcat 10.10.1.1 4321' -netdev tap,id=id[,fd=h][,ifname=name][,script=file][,down- script=dfile][,br=bridge][,helper=helper] Configure a host TAP network backend with ID id. Use the network script file to configure it and the network script dfile to deconfigure it. If name is not provided, the OS automati- cally provides one. The default network configure script is /etc/qemu-ifup and the default network deconfigure script is /etc/qemu-ifdown. Use script=no or downscript=no to disable script execution. If running QEMU as an unprivileged user, use the network helper to configure the TAP interface and attach it to the bridge. The de- fault network helper executable is /path/to/qemu-bridge-helper and the default bridge device is br0. fd=h can be used to specify the handle of an already opened host TAP interface. Examples: #launch a QEMU instance with the default network script qemu-system-x86_64 linux.img -nic tap #launch a QEMU instance with two NICs, each one connected #to a TAP device qemu-system-x86_64 linux.img \ -netdev tap,id=nd0,ifname=tap0 -device e1000,netdev=nd0 \ -netdev tap,id=nd1,ifname=tap1 -device rtl8139,netdev=nd1 #launch a QEMU instance with the default network helper to #connect a TAP device to bridge br0 qemu-system-x86_64 linux.img -device virtio-net-pci,netdev=n1 \ -netdev tap,id=n1,"helper=/path/to/qemu-bridge-helper" -netdev bridge,id=id[,br=bridge][,helper=helper] Connect a host TAP network interface to a host bridge device. Use the network helper helper to configure the TAP interface and at- tach it to the bridge. The default network helper executable is /path/to/qemu-bridge-helper and the default bridge device is br0. Examples: #launch a QEMU instance with the default network helper to #connect a TAP device to bridge br0 qemu-system-x86_64 linux.img -netdev bridge,id=n1 -device virtio-net,netdev=n1 #launch a QEMU instance with the default network helper to #connect a TAP device to bridge qemubr0 qemu-system-x86_64 linux.img -netdev bridge,br=qemubr0,id=n1 -device virtio-net,netdev=n1 -netdev socket,id=id[,fd=h][,listen=[host]:port][,connect=host:port] This host network backend can be used to connect the guest's network to another QEMU virtual machine using a TCP socket connection. If listen is specified, QEMU waits for incoming connections on port (host is optional). connect is used to connect to another QEMU in- stance using the listen option. fd=h specifies an already opened TCP socket. Example: # launch a first QEMU instance qemu-system-x86_64 linux.img \ -device e1000,netdev=n1,mac=52:54:00:12:34:56 \ -netdev socket,id=n1,listen=:1234 # connect the network of this instance to the network of the first instance qemu-system-x86_64 linux.img \ -device e1000,netdev=n2,mac=52:54:00:12:34:57 \ -netdev socket,id=n2,connect=127.0.0.1:1234 -netdev socket,id=id[,fd=h][,mcast=maddr:port[,localaddr=addr]] Configure a socket host network backend to share the guest's network traffic with another QEMU virtual machines using a UDP multicast socket, effectively making a bus for every QEMU with same multicast address maddr and port. NOTES: 1. Several QEMU can be running on different hosts and share same bus (assuming correct multicast setup for these hosts). 2. mcast support is compatible with User Mode Linux (argument ethN=mcast), see http://user-mode-linux.sf.net. 3. Use fd=h to specify an already opened UDP multicast socket. Example: # launch one QEMU instance qemu-system-x86_64 linux.img \ -device e1000,netdev=n1,mac=52:54:00:12:34:56 \ -netdev socket,id=n1,mcast=230.0.0.1:1234 # launch another QEMU instance on same "bus" qemu-system-x86_64 linux.img \ -device e1000,netdev=n2,mac=52:54:00:12:34:57 \ -netdev socket,id=n2,mcast=230.0.0.1:1234 # launch yet another QEMU instance on same "bus" qemu-system-x86_64 linux.img \ -device e1000,netdev=n3,mac=52:54:00:12:34:58 \ -netdev socket,id=n3,mcast=230.0.0.1:1234 Example (User Mode Linux compat.): # launch QEMU instance (note mcast address selected is UML's default) qemu-system-x86_64 linux.img \ -device e1000,netdev=n1,mac=52:54:00:12:34:56 \ -netdev socket,id=n1,mcast=239.192.168.1:1102 # launch UML /path/to/linux ubd0=/path/to/root_fs eth0=mcast Example (send packets from host's 1.2.3.4): qemu-system-x86_64 linux.img \ -device e1000,netdev=n1,mac=52:54:00:12:34:56 \ -netdev socket,id=n1,mcast=239.192.168.1:1102,localaddr=1.2.3.4 -netdev stream,id=str[,server=on|off],addr.type=inet,addr.host=host,addr.port=port[,to=max- port][,nu- meric=on|off][,keep-alive=on|off][,mptcp=on|off][,addr.ipv4=on|off][,addr.ipv6=on|off][,re- connect-ms=milliseconds] Configure a network backend to connect to another QEMU virtual ma- chine or a proxy using a TCP/IP socket. server=on|off if on create a server socket addr.host=host,addr.port=port socket address to listen on (server=on) or connect to (server=off) to=maxport if present, this is range of possible addresses, with port between port and maxport. numeric=on|off if on host and port are guaranteed to be numeric, otherwise a name resolution should be attempted (default: off) keep-alive=on|off enable keep-alive when connecting to this socket. Not sup- ported for passive sockets. mptcp=on|off enable multipath TCP ipv4=on|off whether to accept IPv4 addresses, default to try both IPv4 and IPv6 ipv6=on|off whether to accept IPv6 addresses, default to try both IPv4 and IPv6 reconnect-ms=milliseconds for a client socket, if a socket is disconnected, then at- tempt a reconnect after the given number of milliseconds. Setting this to zero disables this function. (default: 0) Example (two guests connected using a TCP/IP socket): # first VM qemu-system-x86_64 linux.img \ -device virtio-net,netdev=net0,mac=52:54:00:12:34:56 \ -netdev stream,id=net0,server=on,addr.type=inet,addr.host=localhost,addr.port=1234 # second VM qemu-system-x86_64 linux.img \ -device virtio-net,netdev=net0,mac=52:54:00:12:34:57 \ -netdev stream,id=net0,server=off,addr.type=inet,addr.host=localhost,addr.port=1234,reconnect-ms=5000 -netdev stream,id=str[,server=on|off],addr.type=unix,addr.path=path[,ab- stract=on|off][,tight=on|off][,reconnect-ms=milliseconds] Configure a network backend to connect to another QEMU virtual ma- chine or a proxy using a stream oriented unix domain socket. server=on|off if on create a server socket addr.path=path filesystem path to use abstract=on|off if on, this is a Linux abstract socket address. tight=on|off if false, pad an abstract socket address with enough null bytes to make it fill struct sockaddr_un member sun_path. reconnect-ms=milliseconds for a client socket, if a socket is disconnected, then at- tempt a reconnect after the given number of milliseconds. Setting this to zero disables this function. (default: 0) Example (using passt as a replacement of -netdev user): # start passt server as a non privileged user passt UNIX domain socket bound at /tmp/passt_1.socket # start QEMU to connect to passt qemu-system-x86_64 linux.img \ -device virtio-net,netdev=net0 \ -netdev stream,id=net0,server=off,addr.type=unix,addr.path=/tmp/passt_1.socket Example (two guests connected using a stream oriented unix domain socket): # first VM qemu-system-x86_64 linux.img \ -device virtio-net,netdev=net0,mac=52:54:00:12:34:56 \ netdev stream,id=net0,server=on,addr.type=unix,addr.path=/tmp/qemu0 # second VM qemu-system-x86_64 linux.img \ -device virtio-net,netdev=net0,mac=52:54:00:12:34:57 \ -netdev stream,id=net0,server=off,addr.type=unix,addr.path=/tmp/qemu0,reconnect-ms=5000 -netdev stream,id=str[,server=on|off],addr.type=fd,addr.str=file-descrip- tor[,reconnect-ms=milliseconds] Configure a network backend to connect to another QEMU virtual ma- chine or a proxy using a stream oriented socket file descriptor. server=on|off if on create a server socket addr.str=file-descriptor file descriptor number to use as a socket reconnect-ms=milliseconds for a client socket, if a socket is disconnected, then at- tempt a reconnect after the given number of milliseconds. Setting this to zero disables this function. (default: 0) -netdev dgram,id=str,remote.type=inet,remote.host=maddr,re- mote.port=port[,local.type=inet,local.host=addr] Configure a network backend to connect to a multicast address. remote.host=maddr,remote.port=port multicast address local.host=addr specify the host address to send packets from Example: # launch one QEMU instance qemu-system-x86_64 linux.img \ -device virtio-net,netdev=net0,mac=52:54:00:12:34:56 \ -netdev dgram,id=net0,remote.type=inet,remote.host=224.0.0.1,remote.port=1234 # launch another QEMU instance on same "bus" qemu-system-x86_64 linux.img \ -device virtio-net,netdev=net0,mac=52:54:00:12:34:57 \ -netdev dgram,id=net0,remote.type=inet,remote.host=224.0.0.1,remote.port=1234 # launch yet another QEMU instance on same "bus" qemu-system-x86_64 linux.img \ -device virtio-net,netdev=net0,mac=52:54:00:12:34:58 \ -netdev dgram,id=net0,remote.type=inet,remote.host=224.0.0.1,remote.port=1234 -netdev dgram,id=str,remote.type=inet,remote.host=maddr,re- mote.port=port[,local.type=fd,local.str=file-descriptor] Configure a network backend to connect to a multicast address using a UDP socket file descriptor. remote.host=maddr,remote.port=port multicast address local.str=file-descriptor File descriptor to use to send packets -netdev dgram,id=str,local.type=inet,local.host=addr,local.port=port[,re- mote.type=inet,remote.host=addr,remote.port=port] Configure a network backend to connect to another QEMU virtual ma- chine or a proxy using a datagram oriented unix domain socket. local.host=addr,local.port=port IP address to use to send the packets from remote.host=addr,remote.port=port Destination IP address Example (two guests connected using an UDP/IP socket): # first VM qemu-system-x86_64 linux.img \ -device virtio-net,netdev=net0,mac=52:54:00:12:34:56 \ -netdev dgram,id=net0,local.type=inet,local.host=localhost,local.port=1234,remote.type=inet,remote.host=localhost,remote.port=1235 # second VM qemu-system-x86_64 linux.img \ -device virtio-net,netdev=net0,mac=52:54:00:12:34:56 \ -netdev dgram,id=net0,local.type=inet,local.host=localhost,local.port=1235,remote.type=inet,remote.host=localhost,remote.port=1234 -netdev dgram,id=str,local.type=unix,local.path=path[,remote.type=unix,re- mote.path=path] Configure a network backend to connect to another QEMU virtual ma- chine or a proxy using a datagram oriented unix socket. local.path=path filesystem path to use to bind the socket remote.path=path filesystem path to use as a destination (see sendto(2)) Example (two guests connected using an UDP/UNIX socket): # first VM qemu-system-x86_64 linux.img \ -device virtio-net,netdev=net0,mac=52:54:00:12:34:56 \ -netdev dgram,id=net0,local.type=unix,local.path=/tmp/qemu0,remote.type=unix,remote.path=/tmp/qemu1 # second VM qemu-system-x86_64 linux.img \ -device virtio-net,netdev=net0,mac=52:54:00:12:34:57 \ -netdev dgram,id=net0,local.type=unix,local.path=/tmp/qemu1,remote.type=unix,remote.path=/tmp/qemu0 -netdev dgram,id=str,local.type=fd,local.str=file-descriptor Configure a network backend to connect to another QEMU virtual ma- chine or a proxy using a datagram oriented socket file descriptor. local.str=file-descriptor File descriptor to use to send packets -netdev l2tpv3,id=id,src=srcaddr,dst=dstaddr[,srcport=srcport][,dst- port=dstport],txsession=txsession[,rxsession=rxses- sion][,ipv6=on|off][,udp=on|off][,cookie64=on|off][,counter=on|off][,pin- counter=on|off][,txcookie=txcookie][,rxcookie=rxcookie][,offset=offset] Configure a L2TPv3 pseudowire host network backend. L2TPv3 (RFC3931) is a popular protocol to transport Ethernet (and other Layer 2) data frames between two systems. It is present in routers, firewalls and the Linux kernel (from version 3.3 onwards). This transport allows a VM to communicate to another VM, router or firewall directly. src=srcaddr source address (mandatory) dst=dstaddr destination address (mandatory) udp=on select udp encapsulation (default is ip). srcport=srcport source udp port. dstport=dstport destination udp port. ipv6=on force v6, otherwise defaults to v4. rxcookie=rxcookie; txcookie=txcookie Cookies are a weak form of security in the l2tpv3 specifica- tion. Their function is mostly to prevent misconfiguration. By default they are 32 bit. cookie64=on Set cookie size to 64 bit instead of the default 32 counter=off Force a 'cut-down' L2TPv3 with no counter as in draft-mkon- stan-l2tpext-keyed-ipv6-tunnel-00 pincounter=on Work around broken counter handling in peer. This may also help on networks which have packet reorder. offset=offset Add an extra offset between header and data For example, to attach a VM running on host 4.3.2.1 via L2TPv3 to the bridge br-lan on the remote Linux host 1.2.3.4: # Setup tunnel on linux host using raw ip as encapsulation # on 1.2.3.4 ip l2tp add tunnel remote 4.3.2.1 local 1.2.3.4 tunnel_id 1 peer_tunnel_id 1 \ encap udp udp_sport 16384 udp_dport 16384 ip l2tp add session tunnel_id 1 name vmtunnel0 session_id \ 0xFFFFFFFF peer_session_id 0xFFFFFFFF ifconfig vmtunnel0 mtu 1500 ifconfig vmtunnel0 up brctl addif br-lan vmtunnel0 # on 4.3.2.1 # launch QEMU instance - if your network has reorder or is very lossy add ,pincounter qemu-system-x86_64 linux.img -device e1000,netdev=n1 \ -netdev l2tpv3,id=n1,src=4.2.3.1,dst=1.2.3.4,udp=on,srcport=16384,dstport=16384,rxsession=0xffffffff,txsession=0xffffffff,counter=on -netdev vde,id=id[,sock=socketpath][,port=n][,group=groupname][,mode=oc- talmode] Configure VDE backend to connect to PORT n of a vde switch running on host and listening for incoming connections on socketpath. Use GROUP groupname and MODE octalmode to change default ownership and permissions for communication port. This option is only available if QEMU has been compiled with vde support enabled. Example: # launch vde switch vde_switch -F -sock /tmp/myswitch # launch QEMU instance qemu-system-x86_64 linux.img -nic vde,sock=/tmp/myswitch -netdev af-xdp,id=str,ifname=name[,mode=na- tive|skb][,force-copy=on|off][,queues=n][,start-queue=m][,in- hibit=on|off][,sock-fds=x:y:...:z][,map-path=/path/to/socket/map][,map-start-in- dex=i] Configure AF_XDP backend to connect to a network interface 'name' using AF_XDP socket. A specific program attach mode for a default XDP program can be forced with 'mode', defaults to best-effort, where the likely most performant mode will be in use. Number of queues 'n' should generally match the number or queues in the inter- face, defaults to 1. Traffic arriving on non-configured device queues will not be delivered to the network backend. # set number of queues to 4 ethtool -L eth0 combined 4 # launch QEMU instance qemu-system-x86_64 linux.img -device virtio-net-pci,netdev=n1 \ -netdev af-xdp,id=n1,ifname=eth0,queues=4 'start-queue' option can be specified if a particular range of queues [m, m + n] should be in use. For example, this is may be necessary in order to use certain NICs in native mode. Kernel al- lows the driver to create a separate set of XDP queues on top of regular ones, and only these queues can be used for AF_XDP sockets. NICs that work this way may also require an additional traffic redi- rection with ethtool to these special queues. # set number of queues to 1 ethtool -L eth0 combined 1 # redirect all the traffic to the second queue (id: 1) # note: drivers may require non-empty key/mask pair. ethtool -N eth0 flow-type ether \ dst 00:00:00:00:00:00 m FF:FF:FF:FF:FF:FE action 1 ethtool -N eth0 flow-type ether \ dst 00:00:00:00:00:01 m FF:FF:FF:FF:FF:FE action 1 # launch QEMU instance qemu-system-x86_64 linux.img -device virtio-net-pci,netdev=n1 \ -netdev af-xdp,id=n1,ifname=eth0,queues=1,start-queue=1 XDP program can also be loaded externally. In this case 'inhibit' option should be set to 'on'. Either 'sock-fds' or 'map-path' can be used with 'inhibit' enabled. 'sock-fds' can be provided with file descriptors for already open but not bound XDP sockets already added to a socket map for corresponding queues. One socket per queue. qemu-system-x86_64 linux.img -device virtio-net-pci,netdev=n1 \ -netdev af-xdp,id=n1,ifname=eth0,queues=3,inhibit=on,sock-fds=15:16:17 For the 'inhibit' option set to 'on' used together with 'map-path' it is expected that the XDP program with the socket map is already loaded on the networking device and the map pinned into BPF file system. The path to the pinned map is then passed to QEMU which then creates the file descriptors and inserts them into the existing socket map. qemu-system-x86_64 linux.img -device virtio-net-pci,netdev=n1 \ -netdev af-xdp,id=n1,ifname=eth0,queues=2,inhibit=on,map-path=/sys/fs/bpf/xsks_map Additionally, 'map-start-index' can be used to specify the start offset for insertion into the socket map. The combination of 'map-path' and 'sock-fds' together is not supported. -netdev vhost-user,chardev=id[,vhostforce=on|off][,queues=n] Establish a vhost-user netdev, backed by a chardev id. The chardev should be a unix domain socket backed one. The vhost-user uses a specifically defined protocol to pass vhost ioctl replacement mes- sages to an application on the other end of the socket. On non-MSIX guests, the feature can be forced with vhostforce. Use 'queues=n' to specify the number of queues to be created for multiqueue vhost-user. Example: qemu -m 512 -object memory-backend-file,id=mem,size=512M,mem-path=/hugetlbfs,share=on \ -numa node,memdev=mem \ -chardev socket,id=chr0,path=/path/to/socket \ -netdev type=vhost-user,id=net0,chardev=chr0 \ -device virtio-net-pci,netdev=net0 -netdev vhost-vdpa[,vhostdev=/path/to/dev][,vhostfd=h] Establish a vhost-vdpa netdev. vDPA device is a device that uses a datapath which complies with the virtio specifications with a vendor specific control path. vDPA de- vices can be both physically located on the hardware or emulated by software. -netdev hubport,id=id,hubid=hubid[,netdev=nd] Create a hub port on the emulated hub with ID hubid. The hubport netdev lets you connect a NIC to a QEMU emulated hub in- stead of a single netdev. Alternatively, you can also connect the hubport to another netdev with ID nd by using the netdev=nd option. -net nic[,netdev=nd][,macaddr=mac][,model=type] [,name=name][,addr=addr][,vectors=v] Legacy option to configure or create an on-board (or machine de- fault) Network Interface Card(NIC) and connect it either to the emu- lated hub with ID 0 (i.e. the default hub), or to the netdev nd. If model is omitted, then the default NIC model associated with the ma- chine type is used. Note that the default NIC model may change in future QEMU releases, so it is highly recommended to always specify a model. Optionally, the MAC address can be changed to mac, the de- vice address set to addr (PCI cards only), and a name can be as- signed for use in monitor commands. Optionally, for PCI cards, you can specify the number v of MSI-X vectors that the card should have; this option currently only affects virtio cards; set v = 0 to dis- able MSI-X. If no -net option is specified, a single NIC is created. QEMU can emulate several different models of network card. Use -net nic,model=help for a list of available devices for your target. -net user|passt|tap|bridge|socket|l2tpv3|vde[,...][,name=name] Configure a host network backend (with the options corresponding to the same -netdev option) and connect it to the emulated hub 0 (the default hub). Use name to specify the name of the hub port. Character device options The general form of a character device option is: -chardev backend,id=id[,mux=on|off][,options] Backend is one of: null, socket, udp, msmouse, hub, vc, ringbuf, file, pipe, console, serial, pty, stdio, braille, parallel, spicevmc, spiceport. The specific backend will determine the applic- able options. Use -chardev help to print all available chardev backend types. All devices must have an id, which can be any string up to 127 char- acters long. It is used to uniquely identify this device in other command line directives. A character device may be used in multiplexing mode by multiple front-ends. Specify mux=on to enable this mode. A multiplexer is a "1:N" device, and here the "1" end is your specified chardev back- end, and the "N" end is the various parts of QEMU that can talk to a chardev. If you create a chardev with id=myid and mux=on, QEMU will create a multiplexer with your specified ID, and you can then con- figure multiple front ends to use that chardev ID for their in- put/output. Up to four different front ends can be connected to a single multiplexed chardev. (Without multiplexing enabled, a chardev can only be used by a single front end.) For instance you could use this to allow a single stdio chardev to be used by two serial ports and the QEMU monitor: -chardev stdio,mux=on,id=char0 \ -mon chardev=char0,mode=readline \ -serial chardev:char0 \ -serial chardev:char0 You can have more than one multiplexer in a system configuration; for instance you could have a TCP port multiplexed between UART 0 and UART 1, and stdio multiplexed between the QEMU monitor and a parallel port: -chardev stdio,mux=on,id=char0 \ -mon chardev=char0,mode=readline \ -parallel chardev:char0 \ -chardev tcp,...,mux=on,id=char1 \ -serial chardev:char1 \ -serial chardev:char1 When you're using a multiplexed character device, some escape se- quences are interpreted in the input. See the chapter about Keys in the character backend multiplexer in the System Emulation Users Guide for more details. Note that some other command line options may implicitly create mul- tiplexed character backends; for instance -serial mon:stdio creates a multiplexed stdio backend connected to the serial port and the QEMU monitor, and -nographic also multiplexes the console and the monitor to stdio. If you need to aggregate data in the opposite direction (where one QEMU frontend interface receives input and output from multiple backend chardev devices), please refer to the paragraph below re- garding chardev hub aggregator device configuration. Every backend supports the logfile option, which supplies the path to a file to record all data transmitted via the backend. The logap- pend option controls whether the log file will be truncated or ap- pended to when opened. The available backends are: -chardev null,id=id A void device. This device will not emit any data, and will drop any data it receives. The null backend does not take any options. -chardev socket,id=id[,TCP options or unix op- tions][,server=on|off][,wait=on|off][,telnet=on|off][,web- socket=on|off][,reconnect-ms=milliseconds][,tls-creds=id][,tls-authz=id] Create a two-way stream socket, which can be either a TCP or a unix socket. A unix socket will be created if path is specified. Behav- iour is undefined if TCP options are specified for a unix socket. server=on|off specifies that the socket shall be a listening socket. wait=on|off specifies that QEMU should not block waiting for a client to connect to a listening socket. telnet=on|off specifies that traffic on the socket should interpret telnet escape sequences. websocket=on|off specifies that the socket uses WebSocket protocol for communication. reconnect-ms sets the timeout for reconnecting on non-server sockets when the remote end goes away. qemu will delay this many millisec- onds and then attempt to reconnect. Zero disables reconnecting, and is the default. tls-creds requests enablement of the TLS protocol for encryption, and specifies the id of the TLS credentials to use for the hand- shake. The credentials must be previously created with the -object tls-creds argument. tls-auth provides the ID of the QAuthZ authorization object against which the client's x509 distinguished name will be validated. This object is only resolved at time of use, so can be deleted and recre- ated on the fly while the chardev server is active. If missing, it will default to denying access. TCP and unix socket options are given below: TCP options: port=port[,host=host][,to=to][,ipv4=on|off][,ipv6=on|off][,node- lay=on|off] host for a listening socket specifies the local address to be bound. For a connecting socket species the remote host to connect to. host is optional for listening sockets. If not specified it defaults to 0.0.0.0. port for a listening socket specifies the local port to be bound. For a connecting socket specifies the port on the re- mote host to connect to. port can be given as either a port number or a service name. port is required. to is only relevant to listening sockets. If it is specified, and port cannot be bound, QEMU will attempt to bind to subse- quent ports up to and including to until it succeeds. to must be specified as a port number. ipv4=on|off and ipv6=on|off specify that either IPv4 or IPv6 must be used. If neither is specified the socket may use ei- ther protocol. nodelay=on|off disables the Nagle algorithm. unix options: path=path[,abstract=on|off][,tight=on|off] path specifies the local path of the unix socket. path is re- quired. abstract=on|off specifies the use of the abstract socket namespace, rather than the filesystem. Optional, de- faults to false. tight=on|off sets the socket length of ab- stract sockets to their minimum, rather than the full sun_path length. Optional, defaults to true. -chardev udp,id=id[,host=host],port=port[,localaddr=localaddr][,local- port=localport][,ipv4=on|off][,ipv6=on|off] Sends all traffic from the guest to a remote host over UDP. host specifies the remote host to connect to. If not specified it defaults to localhost. port specifies the port on the remote host to connect to. port is required. localaddr specifies the local address to bind to. If not specified it defaults to 0.0.0.0. localport specifies the local port to bind to. If not specified any available local port will be used. ipv4=on|off and ipv6=on|off specify that either IPv4 or IPv6 must be used. If neither is specified the device may use either protocol. -chardev msmouse,id=id Forward QEMU's emulated msmouse events to the guest. msmouse does not take any options. -chardev hub,id=id,chardevs.0=id[,chardevs.N=id] Explicitly create chardev backend hub device with the possibility to aggregate input from multiple backend devices and forward it to a single frontend device. Additionally, hub device takes the output from the frontend device and sends it back to all the connected backend devices. This allows for seamless interaction between dif- ferent backend devices and a single frontend interface. Aggregation supported for up to 4 chardev devices. (Since 10.0) For example, the following is a use case of 2 backend devices: vir- tual console vc0 and a pseudo TTY pty0 connected to a single virtio hvc console frontend device with a hub hub0 help. Virtual console renders text to an image, which can be shared over the VNC protocol. In turn, pty backend provides bidirectional communication to the virtio hvc console over the pseudo TTY file. The example configura- tion can be as follows: -chardev pty,path=/tmp/pty,id=pty0 \ -chardev vc,id=vc0 \ -chardev hub,id=hub0,chardevs.0=pty0,chardevs.1=vc0 \ -device virtconsole,chardev=hub0 \ -vnc 0.0.0.0:0 Once QEMU starts VNC client and any TTY emulator can be used to con- trol a single hvc console: # Start TTY emulator tio /tmp/pty # Start VNC client and switch to virtual console Ctrl-Alt-2 vncviewer :0 Several frontend devices is not supported. Stacking of multiplexers and hub devices is not supported as well. -chardev vc,id=id[[,width=width][,height=height]][[,cols=cols][,rows=rows]] Connect to a QEMU text console. vc may optionally be given a spe- cific size. width and height specify the width and height respectively of the console, in pixels. cols and rows specify that the console be sized to fit a text con- sole with the given dimensions. -chardev ringbuf,id=id[,size=size] Create a ring buffer with fixed size size. size must be a power of two and defaults to 64K. -chardev file,id=id,path=path[,input-path=input-path] Log all traffic received from the guest to a file. path specifies the path of the file to be opened. This file will be created if it does not already exist, and overwritten if it does. path is required. If input-path is specified, this is the path of a second file which will be used for input. If input-path is not specified, no input will be available from the chardev. Note that input-path is not supported on Windows hosts. -chardev pipe,id=id,path=path Create a two-way connection to the guest. The behaviour differs slightly between Windows hosts and other hosts: On Windows, a single duplex pipe will be created at \\.pipe\path. On other hosts, 2 pipes will be created called path.in and path.out. Data written to path.in will be received by the guest. Data written by the guest can be read from path.out. QEMU will not create these fifos, and requires them to be present. path forms part of the pipe path as described above. path is re- quired. -chardev console,id=id Send traffic from the guest to QEMU's standard output. console does not take any options. console is only available on Windows hosts. -chardev serial,id=id,path=path Send traffic from the guest to a serial device on the host. On Unix hosts serial will actually accept any tty device, not only serial lines. path specifies the name of the serial device to open. -chardev pty,id=id[,path=path] Create a new pseudo-terminal on the host and connect to it. pty is not available on Windows hosts. If path is specified, QEMU will create a symbolic link at that loca- tion which points to the new PTY device. This avoids having to make QMP or HMP monitor queries to find out what the new PTY device path is. Note that while QEMU will remove the symlink when it exits grace- fully, it will not do so in case of crashes or on certain startup errors. It is recommended that the user checks and removes the sym- link after QEMU terminates to account for this. -chardev stdio,id=id[,signal=on|off] Connect to standard input and standard output of the QEMU process. signal controls if signals are enabled on the terminal, that in- cludes exiting QEMU with the key sequence Control-c. This option is enabled by default, use signal=off to disable it. -chardev braille,id=id Connect to a local BrlAPI server. braille does not take any options. -chardev parallel,id=id,path=path parallel is only available on Linux, FreeBSD and DragonFlyBSD hosts. Connect to a local parallel port. path specifies the path to the parallel port device. path is required. -chardev spicevmc,id=id,debug=debug,name=name spicevmc is only available when spice support is built in. debug debug level for spicevmc name name of spice channel to connect to Connect to a spice virtual machine channel, such as vdiport. -chardev spiceport,id=id,debug=debug,name=name spiceport is only available when spice support is built in. debug debug level for spicevmc name name of spice port to connect to Connect to a spice port, allowing a Spice client to handle the traf- fic identified by a name (preferably a fqdn). TPM device options The general form of a TPM device option is: -tpmdev backend,id=id[,options] The specific backend type will determine the applicable options. The -tpmdev option creates the TPM backend and requires a -device option that specifies the TPM frontend interface model. Use -tpmdev help to print all available TPM backend types. The available backends are: -tpmdev passthrough,id=id,path=path,cancel-path=cancel-path (Linux-host only) Enable access to the host's TPM using the passthrough driver. path specifies the path to the host's TPM device, i.e., on a Linux host this would be /dev/tpm0. path is optional and by default /dev/tpm0 is used. cancel-path specifies the path to the host TPM device's sysfs entry allowing for cancellation of an ongoing TPM command. cancel-path is optional and by default QEMU will search for the sysfs entry to use. Some notes about using the host's TPM with the passthrough driver: The TPM device accessed by the passthrough driver must not be used by any other application on the host. Since the host's firmware (BIOS/UEFI) has already initialized the TPM, the VM's firmware (BIOS/UEFI) will not be able to initialize the TPM again and may therefore not show a TPM-specific menu that would otherwise allow the user to configure the TPM, e.g., allow the user to enable/disable or activate/deactivate the TPM. Further, if TPM ownership is released from within a VM then the host's TPM will get disabled and deactivated. To enable and activate the TPM again afterwards, the host has to be rebooted and the user is required to enter the firmware's menu to enable and activate the TPM. If the TPM is left disabled and/or deactivated most TPM commands will fail. To create a passthrough TPM use the following two options: -tpmdev passthrough,id=tpm0 -device tpm-tis,tpmdev=tpm0 Note that the -tpmdev id is tpm0 and is referenced by tpmdev=tpm0 in the device option. -tpmdev emulator,id=id,chardev=dev (Linux-host only) Enable access to a TPM emulator using Unix domain socket based chardev backend. chardev specifies the unique ID of a character device backend that provides connection to the software TPM server. To create a TPM emulator backend device with chardev socket backend: -chardev socket,id=chrtpm,path=/tmp/swtpm-sock -tpmdev emulator,id=tpm0,chardev=chrtpm -device tpm-tis,tpmdev=tpm0 Boot Image or Kernel specific There are broadly 4 ways you can boot a system with QEMU. * specify a firmware and let it control finding a kernel * specify a firmware and pass a hint to the kernel to boot * direct kernel image boot * manually load files into the guest's address space The third method is useful for quickly testing kernels but as there is no firmware to pass configuration information to the kernel the hardware must either be probeable, the kernel built for the exact configuration or passed some configuration data (e.g. a DTB blob) which tells the kernel what dri- vers it needs. This exact details are often hardware specific. The final method is the most generic way of loading images into the guest address space and used mostly for bare metal type development where the re- set vectors of the processor are taken into account. For x86 machines and some other architectures -bios will generally do the right thing with whatever it is given. For other machines the more strict -pflash option needs an image that is sized for the flash device for the given machine type. Please see the QEMU System Emulator Targets section of the manual for more detailed documentation. -bios file Set the filename for the BIOS. -pflash file Use file as a parallel flash image. The kernel options were designed to work with Linux kernels although other things (like hypervisors) can be packaged up as a kernel executable image. The exact format of a executable image is usually architecture specific. The way in which the kernel is started (what address it is loaded at, what if any information is passed to it via CPU registers, the state of the hardware when it is started, and so on) is also architecture specific. Typ- ically it follows the specification laid down by the Linux kernel for how kernels for that architecture must be started. -kernel bzImage Use bzImage as kernel image. The kernel can be either a Linux kernel or in multiboot format. -shim shim.efi Use 'shim.efi' to boot the kernel -append cmdline Use cmdline as kernel command line -initrd file Use file as initial ram disk. -initrd "file1 arg=foo,file2" This syntax is only available with multiboot. Use file1 and file2 as modules and pass arg=foo as parameter to the first module. Commas can be provided in module parameters by dou- bling them on the command line to escape them: -initrd "bzImage earlyprintk=xen,,keep root=/dev/xvda1,initrd.img" Multiboot only. Use bzImage as the first module with "ear- lyprintk=xen,keep root=/dev/xvda1" as its command line, and ini- trd.img as the second module. -dtb file Use file as a device tree binary (dtb) image and pass it to the ker- nel on boot. Finally you can also manually load images directly into the address space of the guest. This is most useful for developers who already know the lay- out of their guest and take care to ensure something sane will happen when the reset vector executes. The generic loader can be invoked by using the loader device: -device loader,addr=<addr>,data=<data>,data-len=<data-len>[,data-be=<data-be>][,cpu-num=<cpu-num>] there is also the guest loader which operates in a similar way but tweaks the DTB so a hypervisor loaded via -kernel can find where the guest image is: -device guest-loader,addr=<addr>[,kernel=<path>,[bootargs=<argu- ments>]][,initrd=<path>] Debug/Expert options -compat [deprecated-input=<input-policy>][,deprecated-output=<output-pol- icy>] Set policy for handling deprecated management interfaces (experimen- tal): deprecated-input=accept (default) Accept deprecated commands and arguments deprecated-input=reject Reject deprecated commands and arguments deprecated-input=crash Crash on deprecated commands and arguments deprecated-output=accept (default) Emit deprecated command results and events deprecated-output=hide Suppress deprecated command results and events Limitation: covers only syntactic aspects of QMP. -compat [unstable-input=<input-policy>][,unstable-output=<output-policy>] Set policy for handling unstable management interfaces (experimen- tal): unstable-input=accept (default) Accept unstable commands and arguments unstable-input=reject Reject unstable commands and arguments unstable-input=crash Crash on unstable commands and arguments unstable-output=accept (default) Emit unstable command results and events unstable-output=hide Suppress unstable command results and events Limitation: covers only syntactic aspects of QMP. -fw_cfg [name=]name,file=file Add named fw_cfg entry with contents from file file. If the file- name contains comma, you must double it (for instance, "file=my,,file" to use file "my,file"). -fw_cfg [name=]name,string=str Add named fw_cfg entry with contents from string str. If the string contains comma, you must double it (for instance, "string=my,,string" to use file "my,string"). The terminating NUL character of the contents of str will not be in- cluded as part of the fw_cfg item data. To insert contents with em- bedded NUL characters, you have to use the file parameter. The fw_cfg entries are passed by QEMU through to the guest. Example: -fw_cfg name=opt/com.mycompany/blob,file=./my_blob.bin creates an fw_cfg entry named opt/com.mycompany/blob with contents from ./my_blob.bin. -serial dev Redirect the virtual serial port to host character device dev. The default device is vc in graphical mode and stdio in non graphical mode. This option can be used several times to simulate multiple serial ports. You can use -serial none to suppress the creation of default serial devices. Available character devices are: vc[:WxH] Virtual console. Optionally, a width and height can be given in pixel with vc:800x600 It is also possible to specify width or height in characters: vc:80Cx24C pty[:path] [Linux only] Pseudo TTY (a new PTY is automatically allo- cated). If path is specified, QEMU will create a symbolic link at that location which points to the new PTY device. This avoids having to make QMP or HMP monitor queries to find out what the new PTY device path is. Note that while QEMU will remove the symlink when it exits gracefully, it will not do so in case of crashes or on cer- tain startup errors. It is recommended that the user checks and removes the symlink after QEMU terminates to account for this. none No device is allocated. Note that for machine types which em- ulate systems where a serial device is always present in real hardware, this may be equivalent to the null option, in that the serial device is still present but all output is dis- carded. For boards where the number of serial ports is truly variable, this suppresses the creation of the device. null A guest will see the UART or serial device as present in the machine, but all output is discarded, and there is no input. Conceptually equivalent to redirecting the output to /dev/null. chardev:id Use a named character device defined with the -chardev op- tion. /dev/XXX [Linux only] Use host tty, e.g. /dev/ttyS0. The host serial port parameters are set according to the emulated ones. /dev/parportN [Linux only, parallel port only] Use host parallel port N. Currently SPP and EPP parallel port features can be used. file:filename Write output to filename. No character can be read. stdio [Unix only] standard input/output pipe:filename name pipe filename COMn [Windows only] Use host serial port n udp:[remote_host]:remote_port[@[src_ip]:src_port] This implements UDP Net Console. When remote_host or src_ip are not specified they default to 0.0.0.0. When not using a specified src_port a random port is automatically chosen. If you just want a simple readonly console you can use netcat or nc, by starting QEMU with: -serial udp::4555 and nc as: nc -u -l -p 4555. Any time QEMU writes something to that port it will appear in the netconsole session. If you plan to send characters back via netconsole or you want to stop and start QEMU a lot of times, you should have QEMU use the same source port each time by using something like -serial udp::4555@:4556 to QEMU. Another approach is to use a patched version of netcat which can listen to a TCP port and send and receive characters via udp. If you have a patched version of netcat which activates telnet remote echo and single char transfer, then you can use the following op- tions to set up a netcat redirector to allow telnet on port 5555 to access the QEMU port. QEMU Options: -serial udp::4555@:4556 netcat options: -u -P 4555 -L 0.0.0.0:4556 -t -p 5555 -I -T telnet options: localhost 5555 tcp:[host]:port[,server=on|off][,wait=on|off][,nodelay=on|off][,re- connect-ms=milliseconds] The TCP Net Console has two modes of operation. It can send the serial I/O to a location or wait for a connection from a location. By default the TCP Net Console is sent to host at the port. If you use the server=on option QEMU will wait for a client socket application to connect to the port before continuing, unless the wait=on|off option was specified. The nodelay=on|off option disables the Nagle buffering algorithm. The reconnect-ms option only applies if server=no is set, if the connection goes down it will attempt to reconnect at the given interval. If host is omitted, 0.0.0.0 is assumed. Only one TCP connection at a time is accepted. You can use tel- net=on to connect to the corresponding character device. Example to send tcp console to 192.168.0.2 port 4444 -serial tcp:192.168.0.2:4444 Example to listen and wait on port 4444 for connection -serial tcp::4444,server=on Example to not wait and listen on ip 192.168.0.100 port 4444 -serial tcp:192.168.0.100:4444,server=on,wait=off telnet:host:port[,server=on|off][,wait=on|off][,nodelay=on|off] The telnet protocol is used instead of raw tcp sockets. The options work the same as if you had specified -serial tcp. The difference is that the port acts like a telnet server or client using telnet option negotiation. This will also allow you to send the MAGIC_SYSRQ sequence if you use a telnet that supports sending the break sequence. Typically in unix telnet you do it with Control-] and then type "send break" followed by pressing the enter key. websocket:host:port,server=on[,wait=on|off][,nodelay=on|off] The WebSocket protocol is used instead of raw tcp socket. The port acts as a WebSocket server. Client mode is not sup- ported. unix:path[,server=on|off][,wait=on|off][,reconnect-ms=milliseconds] A unix domain socket is used instead of a tcp socket. The op- tion works the same as if you had specified -serial tcp ex- cept the unix domain socket path is used for connections. mon:dev_string This is a special option to allow the monitor to be multi- plexed onto another serial port. The monitor is accessed with key sequence of Control-a and then pressing c. dev_string should be any one of the serial devices specified above. An example to multiplex the monitor onto a telnet server listen- ing on port 4444 would be: -serial mon:telnet::4444,server=on,wait=off When the monitor is multiplexed to stdio in this way, Ctrl+C will not terminate QEMU any more but will be passed to the guest instead. braille Braille device. This will use BrlAPI to display the braille output on a real or fake device. msmouse Three button serial mouse. Configure the guest to use Mi- crosoft protocol. -parallel dev Redirect the virtual parallel port to host device dev (same devices as the serial port). On Linux hosts, /dev/parportN can be used to use hardware devices connected on the corresponding host parallel port. This option can be used several times to simulate up to 3 parallel ports. Use -parallel none to disable all parallel ports. -monitor dev Redirect the monitor to host device dev (same devices as the serial port). The default device is vc in graphical mode and stdio in non graphical mode. Use -monitor none to disable the default monitor. -qmp dev Like -monitor but opens in 'control' mode. For example, to make QMP available on localhost port 4444: -qmp tcp:localhost:4444,server=on,wait=off Not all options are configurable via this syntax; for maximum flexi- bility use the -mon option and an accompanying -chardev. -qmp-pretty dev Like -qmp but uses pretty JSON formatting. -mon [chardev=]name[,mode=readline|control][,pretty=on|off] Set up a monitor connected to the chardev name. QEMU supports two monitors: the Human Monitor Protocol (HMP; for human interaction), and the QEMU Monitor Protocol (QMP; a JSON RPC-style protocol). The default is HMP; mode=control selects QMP instead. pretty is only valid when mode=control, turning on JSON pretty printing to ease hu- man reading and debugging. For example: -chardev socket,id=mon1,host=localhost,port=4444,server=on,wait=off \ -mon chardev=mon1,mode=control,pretty=on enables the QMP monitor on localhost port 4444 with pretty-printing. -debugcon dev Redirect the debug console to host device dev (same devices as the serial port). The debug console is an I/O port which is typically port 0xe9; writing to that I/O port sends output to this device. The default device is vc in graphical mode and stdio in non graphical mode. -pidfile file Store the QEMU process PID in file. It is useful if you launch QEMU from a script. --preconfig Pause QEMU for interactive configuration before the machine is cre- ated, which allows querying and configuring properties that will af- fect machine initialization. Use QMP command 'x-exit-preconfig' to exit the preconfig state and move to the next state (i.e. run guest if -S isn't used or pause the second time if -S is used). This op- tion is experimental. -S Do not start CPU at startup (you must type 'c' in the monitor). -overcommit mem-lock=on|off|on-fault -overcommit cpu-pm=on|off Run qemu with hints about host resource overcommit. The default is to assume that host overcommits all resources. Locking qemu and guest memory can be enabled via mem-lock=on or mem-lock=on-fault (disabled by default). This works when host memory is not overcommitted and reduces the worst-case latency for guest. The on-fault option is better for reducing the memory footprint since it makes allocations lazy, but the pages still get locked in place once faulted by the guest or QEMU. Note that the two options are mutually exclusive. Guest ability to manage power state of host cpus (increasing latency for other processes on the same host cpu, but decreasing latency for guest) can be enabled via cpu-pm=on (disabled by default). This works best when host CPU is not overcommitted. When used, host esti- mates of CPU cycle and power utilization will be incorrect, not tak- ing into account guest idle time. -gdb dev Accept a gdb connection on device dev (see the GDB usage chapter in the System Emulation Users Guide). Note that this option does not pause QEMU execution -- if you want QEMU to not start the guest un- til you connect with gdb and issue a continue command, you will need to also pass the -S option to QEMU. The most usual configuration is to listen on a local TCP socket: -gdb tcp::3117 but you can specify other backends; UDP, pseudo TTY, or even stdio are all reasonable use cases. For example, a stdio connection allows you to start QEMU from within gdb and establish the connection via a pipe: (gdb) target remote | exec qemu-system-x86_64 -gdb stdio ... -s Shorthand for -gdb tcp::1234, i.e. open a gdbserver on TCP port 1234 (see the GDB usage chapter in the System Emulation Users Guide). -d item1[,...] Enable logging of specified items. Use '-d help' for a list of log items. -D logfile Output log in logfile instead of to stderr -dfilter range1[,...] Filter debug output to that relevant to a range of target addresses. The filter spec can be either start+size, start-size or start..end where start end and size are the addresses and sizes required. For example: -dfilter 0x8000..0x8fff,0xffffffc000080000+0x200,0xffffffc000060000-0x1000 Will dump output for any code in the 0x1000 sized block starting at 0x8000 and the 0x200 sized block starting at 0xffffffc000080000 and another 0x1000 sized block starting at 0xffffffc00005f000. -seed number Force the guest to use a deterministic pseudo-random number genera- tor, seeded with number. This does not affect crypto routines within the host. -L path Set the directory for the BIOS, VGA BIOS and keymaps. To list all the data directories, use -L help. -enable-kvm Enable KVM full virtualization support. This option is only avail- able if KVM support is enabled when compiling. -xen-domid id Specify xen guest domain id (XEN only). -xen-attach Attach to existing xen domain. libxl will use this when starting QEMU (XEN only). Restrict set of available xen operations to speci- fied domain id (XEN only). -no-reboot Exit instead of rebooting. -no-shutdown Don't exit QEMU on guest shutdown, but instead only stop the emula- tion. This allows for instance switching to monitor to commit changes to the disk image. -action event=action The action parameter serves to modify QEMU's default behavior when certain guest events occur. It provides a generic method for speci- fying the same behaviors that are modified by the -no-reboot and -no-shutdown parameters. Examples: -action panic=none -action reboot=shutdown,shutdown=pause -device i6300esb -action watchdog=pause -loadvm file Start right away with a saved state (loadvm in monitor) -daemonize Daemonize the QEMU process after initialization. QEMU will not de- tach from standard IO until it is ready to receive connections on any of its devices. This option is a useful way for external pro- grams to launch QEMU without having to cope with initialization race conditions. -option-rom file Load the contents of file as an option ROM. This option is useful to load things like EtherBoot. -rtc [base=utc|localtime|datetime][,clock=host|rt|vm][,driftfix=none|slew] Specify base as utc or localtime to let the RTC start at the current UTC or local time, respectively. localtime is required for correct date in MS-DOS or Windows. To start at a specific point in time, provide datetime in the format 2006-06-17T16:01:21 or 2006-06-17. The default base is UTC. By default the RTC is driven by the host system time. This allows using of the RTC as accurate reference clock inside the guest, specifically if the host time is smoothly following an accurate ex- ternal reference clock, e.g. via NTP. If you want to isolate the guest time from the host, you can set clock to rt instead, which provides a host monotonic clock if host support it. To even prevent the RTC from progressing during suspension, you can set clock to vm (virtual clock). 'clock=vm' is recommended especially in icount mode in order to preserve determinism; however, note that in icount mode the speed of the virtual clock is variable and can in general differ from the host clock. Enable driftfix (i386 targets only) if you experience time drift problems, specifically with Windows' ACPI HAL. This option will try to figure out how many timer interrupts were not processed by the Windows guest and will re-inject them. -icount [shift=N|auto][,align=on|off][,sleep=on|off][,rr=record|re- play,rrfile=filename[,rrsnapshot=snapshot]] Enable virtual instruction counter. The virtual cpu will execute one instruction every 2^N ns of virtual time. If auto is specified then the virtual cpu speed will be automatically adjusted to keep virtual time within a few seconds of real time. Note that while this option can give deterministic behavior, it does not provide cycle accurate emulation. Modern CPUs contain super- scalar out of order cores with complex cache hierarchies. The number of instructions executed often has little or no correlation with ac- tual performance. When the virtual cpu is sleeping, the virtual time will advance at default speed unless sleep=off is specified. With sleep=off, the virtual time will jump to the next timer deadline instantly whenever the virtual cpu goes to sleep mode and will not advance if no timer is enabled. This behavior gives deterministic execution times from the guest point of view. The default if icount is enabled is sleep=on. sleep=off cannot be used together with either shift=auto or align=on. align=on will activate the delay algorithm which will try to syn- chronise the host clock and the virtual clock. The goal is to have a guest running at the real frequency imposed by the shift option. Whenever the guest clock is behind the host clock and if align=on is specified then we print a message to the user to inform about the delay. Currently this option does not work when shift is auto. Note: The sync algorithm will work for those shift values for which the guest clock runs ahead of the host clock. Typically this happens when the shift value is high (how high depends on the host machine). The default if icount is enabled is align=off. When the rr option is specified deterministic record/replay is en- abled. The rrfile= option must also be provided to specify the path to the replay log. In record mode data is written to this file, and in replay mode it is read back. If the rrsnapshot option is given then it specifies a VM snapshot name. In record mode, a new VM snap- shot with the given name is created at the start of execution recording. In replay mode this option specifies the snapshot name used to load the initial VM state. -watchdog-action action The action controls what QEMU will do when the watchdog timer ex- pires. The default is reset (forcefully reset the guest). Other possible actions are: shutdown (attempt to gracefully shutdown the guest), poweroff (forcefully poweroff the guest), inject-nmi (inject a NMI into the guest), pause (pause the guest), debug (print a debug message and continue), or none (do nothing). Note that the shutdown action requires that the guest responds to ACPI signals, which it may not be able to do in the sort of situa- tions where the watchdog would have expired, and thus -watchdog-ac- tion shutdown is not recommended for production use. Examples: -device i6300esb -watchdog-action pause -echr numeric_ascii_value Change the escape character used for switching to the monitor when using monitor and serial sharing. The default is 0x01 when using the -nographic option. 0x01 is equal to pressing Control-a. You can se- lect a different character from the ascii control keys where 1 through 26 map to Control-a through Control-z. For instance you could use the either of the following to change the escape character to Control-t. -echr 0x14; -echr 20 The -incoming option specifies the migration channel for an incoming migra- tion. It may be used multiple times to specify multiple migration channel types. The channel type is specified in <channel>, or is 'main' for all other forms of -incoming. If multiple -incoming options are specified for a channel type, the last one takes precedence. -incoming tcp:[host]:port[,to=maxport][,ipv4=on|off][,ipv6=on|off] -incoming rdma:host:port[,ipv4=on|off][,ipv6=on|off] Prepare for incoming migration, listen on a given tcp port. -incoming unix:socketpath Prepare for incoming migration, listen on a given unix socket. -incoming fd:fd Accept incoming migration from a given file descriptor. -incoming file:filename[,offset=offset] Accept incoming migration from a given file starting at offset. offset allows the common size suffixes, or a 0x prefix, but not both. -incoming exec:cmdline Accept incoming migration as an output from specified external com- mand. -incoming <channel> Accept incoming migration on the migration channel. For the syntax of <channel>, see the QAPI documentation of MigrationChannel. Exam- ples: -incoming '{"channel-type": "main", "addr": { "transport": "socket", "type": "unix", "path": "my.sock" }}' -incoming main,addr.transport=socket,addr.type=unix,addr.path=my.sock -incoming defer Wait for the URI to be specified via migrate_incoming. The monitor can be used to change settings (such as migration parameters) prior to issuing the migrate_incoming to allow the migration to begin. -only-migratable Only allow migratable devices. Devices will not be allowed to enter an unmigratable state. -nodefaults Don't create default devices. Normally, QEMU sets the default de- vices like serial port, parallel port, virtual console, monitor de- vice, VGA adapter, floppy and CD-ROM drive and others. The -node- faults option will disable all those default devices. -prom-env variable=value Set OpenBIOS nvram variable to given value (PPC, SPARC only). qemu-system-sparc -prom-env 'auto-boot?=false' \ -prom-env 'boot-device=sd(0,2,0):d' -prom-env 'boot-args=linux single' qemu-system-ppc -prom-env 'auto-boot?=false' \ -prom-env 'boot-device=hd:2,\yaboot' \ -prom-env 'boot-args=conf=hd:2,\yaboot.conf' -semihosting Enable Semihosting mode (ARM, M68K, Xtensa, MIPS, RISC-V only). WARNING: Note that this allows guest direct access to the host filesystem, so should only be used with a trusted guest OS. See the -semihosting-config option documentation for further infor- mation about the facilities this enables. -semihosting-config [enable=on|off][,target=na- tive|gdb|auto][,chardev=id][,userspace=on|off][,arg=str[,...]] Enable and configure Semihosting (ARM, M68K, Xtensa, MIPS, RISC-V only). WARNING: Note that this allows guest direct access to the host filesystem, so should only be used with a trusted guest OS. target=native|gdb|auto Defines where the semihosting calls will be addressed, to QEMU (native) or to GDB (gdb). The default is auto, which means gdb during debug sessions and native otherwise. chardev=str1 Send the output to a chardev backend output for native or auto output when not in gdb userspace=on|off Allows code running in guest userspace to access the semi- hosting interface. The default is that only privileged guest code can make semihosting calls. Note that setting user- space=on should only be used if all guest code is trusted (for example, in bare-metal test case code). arg=str1,arg=str2,... Allows the user to pass input arguments, and can be used mul- tiple times to build up a list. The old-style -kernel/-append method of passing a command line is still supported for back- ward compatibility. If both the --semihosting-config arg and the -kernel/-append are specified, the former is passed to semihosting as it always takes precedence. -sandbox arg[,obsolete=string][,elevateprivi- leges=string][,spawn=string][,resourcecontrol=string] Enable Seccomp mode 2 system call filter. 'on' will enable syscall filtering and 'off' will disable it. The default is 'off'. obsolete=string Enable Obsolete system calls elevateprivileges=string Disable set*uid|gid system calls spawn=string Disable *fork and execve resourcecontrol=string Disable process affinity and schedular priority -readconfig file Read device configuration from file. This approach is useful when you want to spawn QEMU process with many command line options but you don't want to exceed the command line character limit. -no-user-config The -no-user-config option makes QEMU not load any of the user-pro- vided config files on sysconfdir. -trace [[enable=]pattern][,events=file][,file=file] Specify tracing options. [enable=]PATTERN Immediately enable events matching PATTERN (either event name or a globbing pattern). This option is only available if QEMU has been compiled with the simple, log or ftrace tracing backend. To specify multiple events or patterns, specify the -trace option multiple times. Use -trace help to print a list of names of trace points. events=FILE Immediately enable events listed in FILE. The file must contain one event name (as listed in the trace-events-all file) per line; globbing patterns are accepted too. This option is only avail- able if QEMU has been compiled with the simple, log or ftrace tracing backend. file=FILE Log output traces to FILE. This option is only available if QEMU has been compiled with the simple tracing backend. -plugin file=file[,argname=argvalue] Load a plugin. file=file Load the given plugin from a shared library file. argname=argvalue Argument passed to the plugin. (Can be given multiple times.) -run-with [async-teardown=on|off][,chroot=dir][,exit-with-par- ent=on|off][,user=username|uid:gid] Set QEMU process lifecycle options. async-teardown=on enables asynchronous teardown. A new process called "cleanup/<QEMU_PID>" will be created at startup sharing the address space with the main QEMU process, using clone. It will wait for the main QEMU process to terminate completely, and then exit. This allows QEMU to terminate very quickly even if the guest was huge, leaving the teardown of the address space to the cleanup process. Since the cleanup process shares the same cgroups as the main QEMU process, accounting is performed correctly. This only works if the cleanup process is not forcefully killed with SIGKILL before the main QEMU process has terminated completely. chroot=dir can be used for doing a chroot to the specified directory immediately before starting the guest execution. This is especially useful in combination with user=.... exit-with-parent=on causes QEMU to exit if the parent process of QEMU exits. This can be used when QEMU runs a captive appliance, where the lifetime of the appliance is scoped to the parent process. In case the parent process crashes, QEMU is still cleaned up. This only works on Linux, FreeBSD and macOS platforms. user=username or user=uid:gid can be used to drop root privileges before starting guest execution. QEMU will use the setuid and setgid system calls to switch to the specified identity. Note that the user=username syntax will also apply the full set of supplementary groups for the user, whereas the user=uid:gid will use only the gid group. -msg [timestamp=on|off][,guest-name=on|off] Control error message format. timestamp=on|off Prefix messages with a timestamp. Default is off. guest-name=on|off Prefix messages with guest name but only if -name guest op- tion is set otherwise the option is ignored. Default is off. -dump-vmstate file Dump json-encoded vmstate information for current machine type to file in file -enable-sync-profile Enable synchronization profiling. -perfmap Generate a map file for Linux perf tools that will allow basic pro- filing information to be broken down into basic blocks. -jitdump Generate a dump file for Linux perf tools that maps basic blocks to symbol names, line numbers and JITted code. Generic object creation -object typename[,prop1=value1,...] Create a new object of type typename setting properties in the order they are specified. Note that the 'id' property must be set. These objects are placed in the '/objects' path. -object memory-back- end-file,id=id,size=size,mem-path=dir,share=on|off,dis- card-data=on|off,merge=on|off,dump=on|off,preal- loc=on|off,host-nodes=host-nodes,policy=default|preferred|bind|in- terleave,align=align,offset=offset,readonly=on|off,rom=on|off|auto Creates a memory file backend object, which can be used to back the guest RAM with huge pages. The id parameter is a unique ID that will be used to refer- ence this memory region in other parameters, e.g. -numa, -de- vice nvdimm, etc. The size option provides the size of the memory region, and accepts common suffixes, e.g. 500M. The mem-path provides the path to either a shared memory or huge page filesystem mount. The share boolean option determines whether the memory region is marked as private to QEMU, or shared. The latter allows a co-operating external process to access the QEMU memory re- gion. Setting share=on might affect the ability to configure NUMA bindings for the memory backend under some circumstances, see Documentation/vm/numa_memory_policy.txt on the Linux kernel source tree for additional details. Setting the discard-data boolean option to on indicates that file contents can be destroyed when QEMU exits, to avoid un- necessarily flushing data to the backing file. Note that dis- card-data is only an optimization, and QEMU might not discard file contents if it aborts unexpectedly or is terminated us- ing SIGKILL. The merge boolean option enables memory merge, also known as MADV_MERGEABLE, so that Kernel Samepage Merging will consider the pages for memory deduplication. Setting the dump boolean option to off excludes the memory from core dumps. This feature is also known as MADV_DONTDUMP. The prealloc boolean option enables memory preallocation. The host-nodes option binds the memory range to a list of NUMA host nodes. The policy option sets the NUMA policy to one of the follow- ing values: default default host policy preferred prefer the given host node list for allocation bind restrict memory allocation to the given host node list interleave interleave memory allocations across the given host node list The align option specifies the base address alignment when QEMU mmap(2) mem-path, and accepts common suffixes, eg 2M. Some backend store specified by mem-path requires an align- ment different than the default one used by QEMU, eg the de- vice DAX /dev/dax0.0 requires 2M alignment rather than 4K. In such cases, users can specify the required alignment via this option. The offset option specifies the offset into the target file that the region starts at. You can use this parameter to back multiple regions with a single file. The pmem option specifies whether the backing file specified by mem-path is in host persistent memory that can be accessed using the SNIA NVM programming model (e.g. Intel NVDIMM). If pmem is set to 'on', QEMU will take necessary operations to guarantee the persistence of its own writes to mem-path (e.g. in vNVDIMM label emulation and live migration). Also, we will map the backend-file with MAP_SYNC flag, which ensures the file metadata is in sync for mem-path in case of host crash or a power failure. MAP_SYNC requires support from both the host kernel (since Linux kernel 4.15) and the filesystem of mem-path mounted with DAX option. The readonly option specifies whether the backing file is opened read-only or read-write (default). The rom option specifies whether to create Read Only Memory (ROM) that cannot be modified by the VM. Any write attempts to such ROM will be denied. Most use cases want proper RAM instead of ROM. However, selected use cases, like R/O NVDIMMs, can benefit from ROM. If set to on, create ROM; if set to off, create writable RAM; if set to auto (default), the value of the readonly option is used. This option is pri- marily helpful when we want to have writable RAM in configu- rations that would traditionally create ROM before the rom option was introduced: VM templating, where we want to open a file readonly (readonly=on) and mark the memory to be private for QEMU (share=off). For this use case, we need writable RAM instead of ROM, and want to also set rom=off. -object memory-back- end-ram,id=id,merge=on|off,dump=on|off,share=on|off,preal- loc=on|off,size=size,host-nodes=host-nodes,policy=default|pre- ferred|bind|interleave Creates a memory backend object, which can be used to back the guest RAM. Memory backend objects offer more control than the -m option that is traditionally used to define guest RAM. Please refer to memory-backend-file for a description of the options. -object memory-back- end-memfd,id=id,merge=on|off,dump=on|off,share=on|off,preal- loc=on|off,size=size,host-nodes=host-nodes,policy=default|pre- ferred|bind|interleave,seal=on|off,hugetlb=on|off,hugetlbsize=size Creates an anonymous memory file backend object, which allows QEMU to share the memory with an external process (e.g. when using vhost-user). The memory is allocated with memfd and op- tional sealing. (Linux only) The seal option creates a sealed-file, that will block fur- ther resizing the memory ('on' by default). The hugetlb option specify the file to be created resides in the hugetlbfs filesystem (since Linux 4.14). Used in conjunc- tion with the hugetlb option, the hugetlbsize option specify the hugetlb page size on systems that support multiple hugetlb page sizes (it must be a power of 2 value supported by the system). In some versions of Linux, the hugetlb option is incompatible with the seal option (requires at least Linux 4.16). Please refer to memory-backend-file for a description of the other options. The share boolean option is on by default with memfd. -object memory-back- end-shm,id=id,merge=on|off,dump=on|off,share=on|off,preal- loc=on|off,size=size,host-nodes=host-nodes,policy=default|pre- ferred|bind|interleave Creates a POSIX shared memory backend object, which allows QEMU to share the memory with an external process (e.g. when using vhost-user). memory-backend-shm is a more portable and less featureful version of memory-backend-memfd. It can then be used in any POSIX system, especially when memfd is not supported. Please refer to memory-backend-file for a description of the options. The share boolean option is on by default with shm. Setting it to off will cause a failure during allocation because it is not supported by this backend. -object iommufd,id=id[,fd=fd] Creates an iommufd backend which allows control of DMA map- ping through the /dev/iommu device. The id parameter is a unique ID which frontends (such as vfio-pci of vdpa) will use to connect with the iommufd back- end. The fd parameter is an optional pre-opened file descriptor resulting from /dev/iommu opening. Usually the iommufd is shared across all subsystems, bringing the benefit of cen- tralized reference counting. -object rng-builtin,id=id Creates a random number generator backend which obtains en- tropy from QEMU builtin functions. The id parameter is a unique ID that will be used to reference this entropy backend from the virtio-rng device. By default, the virtio-rng device uses this RNG backend. -object rng-random,id=id,filename=/dev/random Creates a random number generator backend which obtains en- tropy from a device on the host. The id parameter is a unique ID that will be used to reference this entropy backend from the virtio-rng device. The filename parameter specifies which file to obtain entropy from and if omitted defaults to /dev/urandom. -object rng-egd,id=id,chardev=chardevid Creates a random number generator backend which obtains en- tropy from an external daemon running on the host. The id pa- rameter is a unique ID that will be used to reference this entropy backend from the virtio-rng device. The chardev para- meter is the unique ID of a character device backend that provides the connection to the RNG daemon. -object tls-creds-anon,id=id,endpoint=end- point,dir=/path/to/cred/dir,verify-peer=on|off Creates a TLS anonymous credentials object, which can be used to provide TLS support on network backends. The id parameter is a unique ID which network backends will use to access the credentials. The endpoint is either server or client depend- ing on whether the QEMU network backend that uses the creden- tials will be acting as a client or as a server. If ver- ify-peer is enabled (the default) then once the handshake is completed, the peer credentials will be verified, though this is a no-op for anonymous credentials. The dir parameter tells QEMU where to find the credential files. For server endpoints, this directory may contain a file dh-params.pem providing diffie-hellman parameters to use for the TLS server. If the file is missing, QEMU will gener- ate a set of DH parameters at startup. This is a computation- ally expensive operation that consumes random pool entropy, so it is recommended that a persistent set of parameters be generated upfront and saved. -object tls-creds-psk,id=id,endpoint=end- point,dir=/path/to/keys/dir[,username=username] Creates a TLS Pre-Shared Keys (PSK) credentials object, which can be used to provide TLS support on network backends. The id parameter is a unique ID which network backends will use to access the credentials. The endpoint is either server or client depending on whether the QEMU network backend that uses the credentials will be acting as a client or as a server. For clients only, username is the username which will be sent to the server. If omitted it defaults to "qemu". The dir parameter tells QEMU where to find the keys file. It is called "dir/keys.psk" and contains "username:key" pairs. This file can most easily be created using the GnuTLS psktool program. For server endpoints, dir may also contain a file dh-params.pem providing diffie-hellman parameters to use for the TLS server. If the file is missing, QEMU will generate a set of DH parameters at startup. This is a computationally expensive operation that consumes random pool entropy, so it is recommended that a persistent set of parameters be gener- ated up front and saved. -object tls-creds-x509,id=id,endpoint=end- point,dir=/path/to/cred/dir,priority=priority,ver- ify-peer=on|off,passwordid=id Creates a TLS anonymous credentials object, which can be used to provide TLS support on network backends. The id parameter is a unique ID which network backends will use to access the credentials. The endpoint is either server or client depend- ing on whether the QEMU network backend that uses the creden- tials will be acting as a client or as a server. If ver- ify-peer is enabled (the default) then once the handshake is completed, the peer credentials will be verified. With x509 certificates, this implies that the clients must be provided with valid client certificates too. The dir parameter tells QEMU where to find the credential files. For server endpoints, this directory may contain a file dh-params.pem providing diffie-hellman parameters to use for the TLS server. If the file is missing, QEMU will gener- ate a set of DH parameters at startup. This is a computation- ally expensive operation that consumes random pool entropy, so it is recommended that a persistent set of parameters be generated upfront and saved. For x509 certificate credentials the directory will contain further files providing the x509 certificates. The certifi- cates must be stored in PEM format, in filenames ca-cert.pem, ca-crl.pem (optional), server-cert.pem (only servers), server-key.pem (only servers), client-cert.pem (only clients), and client-key.pem (only clients). For the server-key.pem and client-key.pem files which contain sensitive private keys, it is possible to use an encrypted version by providing the passwordid parameter. This provides the ID of a previously created secret object containing the password for decryption. The priority parameter allows to override the global default priority used by gnutls. This can be useful if the system ad- ministrator needs to use a weaker set of crypto priorities for QEMU without potentially forcing the weakness onto all applications. Or conversely if one wants wants a stronger de- fault for QEMU than for all other applications, they can do this through this parameter. Its format is a gnutls priority string as described at - https://gnutls.org/manual/html_node/Priority-Strings.html. -object tls-cipher-suites,id=id,priority=priority Creates a TLS cipher suites object, which can be used to con- trol the TLS cipher/protocol algorithms that applications are permitted to use. The id parameter is a unique ID which frontends will use to access the ordered list of permitted TLS cipher suites from the host. The priority parameter allows to override the global default priority used by gnutls. This can be useful if the system ad- ministrator needs to use a weaker set of crypto priorities for QEMU without potentially forcing the weakness onto all applications. Or conversely if one wants wants a stronger de- fault for QEMU than for all other applications, they can do this through this parameter. Its format is a gnutls priority string as described at - https://gnutls.org/manual/html_node/Priority-Strings.html. An example of use of this object is to control UEFI HTTPS Boot. The tls-cipher-suites object exposes the ordered list of permitted TLS cipher suites from the host side to the guest firmware, via fw_cfg. The list is represented as an ar- ray of IANA_TLS_CIPHER objects. The firmware uses the IANA_TLS_CIPHER array for configuring guest-side TLS. In the following example, the priority at which the host-side policy is retrieved is given by the priority property. Given that QEMU uses GNUTLS, priority=@SYSTEM may be used to refer to /etc/crypto-policies/back-ends/gnutls.config. # qemu-system-x86_64 \ -object tls-cipher-suites,id=mysuite0,priority=@SYSTEM \ -fw_cfg name=etc/edk2/https/ciphers,gen_id=mysuite0 -object filter-buffer,id=id,netdev=netdevid,inter- val=t[,queue=all|rx|tx][,status=on|off][,posi- tion=head|tail|id=<id>][,insert=behind|before] Interval t can't be 0, this filter batches the packet deliv- ery: all packets arriving in a given interval on netdev net- devid are delayed until the end of the interval. Interval is in microseconds. status is optional that indicate whether the netfilter is on (enabled) or off (disabled), the default sta- tus for netfilter will be 'on'. queue all|rx|tx is an option that can be applied to any net- filter. all: the filter is attached both to the receive and the transmit queue of the netdev (default). rx: the filter is attached to the receive queue of the net- dev, where it will receive packets sent to the netdev. tx: the filter is attached to the transmit queue of the net- dev, where it will receive packets sent by the netdev. position head|tail|id=<id> is an option to specify where the filter should be inserted in the filter list. It can be ap- plied to any netfilter. head: the filter is inserted at the head of the filter list, before any existing filters. tail: the filter is inserted at the tail of the filter list, behind any existing filters (default). id=<id>: the filter is inserted before or behind the filter specified by <id>, see the insert option below. insert behind|before is an option to specify where to insert the new filter relative to the one specified with posi- tion=id=<id>. It can be applied to any netfilter. before: insert before the specified filter. behind: insert behind the specified filter (default). -object filter-mirror,id=id,netdev=netdevid,outdev=charde- vid,queue=all|rx|tx[,vnet_hdr_support][,posi- tion=head|tail|id=<id>][,insert=behind|before] filter-mirror on netdev netdevid,mirror net packet to charde- vchardevid, if it has the vnet_hdr_support flag, filter-mir- ror will mirror packet with vnet_hdr_len. -object filter-redirector,id=id,netdev=netdevid,indev=chardevid,out- dev=chardevid,queue=all|rx|tx[,vnet_hdr_support][,posi- tion=head|tail|id=<id>][,insert=behind|before] filter-redirector on netdev netdevid,redirect filter's net packet to chardev chardevid,and redirect indev's packet to filter.if it has the vnet_hdr_support flag, filter-redirector will redirect packet with vnet_hdr_len. Create a filter-redi- rector we need to differ outdev id from indev id, id can not be the same. we can just use indev or outdev, but at least one of indev or outdev need to be specified. -object filter-rewriter,id=id,netdev=netde- vid,queue=all|rx|tx,[vnet_hdr_support][,posi- tion=head|tail|id=<id>][,insert=behind|before] Filter-rewriter is a part of COLO project.It will rewrite tcp packet to secondary from primary to keep secondary tcp con- nection,and rewrite tcp packet to primary from secondary make tcp packet can be handled by client.if it has the vnet_hdr_support flag, we can parse packet with vnet header. usage: colo secondary: -object filter-redirector,id=f1,net- dev=hn0,queue=tx,indev=red0 -object filter-redirec- tor,id=f2,netdev=hn0,queue=rx,outdev=red1 -object fil- ter-rewriter,id=rew0,netdev=hn0,queue=all -object filter-dump,id=id,netdev=dev[,file=file- name][,maxlen=len][,position=head|tail|id=<id>][,insert=behind|be- fore] Dump the network traffic on netdev dev to the file specified by filename. At most len bytes (64k by default) per packet are stored. The file format is libpcap, so it can be analyzed with tools such as tcpdump or Wireshark. -object colo-compare,id=<id>,primary_in=<chardevid>,sec- ondary_in=<chardevid>,outdev=<chardevid>,io- thread=<id>[,vnet_hdr_support][,notify_dev=<id>][,compare_time- out=<time_ms>][,expired_scan_cycle=<time_ms>][,max_queue_size=<max- size>] Colo-compare gets packets from the chardev backends specified by primary_in and secondary_in, and compares whether the pay- loads of the primary packet and the secondary packet are the same. If they match, it will output the primary packet to the chardev backend specified by outdev; otherwise it will notify COLO-framework to do a checkpoint and send the primary packet to outdev. In order to improve efficiency, we need to put the task of comparison in another iothread; the iothread option specifies that iothread object (which your commandline should create). The vnet_hdr_support flag tells colo compare to pass the vnet header length when it sends and receives packets. The compare_timeout option sets the maximum time that colo-compare will hold the packet for, in ms. The expired_scan_cycle option sets the period of scanning ex- pired primary node network packets, in ms. The max_queue_size option sets the max compare queue size. If you want to use Xen COLO, you need to specify notify_dev to tell colo-compare how to notify Xen colo-frame to do a checkpoint. COLO-compare must be used with the help of filter-mirror, filter-redirector and filter-rewriter. KVM COLO primary: -netdev tap,id=hn0,vhost=off -device e1000,id=e0,netdev=hn0,mac=52:a4:00:12:78:66 -chardev socket,id=mirror0,host=3.3.3.3,port=9003,server=on,wait=off -chardev socket,id=compare1,host=3.3.3.3,port=9004,server=on,wait=off -chardev socket,id=compare0,host=3.3.3.3,port=9001,server=on,wait=off -chardev socket,id=compare0-0,host=3.3.3.3,port=9001 -chardev socket,id=compare_out,host=3.3.3.3,port=9005,server=on,wait=off -chardev socket,id=compare_out0,host=3.3.3.3,port=9005 -object iothread,id=iothread1 -object filter-mirror,id=m0,netdev=hn0,queue=tx,outdev=mirror0 -object filter-redirector,netdev=hn0,id=redire0,queue=rx,indev=compare_out -object filter-redirector,netdev=hn0,id=redire1,queue=rx,outdev=compare0 -object colo-compare,id=comp0,primary_in=compare0-0,secondary_in=compare1,outdev=compare_out0,iothread=iothread1 secondary: -netdev tap,id=hn0,vhost=off -device e1000,netdev=hn0,mac=52:a4:00:12:78:66 -chardev socket,id=red0,host=3.3.3.3,port=9003 -chardev socket,id=red1,host=3.3.3.3,port=9004 -object filter-redirector,id=f1,netdev=hn0,queue=tx,indev=red0 -object filter-redirector,id=f2,netdev=hn0,queue=rx,outdev=red1 Xen COLO primary: -netdev tap,id=hn0,vhost=off -device e1000,id=e0,netdev=hn0,mac=52:a4:00:12:78:66 -chardev socket,id=mirror0,host=3.3.3.3,port=9003,server=on,wait=off -chardev socket,id=compare1,host=3.3.3.3,port=9004,server=on,wait=off -chardev socket,id=compare0,host=3.3.3.3,port=9001,server=on,wait=off -chardev socket,id=compare0-0,host=3.3.3.3,port=9001 -chardev socket,id=compare_out,host=3.3.3.3,port=9005,server=on,wait=off -chardev socket,id=compare_out0,host=3.3.3.3,port=9005 -chardev socket,id=notify_way,host=3.3.3.3,port=9009,server=on,wait=off -object filter-mirror,id=m0,netdev=hn0,queue=tx,outdev=mirror0 -object filter-redirector,netdev=hn0,id=redire0,queue=rx,indev=compare_out -object filter-redirector,netdev=hn0,id=redire1,queue=rx,outdev=compare0 -object iothread,id=iothread1 -object colo-compare,id=comp0,primary_in=compare0-0,secondary_in=compare1,outdev=compare_out0,notify_dev=notify_way,iothread=iothread1 secondary: -netdev tap,id=hn0,vhost=off -device e1000,netdev=hn0,mac=52:a4:00:12:78:66 -chardev socket,id=red0,host=3.3.3.3,port=9003 -chardev socket,id=red1,host=3.3.3.3,port=9004 -object filter-redirector,id=f1,netdev=hn0,queue=tx,indev=red0 -object filter-redirector,id=f2,netdev=hn0,queue=rx,outdev=red1 If you want to know the detail of above command line, you can read the colo-compare git log. -object cryptodev-backend-builtin,id=id[,queues=queues] Creates a cryptodev backend which executes crypto operations from the QEMU cipher APIs. The id parameter is a unique ID that will be used to reference this cryptodev backend from the virtio-crypto device. The queues parameter is optional, which specify the queue number of cryptodev backend, the de- fault of queues is 1. # qemu-system-x86_64 \ [...] \ -object cryptodev-backend-builtin,id=cryptodev0 \ -device virtio-crypto-pci,id=crypto0,cryptodev=cryptodev0 \ [...] -object cryptodev-vhost-user,id=id,chardev=chardevid[,queues=queues] Creates a vhost-user cryptodev backend, backed by a chardev chardevid. The id parameter is a unique ID that will be used to reference this cryptodev backend from the virtio-crypto device. The chardev should be a unix domain socket backed one. The vhost-user uses a specifically defined protocol to pass vhost ioctl replacement messages to an application on the other end of the socket. The queues parameter is op- tional, which specify the queue number of cryptodev backend for multiqueue vhost-user, the default of queues is 1. # qemu-system-x86_64 \ [...] \ -chardev socket,id=chardev0,path=/path/to/socket \ -object cryptodev-vhost-user,id=cryptodev0,chardev=chardev0 \ -device virtio-crypto-pci,id=crypto0,cryptodev=cryptodev0 \ [...] -object secret,id=id,data=string,format=raw|base64[,keyid=se- cretid,iv=string] -object secret,id=id,file=filename,format=raw|base64[,keyid=se- cretid,iv=string] Defines a secret to store a password, encryption key, or some other sensitive data. The sensitive data can either be passed directly via the data parameter, or indirectly via the file parameter. Using the data parameter is insecure unless the sensitive data is encrypted. The sensitive data can be provided in raw format (the de- fault), or base64. When encoded as JSON, the raw format only supports valid UTF-8 characters, so base64 is recommended for sending binary data. QEMU will convert from which ever format is provided to the format it needs internally. eg, an RBD password can be provided in raw format, even though it will be base64 encoded when passed onto the RBD sever. For added protection, it is possible to encrypt the data as- sociated with a secret using the AES-256-CBC cipher. Use of encryption is indicated by providing the keyid and iv parame- ters. The keyid parameter provides the ID of a previously de- fined secret that contains the AES-256 decryption key. This key should be 32-bytes long and be base64 encoded. The iv pa- rameter provides the random initialization vector used for encryption of this particular secret and should be a base64 encrypted string of the 16-byte IV. The simplest (insecure) usage is to provide the secret inline # qemu-system-x86_64 -object secret,id=sec0,data=letmein,format=raw The simplest secure usage is to provide the secret via a file # printf "letmein" > mypasswd.txt # QEMU_SYSTEM_MACRO -object secret,id=sec0,file=mypasswd.txt,format=raw For greater security, AES-256-CBC should be used. To illus- trate usage, consider the openssl command line tool which can encrypt the data. Note that when encrypting, the plaintext must be padded to the cipher block size (32 bytes) using the standard PKCS#5/6 compatible padding algorithm. First a master key needs to be created in base64 encoding: # openssl rand -base64 32 > key.b64 # KEY=$(base64 -d key.b64 | hexdump -v -e '/1 "%02X"') Each secret to be encrypted needs to have a random initial- ization vector generated. These do not need to be kept secret # openssl rand -base64 16 > iv.b64 # IV=$(base64 -d iv.b64 | hexdump -v -e '/1 "%02X"') The secret to be defined can now be encrypted, in this case we're telling openssl to base64 encode the result, but it could be left as raw bytes if desired. # SECRET=$(printf "letmein" | openssl enc -aes-256-cbc -a -K $KEY -iv $IV) When launching QEMU, create a master secret pointing to key.b64 and specify that to be used to decrypt the user pass- word. Pass the contents of iv.b64 to the second secret # qemu-system-x86_64 \ -object secret,id=secmaster0,format=base64,file=key.b64 \ -object secret,id=sec0,keyid=secmaster0,format=base64,\ data=$SECRET,iv=$(<iv.b64) -object sev-guest,id=id,cbitpos=cbitpos,re- duced-phys-bits=val,[sev-device=string,policy=policy,handle=han- dle,dh-cert-file=file,session-file=file,kernel-hashes=on|off] Create a Secure Encrypted Virtualization (SEV) guest object, which can be used to provide the guest memory encryption sup- port on AMD processors. When memory encryption is enabled, one of the physical ad- dress bit (aka the C-bit) is utilized to mark if a memory page is protected. The cbitpos is used to provide the C-bit position. The C-bit position is Host family dependent hence user must provide this value. On EPYC, the value should be 47. When memory encryption is enabled, we loose certain bits in physical address space. The reduced-phys-bits is used to pro- vide the number of bits we loose in physical address space. Similar to C-bit, the value is Host family dependent. On EPYC, a guest will lose a maximum of 1 bit, so the value should be 1. The sev-device provides the device file to use for communi- cating with the SEV firmware running inside AMD Secure Processor. The default device is '/dev/sev'. If hardware sup- ports memory encryption then /dev/sev devices are created by CCP driver. The policy provides the guest policy to be enforced by the SEV firmware and restrict what configuration and operational commands can be performed on this guest by the hypervisor. The policy should be provided by the guest owner and is bound to the guest and cannot be changed throughout the lifetime of the guest. The default is 0. If guest policy allows sharing the key with another SEV guest then handle can be use to provide handle of the guest from which to share the key. The dh-cert-file and session-file provides the guest owner's Public Diffie-Hillman key defined in SEV spec. The PDH and session parameters are used for establishing a cryptographic session with the guest owner to negotiate keys used for at- testation. The file must be encoded in base64. The kernel-hashes adds the hashes of given kernel/initrd/ cmdline to a designated guest firmware page for measured Linux boot with -kernel. The default is off. (Since 6.2) e.g to launch a SEV guest # qemu-system-x86_64 \ ...... \ -object sev-guest,id=sev0,cbitpos=47,reduced-phys-bits=1 \ -machine ...,memory-encryption=sev0 \ ..... -object igvm-cfg,file=file Create an IGVM configuration object that defines the initial state of the guest using a file in that conforms to the Inde- pendent Guest Virtual Machine (IGVM) file format. This is currently only supported by -machine q35 and -machine pc. The file parameter is used to specify the IGVM file to load. When provided, the IGVM file is used to populate the initial memory of the virtual machine and, depending on the platform, can define the initial processor state, memory map and para- meters. The IGVM file is expected to contain the firmware for the virtual machine, therefore an igvm-cfg object cannot be pro- vided along with other ways of specifying firmware, such as the -bios parameter on x86 machines. e.g to launch a machine providing the firmware in an IGVM file # qemu-system-x86_64 \ ...... \ -object igvm-cfg,id=igvm0,file=bios.igvm \ -machine ...,igvm-cfg=igvm0 \ ..... -object authz-simple,id=id,identity=string Create an authorization object that will control access to network services. The identity parameter is identifies the user and its format depends on the network service that authorization object is associated with. For authorizing based on TLS x509 certifi- cates, the identity must be the x509 distinguished name. Note that care must be taken to escape any commas in the distin- guished name. An example authorization object to validate a x509 distin- guished name would look like: # qemu-system-x86_64 \ ... \ -object 'authz-simple,id=auth0,identity=CN=laptop.example.com,,O=Example Org,,L=London,,ST=London,,C=GB' \ ... Note the use of quotes due to the x509 distinguished name containing whitespace, and escaping of ','. -object authz-listfile,id=id,filename=path,refresh=on|off Create an authorization object that will control access to network services. The filename parameter is the fully qualified path to a file containing the access control list rules in JSON format. An example set of rules that match against SASL usernames might look like: { "rules": [ { "match": "fred", "policy": "allow", "format": "exact" }, { "match": "bob", "policy": "allow", "format": "exact" }, { "match": "danb", "policy": "deny", "format": "glob" }, { "match": "dan*", "policy": "allow", "format": "exact" }, ], "policy": "deny" } When checking access the object will iterate over all the rules and the first rule to match will have its policy value returned as the result. If no rules match, then the default policy value is returned. The rules can either be an exact string match, or they can use the simple UNIX glob pattern matching to allow wildcards to be used. If refresh is set to true the file will be monitored and au- tomatically reloaded whenever its content changes. As with the authz-simple object, the format of the identity strings being matched depends on the network service, but is usually a TLS x509 distinguished name, or a SASL username. An example authorization object to validate a SASL username would look like: # qemu-system-x86_64 \ ... \ -object authz-simple,id=auth0,filename=/etc/qemu/vnc-sasl.acl,refresh=on \ ... -object authz-pam,id=id,service=string Create an authorization object that will control access to network services. The service parameter provides the name of a PAM service to use for authorization. It requires that a file /etc/pam.d/service exist to provide the configuration for the account subsystem. An example authorization object to validate a TLS x509 dis- tinguished name would look like: # qemu-system-x86_64 \ ... \ -object authz-pam,id=auth0,service=qemu-vnc \ ... There would then be a corresponding config file for PAM at /etc/pam.d/qemu-vnc that contains: account requisite pam_listfile.so item=user sense=allow \ file=/etc/qemu/vnc.allow Finally the /etc/qemu/vnc.allow file would contain the list of x509 distinguished names that are permitted access CN=laptop.example.com,O=Example Home,L=London,ST=London,C=GB -object io- thread,id=id,poll-max-ns=poll-max-ns,poll-grow=poll-grow,poll-shrink=poll-shrink,aio-max-batch=aio-max-batch Creates a dedicated event loop thread that devices can be as- signed to. This is known as an IOThread. By default device emulation happens in vCPU threads or the main event loop thread. This can become a scalability bottleneck. IOThreads allow device emulation and I/O to run on other host CPUs. The id parameter is a unique ID that will be used to refer- ence this IOThread from -device ...,iothread=id. Multiple devices can be assigned to an IOThread. Note that not all de- vices support an iothread parameter. The query-iothreads QMP command lists IOThreads and reports their thread IDs so that the user can configure host CPU pin- ning/affinity. IOThreads use an adaptive polling algorithm to reduce event loop latency. Instead of entering a blocking system call to monitor file descriptors and then pay the cost of being woken up when an event occurs, the polling algorithm spins waiting for events for a short time. The algorithm's default parame- ters are suitable for many cases but can be adjusted based on knowledge of the workload and/or host device latency. The poll-max-ns parameter is the maximum number of nanosec- onds to busy wait for events. Polling can be disabled by set- ting this value to 0. The poll-grow parameter is the multiplier used to increase the polling time when the algorithm detects it is missing events due to not polling long enough. The poll-shrink parameter is the divisor used to decrease the polling time when the algorithm detects it is spending too long polling without encountering events. The aio-max-batch parameter is the maximum number of requests in a batch for the AIO engine, 0 means that the engine will use its default. The IOThread parameters can be modified at run-time using the qom-set command (where iothread1 is the IOThread's id): (qemu) qom-set /objects/iothread1 poll-max-ns 100000 During the graphical emulation, you can use special key combinations from the following table to change modes. By default the modifier is Ctrl+Alt (used in the table below) which can be changed with -display suboption mod= where appropriate. For example, -display sdl, grab-mod=lshift-lctrl-lalt changes the modifier key to Ctrl+Alt+Shift, while -display sdl,grab-mod=rc- trl changes it to the right Ctrl key. MULTIPLEXER KEYS +--------------+-----------------------------+ | Key Sequence | Action | +--------------+-----------------------------+ | Ctrl+Alt+f | Toggle full screen | +--------------+-----------------------------+ | Ctrl+Alt++ | Enlarge the screen | +--------------+-----------------------------+ | Ctrl+Alt+- | Shrink the screen | +--------------+-----------------------------+ | Ctrl+Alt+0 | Restore the screen's | | | un-scaled dimensions | +--------------+-----------------------------+ | Ctrl+Alt+n | Switch to virtual console | | | 'n'. Standard console map- | | | pings are: | | | | | | * 1: Target system | | | display | | | | | | * 2: Monitor | | | | | | * 3: Serial port | +--------------+-----------------------------+ | Ctrl+Alt+g | Toggle mouse and keyboard | | | grab. | +--------------+-----------------------------+ In the virtual consoles, you can use Ctrl+Up, Ctrl+Down, Ctrl+PageUp and Ctrl+PageDown to move in the back log. During emulation, if you are using a character backend multiplexer (which is the default if you are using -nographic) then several commands are available via an escape sequence. These key sequences all start with an es- cape character, which is Ctrl+a by default, but can be changed with -echr. The list below assumes you're using the default. MULTIPLEXER KEYS +---------------+-----------------------------+ | Key Sequence | Action | +---------------+-----------------------------+ | Ctrl+a h | Print this help | +---------------+-----------------------------+ | Ctrl+a x | Exit emulator | +---------------+-----------------------------+ | Ctrl+a s | Save disk data back to file | | | (if -snapshot) | +---------------+-----------------------------+ | Ctrl+a t | Toggle console timestamps | +---------------+-----------------------------+ | Ctrl+a b | Send break (magic sysrq in | | | Linux) | +---------------+-----------------------------+ | Ctrl+a c | Rotate between the fron- | | | tends connected to the mul- | | | tiplexer (usually this | | | switches between the moni- | | | tor and the console) | +---------------+-----------------------------+ | Ctrl+a Ctrl+a | Send the escape character | | | to the frontend | +---------------+-----------------------------+ NOTES In addition to using normal file images for the emulated storage devices, QEMU can also use networked resources such as iSCSI devices. These are specified using a special URL syntax. iSCSI iSCSI support allows QEMU to access iSCSI resources directly and use as images for the guest storage. Both disk and cdrom images are sup- ported. Syntax for specifying iSCSI LUNs is "iscsi://<tar- get-ip>[:<port>]/<target-iqn>/<lun>" By default qemu will use the iSCSI initiator-name 'iqn.2008-11.org.linux-kvm[:<name>]' but this can also be set from the command line or a configuration file. Since version QEMU 2.4 it is possible to specify a iSCSI request timeout to detect stalled requests and force a reestablishment of the session. The timeout is specified in seconds. The default is 0 which means no timeout. Libiscsi 1.15.0 or greater is required for this feature. Example (without authentication): qemu-system-x86_64 -iscsi initiator-name=iqn.2001-04.com.example:my-initiator \ -cdrom iscsi://192.0.2.1/iqn.2001-04.com.example/2 \ -drive file=iscsi://192.0.2.1/iqn.2001-04.com.example/1 Example (CHAP username/password via URL): qemu-system-x86_64 -drive file=iscsi://user%password@192.0.2.1/iqn.2001-04.com.example/1 Example (CHAP username/password via environment variables): LIBISCSI_CHAP_USERNAME="user" \ LIBISCSI_CHAP_PASSWORD="password" \ qemu-system-x86_64 -drive file=iscsi://192.0.2.1/iqn.2001-04.com.example/1 NBD QEMU supports NBD (Network Block Devices) both using TCP protocol as well as Unix Domain Sockets. With TCP, the default port is 10809. Syntax for specifying a NBD device using TCP, in preferred URI form: "nbd://<server-ip>[:<port>]/[<export>]" Syntax for specifying a NBD device using Unix Domain Sockets; remem- ber that '?' is a shell glob character and may need quoting: "nbd+unix:///[<export>]?socket=<domain-socket>" Older syntax that is also recognized: "nbd:<server-ip>:<port>[:ex- portname=<export>]" Syntax for specifying a NBD device using Unix Domain Sockets "nbd:unix:<domain-socket>[:exportname=<export>]" Example for TCP qemu-system-x86_64 --drive file=nbd:192.0.2.1:30000 Example for Unix Domain Sockets qemu-system-x86_64 --drive file=nbd:unix:/tmp/nbd-socket SSH QEMU supports SSH (Secure Shell) access to remote disks. Examples: qemu-system-x86_64 -drive file=ssh://user@host/path/to/disk.img qemu-system-x86_64 -drive file.driver=ssh,file.user=user,file.host=host,file.port=22,file.path=/path/to/disk.img Currently authentication must be done using ssh-agent. Other authen- tication methods may be supported in future. GlusterFS GlusterFS is a user space distributed file system. QEMU supports the use of GlusterFS volumes for hosting VM disk images using TCP and Unix Domain Sockets transport protocols. Syntax for specifying a VM disk image on GlusterFS volume is URI: gluster[+type]://[host[:port]]/volume/path[?socket=...][,debug=N][,logfile=...] JSON: 'json:{"driver":"qcow2","file":{"driver":"gluster","volume":"testvol","path":"a.img","debug":N,"logfile":"...", "server":[{"type":"tcp","host":"...","port":"..."}, {"type":"unix","socket":"..."}]}}' Example URI: qemu-system-x86_64 --drive file=gluster://192.0.2.1/testvol/a.img, file.debug=9,file.logfile=/var/log/qemu-gluster.log JSON: qemu-system-x86_64 'json:{"driver":"qcow2", "file":{"driver":"gluster", "volume":"testvol","path":"a.img", "debug":9,"logfile":"/var/log/qemu-gluster.log", "server":[{"type":"tcp","host":"1.2.3.4","port":24007}, {"type":"unix","socket":"/var/run/glusterd.socket"}]}}' qemu-system-x86_64 -drive driver=qcow2,file.driver=gluster,file.volume=testvol,file.path=/path/a.img, file.debug=9,file.logfile=/var/log/qemu-gluster.log, file.server.0.type=tcp,file.server.0.host=1.2.3.4,file.server.0.port=24007, file.server.1.type=unix,file.server.1.socket=/var/run/glusterd.socket See also http://www.gluster.org. HTTP/HTTPS/FTP/FTPS QEMU supports read-only access to files accessed over http(s) and ftp(s). Syntax using a single filename: <protocol>://[<username>[:<password>]@]<host>/<path> where: protocol 'http', 'https', 'ftp', or 'ftps'. username Optional username for authentication to the remote server. password Optional password for authentication to the remote server. host Address of the remote server. path Path on the remote server, including any query string. The following options are also supported: url The full URL when passing options to the driver explicitly. readahead The amount of data to read ahead with each range request to the remote server. This value may optionally have the suffix 'T', 'G', 'M', 'K', 'k' or 'b'. If it does not have a suffix, it will be assumed to be in bytes. The value must be a multi- ple of 512 bytes. It defaults to 256k. sslverify Whether to verify the remote server's certificate when con- necting over SSL. It can have the value 'on' or 'off'. It de- faults to 'on'. cookie Send this cookie (it can also be a list of cookies separated by ';') with each outgoing request. Only supported when using protocols such as HTTP which support cookies, otherwise ig- nored. timeout Set the timeout in seconds of the CURL connection. This time- out is the time that CURL waits for a response from the re- mote server to get the size of the image to be downloaded. If not set, the default timeout of 5 seconds is used. force-range Don't issue a HEAD HTTP request to discover if the http server server supports range requests and rely only on GET requests. This is especially useful for S3 presigned URLs where HEAD requests are unauthorized. It defaults to 'false'. Note that when passing options to qemu explicitly, driver is the value of <protocol>. Example: boot from a remote Fedora 20 live ISO image qemu-system-x86_64 --drive media=cdrom,file=https://archives.fedoraproject.org/pub/archive/fedora/linux/releases/20/Live/x86_64/Fedora-Live-Desktop-x86_64-20-1.iso,readonly qemu-system-x86_64 --drive media=cdrom,file.driver=http,file.url=http://archives.fedoraproject.org/pub/fedora/linux/releases/20/Live/x86_64/Fedora-Live-Desktop-x86_64-20-1.iso,readonly Example: boot from a remote Fedora 20 cloud image using a local overlay for writes, copy-on-read, and a readahead of 64k qemu-img create -f qcow2 -o backing_file='json:{"file.driver":"http",, "file.url":"http://archives.fedoraproject.org/pub/archive/fedora/linux/releases/20/Images/x86_64/Fedora-x86_64-20-20131211.1-sda.qcow2",, "file.readahead":"64k"}' /tmp/Fedora-x86_64-20-20131211.1-sda.qcow2 qemu-system-x86_64 -drive file=/tmp/Fedora-x86_64-20-20131211.1-sda.qcow2,copy-on-read=on Example: boot from an image stored on a VMware vSphere server with a self-signed certificate using a local overlay for writes, a reada- head of 64k and a timeout of 10 seconds. qemu-img create -f qcow2 -o backing_file='json:{"file.driver":"https",, "file.url":"https://user:password@vsphere.example.com/folder/test/test-flat.vmdk?dcPath=Datacenter&dsName=datastore1",, "file.sslverify":"off",, "file.readahead":"64k",, "file.timeout":10}' /tmp/test.qcow2 qemu-system-x86_64 -drive file=/tmp/test.qcow2 SEE ALSO The HTML documentation of QEMU for more precise information and Linux user mode emulator invocation. AUTHOR Fabrice Bellard COPYRIGHT 2026, The QEMU Project Developers 11.0.2 Jul 30, 2026 QEMU(1)
NAME | SYNOPSIS | DESCRIPTION | OPTIONS | MULTIPLEXER KEYS | MULTIPLEXER KEYS | NOTES | SEE ALSO | AUTHOR | COPYRIGHT
Want to link to this manual page? Use this URL:
<https://man.freebsd.org/cgi/man.cgi?query=qemu&sektion=1&manpath=FreeBSD+15.1-RELEASE+and+Ports.quarterly>