FreeBSD Manual Pages
ZFS(8) FreeBSD System Manager's Manual ZFS(8) NAME zfs -- configures ZFS file systems SYNOPSIS zfs [-?] zfs create [-pu] [-o property=value]... filesystem zfs create [-ps] [-b blocksize] [-o property=value]... -V size volume zfs destroy [-fnpRrv] filesystem|volume zfs destroy [-dnpRrv] filesystem|volume@snap[%snap][,snap[%snap]][,...] zfs destroy filesystem|volume#bookmark zfs snapshot|snap [-r] [-o property=value]... filesystem@snapname|volume@snapname filesystem@snapname|volume@snapname... zfs rollback [-rRf] snapshot zfs clone [-p] [-o property=value]... snapshot filesystem|volume zfs promote clone-filesystem zfs rename [-f] filesystem|volume|snapshot filesystem|volume|snapshot zfs rename [-f] -p filesystem|volume filesystem|volume zfs rename -r snapshot snapshot zfs rename -u [-p] filesystem filesystem zfs list [-r|-d depth] [-Hp] [-o property[,property]...] [-t type[,type]...] [-s property]... [-S property]... filesystem|volume|snapshot |bookmark... zfs remap filesystem|volume zfs set property=value [property=value]... filesystem|volume|snapshot... zfs get [-r|-d depth] [-Hp] [-o all | field[,field]...] [-t type[, type]...] [-s source[,source]...] all | property[,property]... filesystem|volume|snapshot... zfs inherit [-rS] property filesystem|volume|snapshot... zfs upgrade [-v] zfs upgrade [-r] [-V version] -a | filesystem zfs userspace [-Hinp] [-o field[,field]...] [-s field]... [-S field]... [-t type[,type]...] filesystem|snapshot zfs groupspace [-Hinp] [-o field[,field]...] [-s field]... [-S field]... [-t type[,type]...] filesystem|snapshot zfs mount zfs mount [-vO] [-o property[,property]...] -a | filesystem zfs unmount|umount [-f] -a | filesystem|mountpoint zfs share -a | filesystem zfs unshare -a | filesystem|mountpoint zfs bookmark snapshot bookmark zfs send [-DLPRVcenpv] [-i snapshot | -I snapshot] snapshot zfs send [-LPcenv] [-i snapshot|bookmark] filesystem|volume|snapshot zfs send [-PVenv] -t receive_resume_token zfs receive|recv [-vnsFu] [-o origin=snapshot] filesystem|volume|snapshot zfs receive|recv [-vnsFu] [-d | -e] [-o origin=snapshot] filesystem zfs receive|recv -A filesystem|volume zfs allow filesystem|volume zfs allow [-ldug] user|group[,user|group]... perm|@setname[,perm|@setname]... filesystem|volume zfs allow [-ld] -e|everyone perm|@setname[,perm|@setname]... filesystem|volume zfs allow -c perm|@setname[,perm|@setname]... filesystem|volume zfs allow -s @setname perm|@setname[,perm|@setname]... filesystem|volume zfs unallow [-rldug] user|group[,user|group]... [perm|@setname[,perm|@setname]...] filesystem|volume zfs unallow [-rld] -e|everyone [perm|@setname[,perm|@setname]...] filesystem|volume zfs unallow [-r] -c [perm|@setname[,perm|@setname]...] filesystem|volume zfs unallow [-r] -s @setname [perm|@setname[,perm|@setname]...] filesystem|volume zfs hold [-r] tag snapshot... zfs holds [-Hp] [-r|-d depth] filesystem|volume|snapshot... zfs release [-r] tag snapshot... zfs diff [-FHt] snapshot [snapshot|filesystem] zfs program [-jn] [-t timeout] [-m memory_limit] pool script [arg1 ...] zfs jail jailid|jailname filesystem zfs unjail jailid|jailname filesystem DESCRIPTION The zfs command configures ZFS datasets within a ZFS storage pool, as de- scribed in zpool(8). A dataset is identified by a unique path within the ZFS namespace. For example: pool/{filesystem,volume,snapshot} where the maximum length of a dataset name is MAXNAMELEN (256 bytes) and the maximum amount of nesting allowed in a path is 50 levels deep. A dataset can be one of the following: file system A ZFS dataset of type filesystem can be mounted within the standard system namespace and behaves like other file sys- tems. While ZFS file systems are designed to be POSIX com- pliant, known issues exist that prevent compliance in some cases. Applications that depend on standards conformance might fail due to nonstandard behavior when checking file system free space. volume A logical volume exported as a raw or block device. This type of dataset should only be used under special circum- stances. File systems are typically used in most environ- ments. snapshot A read-only version of a file system or volume at a given point in time. It is specified as filesystem@name or volume@name. ZFS File System Hierarchy A ZFS storage pool is a logical collection of devices that provide space for datasets. A storage pool is also the root of the ZFS file system hi- erarchy. The root of the pool can be accessed as a file system, such as mounting and unmounting, taking snapshots, and setting properties. The physical storage characteristics, however, are managed by the zpool(8) command. See zpool(8) for more information on creating and administering pools. Snapshots A snapshot is a read-only copy of a file system or volume. Snapshots can be created extremely quickly, and initially consume no additional space within the pool. As data within the active dataset changes, the snapshot consumes more data than would otherwise be shared with the active dataset. Snapshots can have arbitrary names. Snapshots of volumes can be cloned or rolled back, but cannot be accessed independently. File system snapshots can be accessed under the .zfs/snapshot directory in the root of the file system. Snapshots are automatically mounted on demand and may be unmounted at regular intervals. The visibility of the .zfs directory can be controlled by the snapdir property. Clones A clone is a writable volume or file system whose initial contents are the same as another dataset. As with snapshots, creating a clone is nearly instantaneous, and initially consumes no additional space. Clones can only be created from a snapshot. When a snapshot is cloned, it creates an implicit dependency between the parent and child. Even though the clone is created somewhere else in the dataset hierarchy, the origi- nal snapshot cannot be destroyed as long as a clone exists. The origin property exposes this dependency, and the destroy command lists any such dependencies, if they exist. The clone parent-child dependency relationship can be reversed by using the promote subcommand. This causes the "origin" file system to become a clone of the specified file system, which makes it possible to destroy the file system that the clone was created from. Mount Points Creating a ZFS file system is a simple operation, so the number of file systems per system is likely to be numerous. To cope with this, ZFS auto- matically manages mounting and unmounting file systems without the need to edit the /etc/fstab file. All automatically managed file systems are mounted by ZFS at boot time. By default, file systems are mounted under /path, where path is the name of the file system in the ZFS namespace. Directories are created and de- stroyed as needed. A file system can also have a mount point set in the mountpoint property. This directory is created as needed, and ZFS automatically mounts the file system when the "zfs mount -a" command is invoked (without editing /etc/fstab). The mountpoint property can be inherited, so if pool/home has a mount point of /home, then pool/home/user automatically inherits a mount point of /home/user. A file system mountpoint property of none prevents the file system from being mounted. If needed, ZFS file systems can also be managed with traditional tools (mount(8), umount(8), fstab(5)). If a file system's mount point is set to legacy, ZFS makes no attempt to manage the file system, and the admin- istrator is responsible for mounting and unmounting the file system. Jails A ZFS dataset can be attached to a jail by using the "zfs jail" subcom- mand. You cannot attach a dataset to one jail and the children of the same dataset to another jail. You can also not attach the root file sys- tem of the jail or any dataset which needs to be mounted before the zfs rc script is run inside the jail, as it would be attached unmounted until it is mounted from the rc script inside the jail. To allow management of the dataset from within a jail, the jailed property has to be set and the jail needs access to the /dev/zfs device. The quota property cannot be changed from within a jail. See jail(8) for information on how to allow mounting ZFS datasets from within a jail. A ZFS dataset can be detached from a jail using the "zfs unjail" subcom- mand. After a dataset is attached to a jail and the jailed property is set, a jailed file system cannot be mounted outside the jail, since the jail ad- ministrator might have set the mount point to an unacceptable value. Deduplication Deduplication is the process for removing redundant data at the block- level, reducing the total amount of data stored. If a file system has the dedup property enabled, duplicate data blocks are removed synchronously. The result is that only unique data is stored and common components are shared among files. Native Properties Properties are divided into two types, native properties and user-defined (or "user") properties. Native properties either export internal statis- tics or control ZFS behavior. In addition, native properties are either editable or read-only. User properties have no effect on ZFS behavior, but you can use them to annotate datasets in a way that is meaningful in your environment. For more information about user properties, see the "User Properties" section, below. Every dataset has a set of properties that export statistics about the dataset as well as control various behaviors. Properties are inherited from the parent unless overridden by the child. Some properties apply only to certain types of datasets (file systems, volumes, or snapshots). The values of numeric properties can be specified using human-readable suffixes (for example, k, KB, M, Gb, and so forth, up to Z for zettabyte). The following are all valid (and equal) specifications: 1536M, 1.5g, 1.50GB The values of non-numeric properties are case sensitive and must be low- ercase, except for mountpoint, sharenfs, and sharesmb. The following native properties consist of read-only statistics about the dataset. These properties can be neither set, nor inherited. Native prop- erties apply to all dataset types unless otherwise noted. available The amount of space available to the dataset and all its children, assuming that there is no other activity in the pool. Because space is shared within a pool, availability can be limited by any number of factors, including physical pool size, quotas, reservations, or other datasets within the pool. This property can also be referred to by its shortened column name, avail. compressratio For non-snapshots, the compression ratio achieved for the used space of this dataset, expressed as a multiplier. The used property in- cludes descendant datasets, and, for clones, does not include the space shared with the origin snapshot. For snapshots, the compressratio is the same as the refcompressratio property. Compres- sion can be turned on by running: "zfs set compression=on dataset" The default value is off. createtxg The transaction group (txg) in which the dataset was created. Book- marks have the same createtxg as the snapshot they are initially tied to. This property is suitable for ordering a list of snapshots, e.g. for incremental send and receive. creation The time this dataset was created. clones For snapshots, this property is a comma-separated list of filesystems or volumes which are clones of this snapshot. The clones' origin property is this snapshot. If the clones property is not empty, then this snapshot can not be destroyed (even with the -r or -f options). defer_destroy This property is on if the snapshot has been marked for deferred de- stroy by using the "zfs destroy -d" command. Otherwise, the property is off. filesystem_count The total number of filesystems and volumes that exist under this lo- cation in the dataset tree. This value is only available when a filesystem_limit has been set somewhere in the tree under which the dataset resides. guid The 64 bit GUID of this dataset or bookmark which does not change over its entire lifetime. When a snapshot is sent to another pool, the received snapshot has the same GUID. Thus, the guid is suitable to identify a snapshot across pools. logicalreferenced The amount of space that is "logically" accessible by this dataset. See the referenced property. The logical space ignores the effect of the compression and copies properties, giving a quantity closer to the amount of data that applications see. However, it does include space consumed by metadata. This property can also be referred to by its shortened column name, lrefer. logicalused The amount of space that is "logically" consumed by this dataset and all its descendents. See the used property. The logical space ig- nores the effect of the compression and copies properties, giving a quantity closer to the amount of data that applications see. This property can also be referred to by its shortened column name, lused. mounted For file systems, indicates whether the file system is currently mounted. This property can be either yes or no. origin For cloned file systems or volumes, the snapshot from which the clone was created. See also the clones property. receive_resume_token For filesystems or volumes which have saved partially-completed state from zfs receive -s, this opaque token can be provided to zfs send -t to resume and complete the zfs receive. referenced The amount of data that is accessible by this dataset, which may or may not be shared with other datasets in the pool. When a snapshot or clone is created, it initially references the same amount of space as the file system or snapshot it was created from, since its contents are identical. This property can also be referred to by its shortened column name, refer. refcompressratio The compression ratio achieved for the referenced space of this dataset, expressed as a multiplier. See also the compressratio prop- erty. snapshot_count The total number of snapshots that exist under this location in the dataset tree. This value is only available when a snapshot_limit has been set somewhere in the tree under which the dataset resides. type The type of dataset: filesystem, volume, or snapshot. used The amount of space consumed by this dataset and all its descendents. This is the value that is checked against this dataset's quota and reservation. The space used does not include this dataset's reserva- tion, but does take into account the reservations of any descendent datasets. The amount of space that a dataset consumes from its par- ent, as well as the amount of space that are freed if this dataset is recursively destroyed, is the greater of its space used and its reservation. When snapshots (see the "Snapshots" section) are created, their space is initially shared between the snapshot and the file system, and possibly with previous snapshots. As the file system changes, space that was previously shared becomes unique to the snapshot, and counted in the snapshot's space used. Additionally, deleting snap- shots can increase the amount of space unique to (and used by) other snapshots. The amount of space used, available, or referenced does not take into account pending changes. Pending changes are generally accounted for within a few seconds. Committing a change to a disk using fsync(2) or O_SYNC does not necessarily guarantee that the space usage informa- tion is updated immediately. usedby* The usedby* properties decompose the used properties into the various reasons that space is used. Specifically, used = usedbysnapshots + usedbydataset + usedbychildren + usedbyrefreservation. These proper- ties are only available for datasets created with ZFS pool version 13 pools and higher. usedbysnapshots The amount of space consumed by snapshots of this dataset. In partic- ular, it is the amount of space that would be freed if all of this dataset's snapshots were destroyed. Note that this is not simply the sum of the snapshots' used properties because space can be shared by multiple snapshots. usedbydataset The amount of space used by this dataset itself, which would be freed if the dataset were destroyed (after first removing any refreservation and destroying any necessary snapshots or descen- dents). usedbychildren The amount of space used by children of this dataset, which would be freed if all the dataset's children were destroyed. usedbyrefreservation The amount of space used by a refreservation set on this dataset, which would be freed if the refreservation was removed. userused@user The amount of space consumed by the specified user in this dataset. Space is charged to the owner of each file, as displayed by "ls -l". The amount of space charged is displayed by "du" and "ls -s". See the "zfs userspace" subcommand for more information. Unprivileged users can access only their own space usage. The root user, or a user who has been granted the userused privilege with "zfs allow", can access everyone's usage. The userused@... properties are not displayed by "zfs get all". The user's name must be appended after the @ symbol, using one of the following forms: o POSIX name (for example, joe) o POSIX numeric ID (for example, 1001) userrefs This property is set to the number of user holds on this snapshot. User holds are set by using the "zfs hold" command. groupused@group The amount of space consumed by the specified group in this dataset. Space is charged to the group of each file, as displayed by ls -l. See the userused@user property for more information. Unprivileged users can only access their own groups' space usage. The root user, or a user who has been granted the groupused privilege with "zfs allow", can access all groups' usage. volblocksize=blocksize For volumes, specifies the block size of the volume. The blocksize cannot be changed once the volume has been written, so it should be set at volume creation time. The default blocksize for volumes is 8 Kbytes. Any power of 2 from 512 bytes to 128 Kbytes is valid. This property can also be referred to by its shortened column name, volblock. written The amount of referenced space written to this dataset since the pre- vious snapshot. written@snapshot The amount of referenced space written to this dataset since the specified snapshot. This is the space that is referenced by this dataset but was not referenced by the specified snapshot. The snapshot may be specified as a short snapshot name (just the part after the @), in which case it will be interpreted as a snapshot in the same filesystem as this dataset. The snapshot may be a full snap- shot name (filesystem@snapshot), which for clones may be a snapshot in the origin's filesystem (or the origin of the origin's filesystem, etc). The following native properties can be used to change the behavior of a ZFS dataset. aclinherit=discard | noallow | restricted | passthrough | passthrough-x Controls how ACL entries are inherited when files and directories are created. A file system with an aclinherit property of discard does not inherit any ACL entries. A file system with an aclinherit prop- erty value of noallow only inherits inheritable ACL entries that specify "deny" permissions. The property value restricted (the de- fault) removes the write_acl and write_owner permissions when the ACL entry is inherited. A file system with an aclinherit property value of passthrough inherits all inheritable ACL entries without any modi- fications made to the ACL entries when they are inherited. A file system with an aclinherit property value of passthrough-x has the same meaning as passthrough, except that the owner@, group@, and everyone@ ACEs inherit the execute permission only if the file cre- ation mode also requests the execute bit. When the property value is set to passthrough, files are created with a mode determined by the inheritable ACEs. If no inheritable ACEs ex- ist that affect the mode, then the mode is set in accordance to the requested mode from the application. aclmode=discard | groupmask | passthrough | restricted Controls how an ACL is modified during chmod(2). A file system with an aclmode property of discard (the default) deletes all ACL entries that do not represent the mode of the file. An aclmode property of groupmask reduces permissions granted in all ALLOW entries found in the ACL such that they are no greater than the group permissions specified by chmod(2). A file system with an aclmode property of passthrough indicates that no changes are made to the ACL other than creating or updating the necessary ACL entries to represent the new mode of the file or directory. An aclmode property of restricted will cause the chmod(2) operation to return an error when used on any file or directory which has a non-trivial ACL whose entries can not be represented by a mode. chmod(2) is required to change the set user ID, set group ID, or sticky bits on a file or directory, as they do not have equivalent ACL entries. In order to use chmod(2) on a file or directory with a non-trivial ACL when aclmode is set to restricted, you must first remove all ACL entries which do not repre- sent the current mode. atime=on | off Controls whether the access time for files is updated when they are read. Turning this property off avoids producing write traffic when reading files and can result in significant performance gains, though it might confuse mailers and other similar utilities. The default value is on. canmount=on | off | noauto If this property is set to off, the file system cannot be mounted, and is ignored by "zfs mount -a". Setting this property to off is similar to setting the mountpoint property to none, except that the dataset still has a normal mountpoint property, which can be inher- ited. Setting this property to off allows datasets to be used solely as a mechanism to inherit properties. One example of setting canmount=off is to have two datasets with the same mountpoint, so that the children of both datasets appear in the same directory, but might have different inherited characteristics. When the noauto value is set, a dataset can only be mounted and un- mounted explicitly. The dataset is not mounted automatically when the dataset is created or imported, nor is it mounted by the "zfs mount -a" command or unmounted by the "zfs umount -a" command. This property is not inherited. checksum=on | off | fletcher2 | fletcher4 | sha256 | noparity | sha512 | skein Controls the checksum used to verify data integrity. The default value is on, which automatically selects an appropriate algorithm (currently, fletcher4, but this may change in future releases). The value off disables integrity checking on user data. The value noparity not only disables integrity but also disables maintaining parity for user data. This setting is used internally by a dump de- vice residing on a RAID-Z pool and should not be used by any other dataset. Disabling checksums is NOT a recommended practice. The sha512, and skein checksum algorithms require enabling the appropri- ate features on the pool. Please see zpool-features(7) for more in- formation on these algorithms. Changing this property affects only newly-written data. Salted checksum algorithms (edonr, skein) are currently not supported for any filesystem on the boot pools. compression=on | off | lzjb | gzip | gzip-N | zle | lz4 Controls the compression algorithm used for this dataset. Setting compression to on indicates that the current default compression al- gorithm should be used. The default balances compression and decom- pression speed, with compression ratio and is expected to work well on a wide variety of workloads. Unlike all other settings for this property, on does not select a fixed compression type. As new com- pression algorithms are added to ZFS and enabled on a pool, the de- fault compression algorithm may change. The current default compres- sion algorthm is either lzjb or, if the lz4_compress feature is en- abled, lz4. The lzjb compression algorithm is optimized for perfor- mance while providing decent data compression. Setting compression to on uses the lzjb compression algorithm. The gzip compression algo- rithm uses the same compression as the gzip(1) command. You can spec- ify the gzip level by using the value gzip-N where N is an integer from 1 (fastest) to 9 (best compression ratio). Currently, gzip is equivalent to gzip-6 (which is also the default for gzip(1)). The zle compression algorithm compresses runs of zeros. The lz4 compression algorithm is a high-performance replacement for the lzjb algorithm. It features significantly faster compression and decompression, as well as a moderately higher compression ratio than lzjb, but can only be used on pools with the lz4_compress feature set to enabled. See zpool-features(7) for details on ZFS feature flags and the lz4_compress feature. This property can also be referred to by its shortened column name compress. Changing this property affects only newly-written data. copies=1 | 2 | 3 Controls the number of copies of data stored for this dataset. These copies are in addition to any redundancy provided by the pool, for example, mirroring or RAID-Z. The copies are stored on different disks, if possible. The space used by multiple copies is charged to the associated file and dataset, changing the used property and counting against quotas and reservations. Changing this property only affects newly-written data. Therefore, set this property at file system creation time by using the -o copies=N option. dedup=on | off | verify | sha256[,verify] | sha512[,verify] | skein[,verify] Configures deduplication for a dataset. The default value is off. The default deduplication checksum is sha256 (this may change in the future). When dedup is enabled, the checksum defined here overrides the checksum property. Setting the value to verify has the same ef- fect as the setting sha256,verify. If set to verify, ZFS will do a byte-to-byte comparsion in case of two blocks having the same signature to make sure the block contents are identical. devices=on | off The devices property is currently not supported on FreeBSD. exec=on | off Controls whether processes can be executed from within this file sys- tem. The default value is on. mlslabel=label | none The mlslabel property is currently not supported on FreeBSD. filesystem_limit=count | none Limits the number of filesystems and volumes that can exist under this point in the dataset tree. The limit is not enforced if the user is allowed to change the limit. Setting a filesystem_limit on a descendent of a filesystem that already has a filesystem_limit does not override the ancestor's filesystem_limit, but rather imposes an additional limit. This feature must be enabled to be used (see zpool-features(7)). mountpoint=path | none | legacy Controls the mount point used for this file system. See the "Mount Points" section for more information on how this property is used. When the mountpoint property is changed for a file system, the file system and any children that inherit the mount point are unmounted. If the new value is legacy, then they remain unmounted. Otherwise, they are automatically remounted in the new location if the property was previously legacy or none, or if they were mounted before the property was changed. In addition, any shared file systems are un- shared and shared in the new location. nbmand=on | off The nbmand property is currently not supported on FreeBSD. primarycache=all | none | metadata Controls what is cached in the primary cache (ARC). If this property is set to all, then both user data and metadata is cached. If this property is set to none, then neither user data nor metadata is cached. If this property is set to metadata, then only metadata is cached. The default value is all. quota=size | none Limits the amount of space a dataset and its descendents can consume. This property enforces a hard limit on the amount of space used. This includes all space consumed by descendents, including file systems and snapshots. Setting a quota on a descendent of a dataset that al- ready has a quota does not override the ancestor's quota, but rather imposes an additional limit. Quotas cannot be set on volumes, as the volsize property acts as an implicit quota. snapshot_limit=count | none Limits the number of snapshots that can be created on a dataset and its descendents. Setting a snapshot_limit on a descendent of a dataset that already has a snapshot_limit does not override the an- cestor's snapshot_limit, but rather imposes an additional limit. The limit is not enforced if the user is allowed to change the limit. For example, this means that recursive snapshots taken from the global zone are counted against each delegated dataset within a jail. This feature must be enabled to be used (see zpool-features(7)). userquota@user=size | none Limits the amount of space consumed by the specified user. Similar to the refquota property, the userquota space calculation does not include space that is used by descendent datasets, such as snapshots and clones. User space consumption is identified by the userspace@user property. Enforcement of user quotas may be delayed by several seconds. This delay means that a user might exceed their quota before the system notices that they are over quota and begins to refuse additional writes with the EDQUOT error message. See the userspace subcommand for more information. Unprivileged users can only access their own groups' space usage. The root user, or a user who has been granted the userquota privilege with "zfs allow", can get and set everyone's quota. This property is not available on volumes, on file systems before version 4, or on pools before version 15. The userquota@... proper- ties are not displayed by "zfs get all". The user's name must be ap- pended after the @ symbol, using one of the following forms: o POSIX name (for example, joe) o POSIX numeric ID (for example, 1001) groupquota@group=size | none Limits the amount of space consumed by the specified group. Group space consumption is identified by the userquota@user property. Unprivileged users can access only their own groups' space usage. The root user, or a user who has been granted the groupquota privilege with "zfs allow", can get and set all groups' quotas. readonly=on | off Controls whether this dataset can be modified. The default value is off. recordsize=size Specifies a suggested block size for files in the file system. This property is designed solely for use with database workloads that ac- cess files in fixed-size records. ZFS automatically tunes block sizes according to internal algorithms optimized for typical access patterns. For databases that create very large files but access them in small random chunks, these algorithms may be suboptimal. Specifying a recordsize greater than or equal to the record size of the database can result in significant performance gains. Use of this property for general purpose file systems is strongly discouraged, and may ad- versely affect performance. The size specified must be a power of two greater than or equal to 512 and less than or equal to 128 Kbytes. If the large_blocks fea- ture is enabled on the pool, the size may be up to 1 Mbyte. See zpool-features(7) for details on ZFS feature flags. Changing the file system's recordsize affects only files created af- terward; existing files are unaffected. This property can also be referred to by its shortened column name, recsize. redundant_metadata=all | most Controls what types of metadata are stored redundantly. ZFS stores an extra copy of metadata, so that if a single block is corrupted, the amount of user data lost is limited. This extra copy is in addi- tion to any redundancy provided at the pool level (e.g. by mirroring or RAID-Z), and is in addition to an extra copy specified by the copies property (up to a total of 3 copies). For example if the pool is mirrored, copies=2, and redundant_metadata=most, then ZFS stores 6 copies of most metadata, and 4 copies of data and some metadata. When set to all, ZFS stores an extra copy of all metadata. If a sin- gle on-disk block is corrupt, at worst a single block of user data (which is recordsize bytes long can be lost.) When set to most, ZFS stores an extra copy of most types of metadata. This can improve performance of random writes, because less metadata must be written. In practice, at worst about 100 blocks (of recordsize bytes each) of user data can be lost if a single on-disk block is corrupt. The exact behavior of which metadata blocks are stored redundantly may change in future releases. The default value is all. refquota=size | none Limits the amount of space a dataset can consume. This property en- forces a hard limit on the amount of space used. This hard limit does not include space used by descendents, including file systems and snapshots. refreservation=size | none | auto The minimum amount of space guaranteed to a dataset, not including its descendents. When the amount of space used is below this value, the dataset is treated as if it were taking up the amount of space specified by refreservation. The refreservation reservation is ac- counted for in the parent datasets' space used, and counts against the parent datasets' quotas and reservations. If refreservation is set, a snapshot is only allowed if there is enough free pool space outside of this reservation to accommodate the current number of "referenced" bytes in the dataset. If refreservation is set to auto, a volume is thick provisioned or not sparse. refreservation= auto is only supported on volumes. See volsize in the Native Properties section for more information about sparse volumes. This property can also be referred to by its shortened column name, refreserv. reservation=size | none The minimum amount of space guaranteed to a dataset and its descen- dents. When the amount of space used is below this value, the dataset is treated as if it were taking up the amount of space specified by its reservation. Reservations are accounted for in the parent datasets' space used, and count against the parent datasets' quotas and reservations. This property can also be referred to by its shortened column name, reserv. secondarycache=all | none | metadata Controls what is cached in the secondary cache (L2ARC). If this prop- erty is set to all, then both user data and metadata is cached. If this property is set to none, then neither user data nor metadata is cached. If this property is set to metadata, then only metadata is cached. The default value is all. setuid=on | off Controls whether the set-UID bit is respected for the file system. The default value is on. sharesmb=on | off | opts The sharesmb property currently has no effect on FreeBSD. sharenfs=on | off | opts Controls whether the file system is shared via NFS, and what options are used. A file system with a sharenfs property of off is managed the traditional way via exports(5). Otherwise, the file system is automatically shared and unshared with the "zfs share" and "zfs unshare" commands. If the property is set to on no NFS export options are used. Otherwise, NFS export options are equivalent to the con- tents of this property. The export options may be comma-separated. See exports(5) for a list of valid options. When the sharenfs property is changed for a dataset, the mountd(8) daemon is reloaded. logbias=latency | throughput Provide a hint to ZFS about handling of synchronous requests in this dataset. If logbias is set to latency (the default), ZFS will use pool log devices (if configured) to handle the requests at low la- tency. If logbias is set to throughput, ZFS will not use configured pool log devices. ZFS will instead optimize synchronous operations for global pool throughput and efficient use of resources. snapdir=hidden | visible Controls whether the .zfs directory is hidden or visible in the root of the file system as discussed in the "Snapshots" section. The de- fault value is hidden. sync=standard | always | disabled Controls the behavior of synchronous requests (e.g. fsync(2), O_DSYNC). This property accepts the following values: standard This is the POSIX specified behavior of ensuring all synchronous requests are written to stable storage and all devices are flushed to ensure data is not cached by device controllers (this is the default). always All file system transactions are written and flushed before their system calls return. This has a large per- formance penalty. disabled Disables synchronous requests. File system transactions are only committed to stable storage periodically. This option will give the highest performance. However, it is very dangerous as ZFS would be ignoring the synchro- nous transaction demands of applications such as data- bases or NFS. Administrators should only use this op- tion when the risks are understood. volsize=size For volumes, specifies the logical size of the volume. By default, creating a volume establishes a reservation of equal size. For stor- age pools with a version number of 9 or higher, a refreservation is set instead. Any changes to volsize are reflected in an equivalent change to the reservation (or refreservation). The volsize can only be set to a multiple of volblocksize, and cannot be zero. The reservation is kept equal to the volume's logical size to prevent unexpected behavior for consumers. Without the reservation, the vol- ume could run out of space, resulting in undefined behavior or data corruption, depending on how the volume is used. These effects can also occur when the volume size is changed while it is in use (par- ticularly when shrinking the size). Extreme care should be used when adjusting the volume size. Though not recommended, a "sparse volume" (also known as "thin provi- sioned") can be created by specifying the -s option to the "zfs create -V" command, or by changing the value of the refreservation property, or reservation property on pool version 8 or earlier ) after the volume has been created. A "sparse volume" is a volume where the value of refreservation is less then the size of the volume plus the space required to store its metadata. Consequently, writes to a sparse volume can fail with ENOSPC when the pool is low on space. For a sparse volume, changes to volsize are not reflected in the refreservation. A volume that is not sparse is said to be "thick provisioned". A sparse volume can become thick provisioned by set- ting refreservation to auto. volmode=default | geom | dev | none This property specifies how volumes should be exposed to the OS. Setting it to geom exposes volumes as geom(4) providers, providing maximal functionality. Setting it to dev exposes volumes only as cdev device in devfs. Such volumes can be accessed only as raw disk device files, i.e. they can not be partitioned, mounted, participate in RAIDs, etc, but they are faster, and in some use scenarios with untrusted consumer, such as NAS or VM storage, can be more safe. Volumes with property set to none are not exposed outside ZFS, but can be snapshoted, cloned, replicated, etc, that can be suitable for backup purposes. Value default means that volumes exposition is con- trolled by system-wide sysctl/tunable vfs.zfs.vol.mode, where geom, dev and none are encoded as 1, 2 and 3 respectively. The default values is geom. This property can be changed any time, but so far it is processed only during volume creation and pool import. vscan=off | on The vscan property is currently not supported on FreeBSD. xattr=off | on The xattr property is currently not supported on FreeBSD. jailed=off | on Controls whether the dataset is managed from a jail. See the "Jails" section for more information. The default value is off. The following three properties cannot be changed after the file system is created, and therefore, should be set when the file system is created. If the properties are not set with the "zfs create" or zpool create com- mands, these properties are inherited from the parent dataset. If the parent dataset lacks these properties due to having been created prior to these features being supported, the new file system will have the default values for these properties. casesensitivity=sensitive | insensitive | mixed Indicates whether the file name matching algorithm used by the file system should be case-sensitive, case-insensitive, or allow a com- bination of both styles of matching. The default value for the casesensitivity property is sensitive. Traditionally, UNIX and POSIX file systems have case-sensitive file names. The mixed value for the casesensitivity property indicates that the file system can support requests for both case-sensitive and case- insensitive matching behavior. normalization=none | formC | formD | formKC | formKD Indicates whether the file system should perform a unicode normal- ization of file names whenever two file names are compared, and which normalization algorithm should be used. File names are always stored unmodified, names are normalized as part of any comparison process. If this property is set to a legal value other than none, and the utf8only property was left unspecified, the utf8only prop- erty is automatically set to on. The default value of the normalization property is none. This property cannot be changed after the file system is created. utf8only=on | off Indicates whether the file system should reject file names that in- clude characters that are not present in the UTF-8 character code set. If this property is explicitly set to off, the normalization property must either not be explicitly set or be set to none. The default value for the utf8only property is off. This property can- not be changed after the file system is created. The casesensitivity, normalization, and utf8only properties are also new permissions that can be assigned to non-privileged users by using the ZFS delegated administration feature. Temporary Mount Point Properties When a file system is mounted, either through mount(8) for legacy mounts or the "zfs mount" command for normal file systems, its mount options are set according to its properties. The correlation between properties and mount options is as follows: PROPERTY MOUNT OPTION atime atime/noatime exec exec/noexec readonly ro/rw setuid suid/nosuid In addition, these options can be set on a per-mount basis using the -o option, without affecting the property that is stored on disk. The values specified on the command line override the values stored in the dataset. These properties are reported as "temporary" by the "zfs get" command. If the properties are changed while the dataset is mounted, the new setting overrides any temporary settings. User Properties In addition to the standard native properties, ZFS supports arbitrary user properties. User properties have no effect on ZFS behavior, but ap- plications or administrators can use them to annotate datasets (file sys- tems, volumes, and snapshots). User property names must contain a colon (:) character to distinguish them from native properties. They may contain lowercase letters, numbers, and the following punctuation characters: colon (:), dash (-), period (.) and underscore (_). The expected convention is that the property name is divided into two portions such as module:property, but this namespace is not enforced by ZFS. User property names can be at most 256 characters, and cannot begin with a dash (-). When making programmatic use of user properties, it is strongly suggested to use a reversed DNS domain name for the module component of property names to reduce the chance that two independently-developed packages use the same property name for different purposes. Property names beginning with com.sun are reserved for use by Sun Microsystems. The values of user properties are arbitrary strings, are always inher- ited, and are never validated. All of the commands that operate on prop- erties ("zfs list", "zfs get", "zfs set" and so forth) can be used to ma- nipulate both native properties and user properties. Use the "zfs inherit" command to clear a user property. If the property is not defined in any parent dataset, it is removed entirely. Property values are lim- ited to 1024 characters. SUBCOMMANDS All subcommands that modify state are logged persistently to the pool in their original form. Displays a help message. Creates a new ZFS file system. The file system is automatically mounted according to the mountpoint property inherited from the parent. -p Creates all the non-existing parent datasets. Datasets created in this manner are automatically mounted according to the mountpoint property inherited from their parent. Any property specified on the command line using the -o option is ignored. If the target filesystem already exists, the operation completes successfully. -u Newly created file system is not mounted. -o property=value Sets the specified property as if the command "zfs set property=value" was invoked at the same time the dataset was cre- ated. Any editable ZFS property can also be set at creation time. Multiple -o options can be specified. An error results if the same property is specified in multiple -o options. Creates a volume of the given size. The volume is exported as a block de- vice in /dev/zvol/path, where path is the name of the volume in the ZFS namespace. The size represents the logical size as exported by the de- vice. By default, a reservation of equal size is created. size is automatically rounded up to the nearest 128 Kbytes to ensure that the volume has an integral number of blocks regardless of blocksize. -p Creates all the non-existing parent datasets. Datasets created in this manner are automatically mounted according to the mountpoint property inherited from their parent. Any property specified on the command line using the -o option is ignored. If the target filesystem already exists, the operation completes successfully. -s Creates a sparse volume with no reservation. See volsize in the "Native Properties" section for more information about sparse volumes. -b blocksize Equivalent to -o volblocksize=blocksize. If this option is spec- ified in conjunction with -o volblocksize, the resulting behavior is undefined. -o property=value Sets the specified property as if the "zfs set property=value" command was invoked at the same time the dataset was created. Any editable ZFS property can also be set at creation time. Multiple -o options can be specified. An error results if the same prop- erty is specified in multiple -o options. Destroys the given dataset. By default, the command unshares any file systems that are currently shared, unmounts any file systems that are currently mounted, and refuses to destroy a dataset that has active de- pendents (children or clones). -r Recursively destroy all children. -R Recursively destroy all dependents, including cloned file systems outside the target hierarchy. -f Force an unmount of any file systems using the "zfs unmount -f" command. This option has no effect on non-file systems or un- mounted file systems. -n Do a dry-run ("No-op") deletion. No data will be deleted. This is useful in conjunction with the -v or -p flags to determine what data would be deleted. -p Print machine-parsable verbose information about the deleted data. -v Print verbose information about the deleted data. Extreme care should be taken when applying either the -r or the -R op- tions, as they can destroy large portions of a pool and cause unexpected behavior for mounted file systems in use. The given snapshots are destroyed immediately if and only if the "zfs destroy" command without the -d option would have destroyed it. Such im- mediate destruction would occur, for example, if the snapshot had no clones and the user-initiated reference count were zero. If a snapshot does not qualify for immediate destruction, it is marked for deferred deletion. In this state, it exists as a usable, visible snapshot until both of the preconditions listed above are met, at which point it is destroyed. An inclusive range of snapshots may be specified by separating the first and last snapshots with a percent sign (%). The first and/or last snap- shots may be left blank, in which case the filesystem's oldest or newest snapshot will be implied. Multiple snapshots (or ranges of snapshots) of the same filesystem or volume may be specified in a comma-separated list of snapshots. Only the snapshot's short name (the part after the @) should be specified when us- ing a range or comma-separated list to identify multiple snapshots. -r Destroy (or mark for deferred deletion) all snapshots with this name in descendent file systems. -R Recursively destroy all clones of these snapshots, including the clones, snapshots, and children. If this flag is specified, the -d flag will have no effect. -n Do a dry-run ("No-op") deletion. No data will be deleted. This is useful in conjunction with the -v or -p flags to determine what data would be deleted. -p Print machine-parsable verbose information about the deleted data. -v Print verbose information about the deleted data. -d Defer snapshot deletion. Extreme care should be taken when applying either the -r or the -R op- tions, as they can destroy large portions of a pool and cause unexpected behavior for mounted file systems in use. The given bookmark is destroyed. Creates snapshots with the given names. All previous modifications by successful system calls to the file system are part of the snapshots. Snapshots are taken atomically, so that all snapshots correspond to the same moment in time. See the "Snapshots" section for details. -r Recursively create snapshots of all descendent datasets -o property=value Sets the specified property; see "zfs create" for details. Roll back the given dataset to a previous snapshot. When a dataset is rolled back, all data that has changed since the snapshot is discarded, and the dataset reverts to the state at the time of the snapshot. By de- fault, the command refuses to roll back to a snapshot other than the most recent one. In order to do so, all intermediate snapshots and bookmarks must be destroyed by specifying the -r option. The -rR options do not recursively destroy the child snapshots of a re- cursive snapshot. Only direct snapshots of the specified filesystem are destroyed by either of these options. To completely roll back a recur- sive snapshot, you must rollback the individual child snapshots. -r Destroy any snapshots and bookmarks more recent than the one specified. -R Destroy any more recent snapshots and bookmarks, as well as any clones of those snapshots. -f Used with the -R option to force an unmount of any clone file systems that are to be destroyed. Creates a clone of the given snapshot. See the "Clones" section for de- tails. The target dataset can be located anywhere in the ZFS hierarchy, and is created as the same type as the original. -p Creates all the non-existing parent datasets. Datasets created in this manner are automatically mounted according to the mountpoint property inherited from their parent. If the target filesystem or volume already exists, the operation completes successfully. -o property=value Sets the specified property; see "zfs create" for details. Promotes a clone file system to no longer be dependent on its "origin" snapshot. This makes it possible to destroy the file system that the clone was created from. The clone parent-child dependency relationship is reversed, so that the origin file system becomes a clone of the specified file system. The snapshot that was cloned, and any snapshots previous to this snap- shot, are now owned by the promoted clone. The space they use moves from the origin file system to the promoted clone, so enough space must be available to accommodate these snapshots. No new space is consumed by this operation, but the space accounting is adjusted. The promoted clone must not have any conflicting snapshot names of its own. The rename sub- command can be used to rename any conflicting snapshots. Renames the given dataset. The new target can be located anywhere in the ZFS hierarchy, with the exception of snapshots. Snapshots can only be re- named within the parent file system or volume. When renaming a snapshot, the parent file system of the snapshot does not need to be specified as part of the second argument. Renamed file systems can inherit new mount points, in which case they are unmounted and remounted at the new mount point. -p Creates all the nonexistent parent datasets. Datasets created in this manner are automatically mounted according to the mountpoint property inherited from their parent. -u Do not remount file systems during rename. If a file system's mountpoint property is set to legacy or none, file system is not unmounted even if this option is not given. -f Force unmount any filesystems that need to be unmounted in the process. This flag has no effect if used together with the -u flag. Recursively rename the snapshots of all descendent datasets. Snapshots are the only dataset that can be renamed recursively. Lists the property information for the given datasets in tabular form. If specified, you can list property information by the absolute pathname or the relative pathname. By default, all file systems and volumes are dis- played. Snapshots are displayed if the listsnaps property is on (the de- fault is off). The following fields are displayed, name, used, available, referenced, mountpoint. -r Recursively display any children of the dataset on the command line. -d depth Recursively display any children of the dataset, limiting the re- cursion to depth. A depth of 1 will display only the dataset and its direct children. -H Used for scripting mode. Do not print headers and separate fields by a single tab instead of arbitrary white space. -p Display numbers in parsable (exact) values. -o property[,property]... A comma-separated list of properties to display. The property must be: o One of the properties described in the "Native Properties" section o A user property o The value name to display the dataset name o The value space to display space usage properties on file systems and volumes. This is a shortcut for specifying -o name,avail,used,usedsnap,usedds,usedrefreserv,usedchild -t filesystem,volume syntax. -t type[,type]... A comma-separated list of types to display, where type is one of filesystem, snapshot, snap, volume, bookmark, or all. For exam- ple, specifying -t snapshot displays only snapshots. -s property A property for sorting the output by column in ascending order based on the value of the property. The property must be one of the properties described in the "Properties" section, or the spe- cial value name to sort by the dataset name. Multiple properties can be specified at one time using multiple -s property options. Multiple -s options are evaluated from left to right in decreas- ing order of importance. The following is a list of sorting criteria: o Numeric types sort in numeric order. o String types sort in alphabetical order. o Types inappropriate for a row sort that row to the literal bottom, regardless of the specified ordering. o If no sorting options are specified the existing behavior of "zfs list" is preserved. -S property Same as the -s option, but sorts by property in descending order. Sets the property or list of properties to the given value(s) for each dataset. Only some properties can be edited. See the "Properties" sec- tion for more information on what properties can be set and acceptable values. Numeric values can be specified as exact values, or in a human- readable form with a suffix of B, K, M, G, T, P, E, Z (for bytes, kilo- bytes, megabytes, gigabytes, terabytes, petabytes, exabytes, or zettabytes, respectively). User properties can be set on snapshots. For more information, see the "User Properties" section. Displays properties for the given datasets. If no datasets are specified, then the command displays properties for all datasets on the system. For each property, the following columns are displayed: name Dataset name property Property name value Property value source Property source. Can either be local, default, temporary, inherited, received, or none (-). All columns except the RECEIVED column are displayed by default. The col- umns to display can be specified by using the -o option. This command takes a comma-separated list of properties as described in the "Native Properties" and "User Properties" sections. The special value all can be used to display all properties that apply to the given dataset's type (filesystem, volume, snapshot, or bookmark). -r Recursively display properties for any children. -d depth Recursively display any children of the dataset, limiting the re- cursion to depth. A depth of 1 will display only the dataset and its direct children. -H Display output in a form more easily parsed by scripts. Any head- ers are omitted, and fields are explicitly separated by a single tab instead of an arbitrary amount of space. -p Display numbers in parsable (exact) values. -o all | field[,field]... A comma-separated list of columns to display. Supported values are name,property,value,received,source. Default values are name,property,value,source. The keyword all specifies all col- umns. -t type[,type]... A comma-separated list of types to display, where type is one of filesystem, snapshot, volume, or all. For example, specifying -t snapshot displays only snapshots. -s source[,source]... A comma-separated list of sources to display. Those properties coming from a source other than those in this list are ignored. Each source must be one of the following: local,default,inherited,temporary,received,none. The default value is all sources. Clears the specified property, causing it to be inherited from an ances- tor, restored to default if no ancestor has the property set, or with the -S option reverted to the received value if one exists. See the "Properties" section for a listing of default values, and details on which properties can be inherited. -r Recursively inherit the given property for all children. -S Revert the property to the received value if one exists; other- wise operate as if the -S option was not specified. Remap the indirect blocks in the given fileystem or volume so that they no longer reference blocks on previously removed vdevs and we can eventu- ally shrink the size of the indirect mapping objects for the previously removed vdevs. Note that remapping all blocks might not be possible and that references from snapshots will still exist and cannot be remapped. Displays a list of file systems that are not the most recent version. -v Displays ZFS filesystem versions supported by the current soft- ware. The current ZFS filesystem version and all previous sup- ported versions are displayed, along with an explanation of the features provided with each version. Upgrades file systems to a new on-disk version. Once this is done, the file systems will no longer be accessible on systems running older ver- sions of the software. "zfs send" streams generated from new snapshots of these file systems cannot be accessed on systems running older ver- sions of the software. In general, the file system version is independent of the pool version. See zpool(8) for information on the zpool upgrade command. In some cases, the file system version and the pool version are interre- lated and the pool version must be upgraded before the file system ver- sion can be upgraded. -r Upgrade the specified file system and all descendent file sys- tems. -V version Upgrade to the specified version. If the -V flag is not speci- fied, this command upgrades to the most recent version. This op- tion can only be used to increase the version number, and only up to the most recent version supported by this software. -a Upgrade all file systems on all imported pools. filesystem Upgrade the specified file system. Displays space consumed by, and quotas on, each user in the specified filesystem or snapshot. This corresponds to the userused@user and userquota@user properties. -n Print numeric ID instead of user/group name. -H Do not print headers, use tab-delimited output. -p Use exact (parsable) numeric output. -o field[,field]... Display only the specified fields from the following set: type,name,used,quota. The default is to display all fields. -s field Sort output by this field. The -s and -S flags may be specified multiple times to sort first by one field, then by another. The default is -s type -s name. -S field Sort by this field in reverse order. See -s. -t type[,type]... Print only the specified types from the following set: all,posixuser,smbuser,posixgroup,smbgroup. The default is -t posixuser,smbuser. The default can be changed to include group types. -i Translate SID to POSIX ID. This flag currently has no effect on FreeBSD. Displays space consumed by, and quotas on, each group in the specified filesystem or snapshot. This subcommand is identical to "zfs userspace", except that the default types to display are -t posixgroup,smbgroup. Displays all ZFS file systems currently mounted. -f Mounts ZFS file systems. -v Report mount progress. -O Perform an overlay mount. Overlay mounts are not supported on FreeBSD. -o property[,property]... An optional, comma-separated list of mount options to use tempo- rarily for the duration of the mount. See the "Temporary Mount Point Properties" section for details. -a Mount all available ZFS file systems. This command may be exe- cuted on FreeBSD system startup by /etc/rc.d/zfs. For more in- formation, see variable zfs_enable in rc.conf(5). filesystem Mount the specified filesystem. Unmounts currently mounted ZFS file systems. -f Forcefully unmount the file system, even if it is currently in use. -a Unmount all available ZFS file systems. filesystem | mountpoint Unmount the specified filesystem. The command can also be given a path to a ZFS file system mount point on the system. Shares ZFS file systems that have the sharenfs property set. -a Share all ZFS file systems that have the sharenfs property set. This command may be executed on FreeBSD system startup by /etc/rc.d/zfs. For more information, see variable zfs_enable in rc.conf(5). filesystem Share the specified filesystem according to the sharenfs prop- erty. File systems are shared when the sharenfs property is set. Unshares ZFS file systems that have the sharenfs property set. -a Unshares ZFS file systems that have the sharenfs property set. This command may be executed on FreeBSD system shutdown by /etc/rc.d/zfs. For more information, see variable zfs_enable in rc.conf(5). filesystem | mountpoint Unshare the specified filesystem. The command can also be given a path to a ZFS file system shared on the system. Creates a bookmark of the given snapshot. Bookmarks mark the point in time when the snapshot was created, and can be used as the incremental source for a "zfs send" command. This feature must be enabled to be used. See zpool-features(7) for de- tails on ZFS feature flags and the bookmark feature. Creates a stream representation of the last snapshot argument (not part of -i or -I) which is written to standard output. The output can be redi- rected to a file or to a different system (for example, using ssh(1)). By default, a full stream is generated. -i snapshot Generate an incremental stream from the first snapshot (the incremental source) to the second snapshot (the incremental target). The incremental source can be specified as the last component of the snapshot name (the @ character and following) and it is assumed to be from the same file system as the incre- mental target. If the destination is a clone, the source may be the origin snap- shot, which must be fully specified (for example, pool/fs@origin, not just @origin). -I snapshot Generate a stream package that sends all intermediary snapshots from the first snapshot to the second snapshot. For example, -I @a fs@d is similar to -i @a fs@b; -i @b fs@c; -i @c fs@d. The incremental source may be specified as with the -i option. -R, --replicate Generate a replication stream package, which will replicate the specified filesystem, and all descendent file systems, up to the named snapshot. When received, all properties, snapshots, descen- dent file systems, and clones are preserved. If the -i or -I flags are used in conjunction with the -R flag, an incremental replication stream is generated. The current val- ues of properties, and current snapshot and file system names are set when the stream is received. If the -F flag is specified when this stream is received, snapshots and file systems that do not exist on the sending side are destroyed. -D, --dedup Generate a deduplicated stream. Blocks which would have been sent multiple times in the send stream will only be sent once. The receiving system must also support this feature to receive a deduplicated stream. This flag can be used regardless of the dataset's dedup property, but performance will be much better if the filesystem uses a dedup-capable checksum (eg. sha256). -L, --large-block Generate a stream which may contain blocks larger than 128KB. This flag has no effect if the large_blocks pool feature is dis- abled, or if the recordsize property of this filesystem has never been set above 128KB. The receiving system must have the large_blocks pool feature enabled as well. See zpool-features(7) for details on ZFS feature flags and the large_blocks feature. -e, --embed Generate a more compact stream by using WRITE_EMBEDDED records for blocks which are stored more compactly on disk by the embedded_data pool feature. This flag has no effect if the embedded_data feature is disabled. The receiving system must have the embedded_data feature enabled. If the lz4_compress fea- ture is active on the sending system, then the receiving system must have that feature enabled as well. See zpool-features(7) for details on ZFS feature flags and the embedded_data feature. -c, --compressed Generate a more compact stream by using compressed WRITE records for blocks which are compressed on disk and in memory (see the compression property for details). If the lz4_compress feature is active on the sending system, then the receiving system must have that feature enabled as well. If the large_blocks feature is enabled on the sending system but the -L option is not supplied in conjunction with -c then the data will be decompressed before sending so it can be split into smaller block sizes. -p, --props Include the dataset's properties in the stream. This flag is im- plicit when -R is specified. The receiving system must also sup- port this feature. -n, --dryrun Do a dry-run ("No-op") send. Do not generate any actual send data. This is useful in conjunction with the -v or -P flags to determine what data will be sent. In this case, the verbose out- put will be written to standard output (contrast with a non-dry- run, where the stream is written to standard output and the ver- bose output goes to standard error). -P, --parsable Print machine-parsable verbose information about the stream pack- age generated. -v, --verbose Print verbose information about the stream package generated. This information includes a per-second report of how much data has been sent. -V Set the process title to a per-second report of how much data has been sent. The format of the stream is committed. You will be able to receive your streams on future versions of ZFS. Generate a send stream, which may be of a filesystem, and may be incre- mental from a bookmark. If the destination is a filesystem or volume, the pool must be read-only, or the filesystem must not be mounted. When the stream generated from a filesystem or volume is received, the default snapshot name will be (--head--). -i snapshot|bookmark Generate an incremental send stream. The incremental source must be an earlier snapshot in the destination's history. It will commonly be an earlier snapshot in the destination's filesystem, in which case it can be specified as the last component of the name (the # or @ character and following). If the incremental target is a clone, the incremental source can be the origin snapshot, or an earlier snapshot in the origin's filesystem, or the origin's origin, etc. -n, --dryrun Do a dry-run ("No-op") send. Do not generate any actual send data. This is useful in conjunction with the -v or -P flags to determine what data will be sent. In this case, the verbose out- put will be written to standard output (contrast with a non-dry-run, where the stream is written to standard output and the verbose output goes to standard error). -v, --verbose Print verbose information about the stream package generated. This information includes a per-second report of how much data has been sent. -L, --large-block Generate a stream which may contain blocks larger than 128KB. This flag has no effect if the large_blocks pool feature is dis- abled, or if the recordsize property of this filesystem has never been set above 128KB. The receiving system must have the large_blocks pool feature enabled as well. See zpool-features(7) for details on ZFS feature flags and the large_blocks feature. -P, --parsable Print machine-parsable verbose information about the stream pack- age generated. -c, --compressed Generate a more compact stream by using compressed WRITE records for blocks which are compressed on disk and in memory (see the compression property for details). If the lz4_compress feature is active on the sending system, then the receiving system must have that feature enabled as well. If the large_blocks feature is enabled on the sending system but the -L option is not supplied in conjunction with -c then the data will be decompressed before sending so it can be split into smaller block sizes. -e, --embed Generate a more compact stream by using WRITE_EMBEDDED records for blocks which are stored more compactly on disk by the embedded_data pool feature. This flag has no effect if the embedded_data feature is disabled. The receiving system must have the embedded_data feature enabled. If the lz4_compress fea- ture is active on the sending system, then the receiving system must have that feature enabled as well. See zpool-features(7) for details on ZFS feature flags and the embedded_data feature. Creates a send stream which resumes an interrupted receive. The receive_resume_token is the value of this property on the filesystem or volume that was being received into. See the documentation for zfs receive -s for more details. Creates a snapshot whose contents are as specified in the stream provided on standard input. If a full stream is received, then a new file system is created as well. Streams are created using the "zfs send" subcommand, which by default creates a full stream. "zfs recv" can be used as an alias for "zfs receive". If an incremental stream is received, then the destination file system must already exist, and its most recent snapshot must match the incremen- tal stream's source. For zvols, the destination device link is destroyed and recreated, which means the zvol cannot be accessed during the receive operation. When a snapshot replication package stream that is generated by using the "zfs send -R" command is received, any snapshots that do not exist on the sending location are destroyed by using the "zfs destroy -d" command. The name of the snapshot (and file system, if a full stream is received) that this subcommand creates depends on the argument type and the -d or -e option. If the argument is a snapshot name, the specified snapshot is created. If the argument is a file system or volume name, a snapshot with the same name as the sent snapshot is created within the specified filesystem or volume. If the -d or -e option is specified, the snapshot name is deter- mined by appending the sent snapshot's name to the specified filesystem. If the -d option is specified, all but the pool name of the sent snapshot path is appended (for example, b/c@1 appended from sent snapshot a/b/c@1), and if the -e option is specified, only the tail of the sent snapshot path is appended (for example, c@1 appended from sent snapshot a/b/c@1). In the case of -d, any file systems needed to replicate the path of the sent snapshot are created within the specified file system. -d Use the full sent snapshot path without the first element (with- out pool name) to determine the name of the new snapshot as de- scribed in the paragraph above. -e Use only the last element of the sent snapshot path to determine the name of the new snapshot as described in the paragraph above. -u File system that is associated with the received stream is not mounted. -v Print verbose information about the stream and the time required to perform the receive operation. -n Do not actually receive the stream. This can be useful in con- junction with the -v option to verify the name the receive opera- tion would use. -o origin=snapshot Forces the stream to be received as a clone of the given snap- shot. If the stream is a full send stream, this will create the filesystem described by the stream as a clone of the specified snapshot. Which snapshot was specified will not affect the suc- cess or failure of the receive, as long as the snapshot does ex- ist. If the stream is an incremental send stream, all the normal verification will be performed. -F Force a rollback of the file system to the most recent snapshot before performing the receive operation. If receiving an incre- mental replication stream (for example, one generated by "zfs send -R {-i | -I}"), destroy snapshots and file systems that do not exist on the sending side. -s If the receive is interrupted, save the partially received state, rather than deleting it. Interruption may be due to premature termination of the stream (e.g. due to network failure or failure of the remote system if the stream is being read over a network connection), a checksum error in the stream, termination of the zfs receive process, or unclean shutdown of the system. The receive can be resumed with a stream generated by zfs send -t token, where the token is the value of the receive_resume_token property of the filesystem or volume which is received into. To use this flag, the storage pool must have the extensible_dataset feature enabled. See zpool-features(5) for details on ZFS feature flags. Abort an interrupted zfs receive -s, deleting its saved partially re- ceived state. Displays permissions that have been delegated on the specified filesystem or volume. See the other forms of "zfs allow" for more information. Delegates ZFS administration permission for the file systems to non-priv- ileged users. Specifies to whom the permissions are delegated. Multiple entities can be specified as a comma-separated list. If neither of the -ug options are specified, then the argument is interpreted preferentially as the keyword everyone, then as a user name, and lastly as a group name. To specify a user or group named "everyone", use the -u or -g options. To specify a group with the same name as a user, use the -g option. [-e|everyone] Specifies that the permissions be delegated to "everyone". The permissions to delegate. Multiple permissions may be specified as a comma-separated list. Permission names are the same as ZFS subcommand and property names. See the property list below. Property set names, which begin with an at sign (@), may be specified. See the -s form below for details. Specifies where the permissions are delegated. If neither of the -ld op- tions are specified, or both are, then the permissions are allowed for the file system or volume, and all of its descendents. If only the -l op- tion is used, then is allowed "locally" only for the specified file sys- tem. If only the -d option is used, then is allowed only for the descen- dent file systems. Permissions are generally the ability to use a ZFS subcommand or change a ZFS property. The following permissions are available: NAME TYPE NOTES allow subcommand Must also have the permission that is being allowed clone subcommand Must also have the 'create' ability and 'mount' ability in the origin file system create subcommand Must also have the 'mount' ability destroy subcommand Must also have the 'mount' ability diff subcommand Allows lookup of paths within a dataset given an object number, and the ability to create snapshots necessary to 'zfs diff' hold subcommand Allows adding a user hold to a snapshot mount subcommand Allows mount/umount of ZFS datasets promote subcommand Must also have the 'mount' and 'promote' ability in the origin file system receive subcommand Must also have the 'mount' and 'create' ability release subcommand Allows releasing a user hold which might destroy the snapshot rename subcommand Must also have the 'mount' and 'create' ability in the new parent rollback subcommand Must also have the 'mount' ability send subcommand share subcommand Allows sharing file systems over the NFS protocol snapshot subcommand Must also have the 'mount' ability groupquota other Allows accessing any groupquota@... property groupused other Allows reading any groupused@... property userprop other Allows changing any user property userquota other Allows accessing any userquota@... property userused other Allows reading any userused@... property aclinherit property aclmode property atime property canmount property casesensitivity property checksum property compression property copies property dedup property devices property exec property filesystem_limit property logbias property jailed property mlslabel property mountpoint property nbmand property normalization property primarycache property quota property readonly property recordsize property refquota property refreservation property reservation property secondarycache property setuid property sharenfs property sharesmb property snapdir property snapshot_limit property sync property utf8only property version property volblocksize property volsize property vscan property xattr property Sets "create time" permissions. These permissions are granted (locally) to the creator of any newly-created descendent file system. Defines or adds permissions to a permission set. The set can be used by other "zfs allow" commands for the specified file system and its descendents. Sets are evaluated dynamically, so changes to a set are immediately reflected. Per- mission sets follow the same naming restrictions as ZFS file systems, but the name must begin with an "at sign" (@), and can be no more than 64 characters long. Removes permissions that were granted with the "zfs allow" command. No permis- sions are explicitly denied, so other permissions granted are still in effect. For example, if the permission is granted by an ancestor. If no permissions are specified, then all permissions for the specified user, group, or everyone are removed. Specifying everyone (or using the -e option) only removes the permissions that were granted to everyone, not all permissions for every user and group. See the "zfs allow" command for a description of the -ldugec op- tions. -r Recursively remove the permissions from this file system and all de- scendents. Removes permissions from a permission set. If no permissions are specified, then all permissions are removed, thus removing the set entirely. Adds a single reference, named with the tag argument, to the specified snap- shot or snapshots. Each snapshot has its own tag namespace, and tags must be unique within that space. If a hold exists on a snapshot, attempts to destroy that snapshot by using the "zfs destroy" command returns EBUSY. -r Specifies that a hold with the given tag is applied recursively to the snapshots of all descendent file systems. Lists all existing user references for the given dataset or datasets. -H Used for scripting mode. Do not print headers and separate fields by a single tab instead of arbitrary white space. -p Display numbers in parsable (exact) values. -r Lists the holds that are set on the descendent snapshots of the named datasets or snapshots, in addition to listing the holds on the named snapshots, if any. -d depth Recursively display any holds on the named snapshots, or descendent snapshots of the named datasets or snapshots, limiting the recursion to depth. Removes a single reference, named with the tag argument, from the specified snapshot or snapshots. The tag must already exist for each snapshot. -r Recursively releases a hold with the given tag on the snapshots of all descendent file systems. Display the difference between a snapshot of a given filesystem and another snapshot of that filesystem from a later time or the current contents of the filesystem. The first column is a character indicating the type of change, the other columns indicate pathname, new pathname (in case of rename), change in link count, and optionally file type and/or change time. The types of change are: - path was removed + path was added M path was modified R path was renamed -F Display an indication of the type of file, in a manner similar to the -F option of ls(1). B block device C character device F regular file / directory @ symbolic link = socket > door (not supported on FreeBSD) | named pipe (not supported on FreeBSD) P event port (not supported on FreeBSD) -H Give more parsable tab-separated output, without header lines and without arrows. -t Display the path's inode change time as the first column of output. Executes script as a ZFS channel program on pool. The ZFS channel program in- terface allows ZFS administrative operations to be run programmatically via a Lua script. The entire script is executed atomically, with no other adminis- trative operations taking effect concurrently. A library of ZFS calls is made available to channel program scripts. Channel programs may only be run with root privileges. For full documentation of the ZFS channel program interface, see the manual page for zfs-program(8). -j Display channel program output in JSON format. When this flag is specified and standard output is empty - channel program encountered an error. The details of such an error will be printed to standard error in plain text. -n Executes a read-only channel program, which runs faster. The program cannot change on-disk state by calling functions from the zfs.sync submodule. The program can be used to gather information such as properties and determining if changes would succeed (zfs.check.*). Without this flag, all pending changes must be synced to disk before a channel program can complete. -t timeout Execution time limit, in milliseconds. If a channel program executes for longer than the provided timeout, it will be stopped and an error will be returned. The default timeout is 1000 ms, and can be set to a maximum of 10000 ms. -m memory-limit Memory limit, in bytes. If a channel program attempts to allocate more memory than the given limit, it will be stopped and an error re- turned. The default memory limit is 10 MB, and can be set to a maxi- mum of 100 MB. All remaining argument strings are passed directly to the channel pro- gram as arguments. See zfs-program(8) for more information. Attaches the specified filesystem to the jail identified by JID jailid. From now on this file system tree can be managed from within a jail if the jailed property has been set. To use this functionality, the jail needs the allow.mount and allow.mount.zfs parameters set to 1 and the enforce_statfs pa- rameter set to a value lower than 2. See jail(8) for more information on managing jails and configuring the parame- ters above. Detaches the specified filesystem from the jail identified by JID jailid. EXIT STATUS The following exit values are returned: 0 Successful completion. 1 An error occurred. 2 Invalid command line options were specified. EXAMPLES Example 1 Creating a ZFS File System Hierarchy The following commands create a file system named pool/home and a file system named pool/home/bob. The mount point /home is set for the par- ent file system, and is automatically inherited by the child file sys- tem. # zfs create pool/home # zfs set mountpoint=/home pool/home # zfs create pool/home/bob Example 2 Creating a ZFS Snapshot The following command creates a snapshot named yesterday. This snap- shot is mounted on demand in the .zfs/snapshot directory at the root of the pool/home/bob file system. # zfs snapshot pool/home/bob@yesterday Example 3 Creating and Destroying Multiple Snapshots The following command creates snapshots named yesterday of pool/home and all of its descendent file systems. Each snapshot is mounted on de- mand in the .zfs/snapshot directory at the root of its file system. The second command destroys the newly created snapshots. # zfs snapshot -r pool/home@yesterday # zfs destroy -r pool/home@yesterday Example 4 Disabling and Enabling File System Compression The following command disables the compression property for all file systems under pool/home. The next command explicitly enables compression for pool/home/anne. # zfs set compression=off pool/home # zfs set compression=on pool/home/anne Example 5 Listing ZFS Datasets The following command lists all active file systems and volumes in the system. Snapshots are displayed if the listsnaps property is on. The default is off. See zpool(8) for more information on pool properties. # zfs list NAME USED AVAIL REFER MOUNTPOINT pool 450K 457G 18K /pool pool/home 315K 457G 21K /home pool/home/anne 18K 457G 18K /home/anne pool/home/bob 276K 457G 276K /home/bob Example 6 Setting a Quota on a ZFS File System The following command sets a quota of 50 Gbytes for pool/home/bob. # zfs set quota=50G pool/home/bob Example 7 Listing ZFS Properties The following command lists all properties for pool/home/bob. # zfs get all pool/home/bob NAME PROPERTY VALUE SOURCE pool/home/bob type filesystem - pool/home/bob creation Tue Jul 21 15:53 2009 - pool/home/bob used 21K - pool/home/bob available 20.0G - pool/home/bob referenced 21K - pool/home/bob compressratio 1.00x - pool/home/bob mounted yes - pool/home/bob quota 20G local pool/home/bob reservation none default pool/home/bob recordsize 128K default pool/home/bob mountpoint /home/bob default pool/home/bob sharenfs off default pool/home/bob checksum on default pool/home/bob compression on local pool/home/bob atime on default pool/home/bob devices on default pool/home/bob exec on default pool/home/bob filesystem_limit none default pool/home/bob setuid on default pool/home/bob readonly off default pool/home/bob jailed off default pool/home/bob snapdir hidden default pool/home/bob snapshot_limit none default pool/home/bob aclmode discard default pool/home/bob aclinherit restricted default pool/home/bob canmount on default pool/home/bob xattr on default pool/home/bob copies 1 default pool/home/bob version 5 - pool/home/bob utf8only off - pool/home/bob normalization none - pool/home/bob casesensitivity sensitive - pool/home/bob vscan off default pool/home/bob nbmand off default pool/home/bob sharesmb off default pool/home/bob refquota none default pool/home/bob refreservation none default pool/home/bob primarycache all default pool/home/bob secondarycache all default pool/home/bob usedbysnapshots 0 - pool/home/bob usedbydataset 21K - pool/home/bob usedbychildren 0 - pool/home/bob usedbyrefreservation 0 - pool/home/bob logbias latency default pool/home/bob dedup off default pool/home/bob mlslabel - pool/home/bob sync standard default pool/home/bob refcompressratio 1.00x - The following command gets a single property value. # zfs get -H -o value compression pool/home/bob on The following command lists all properties with local settings for pool/home/bob. # zfs get -s local -o name,property,value all pool/home/bob NAME PROPERTY VALUE pool/home/bob quota 20G pool/home/bob compression on Example 8 Rolling Back a ZFS File System The following command reverts the contents of pool/home/anne to the snapshot named yesterday, deleting all intermediate snapshots. # zfs rollback -r pool/home/anne@yesterday Example 9 Creating a ZFS Clone The following command creates a writable file system whose initial con- tents are the same as pool/home/bob@yesterday. # zfs clone pool/home/bob@yesterday pool/clone Example 10 Promoting a ZFS Clone The following commands illustrate how to test out changes to a file system, and then replace the original file system with the changed one, using clones, clone promotion, and renaming: # zfs create pool/project/production Populate /pool/project/production with data and continue with the fol- lowing commands: # zfs snapshot pool/project/production@today # zfs clone pool/project/production@today pool/project/beta Now make changes to /pool/project/beta and continue with the following commands: # zfs promote pool/project/beta # zfs rename pool/project/production pool/project/legacy # zfs rename pool/project/beta pool/project/production Once the legacy version is no longer needed, it can be destroyed. # zfs destroy pool/project/legacy Example 11 Inheriting ZFS Properties The following command causes pool/home/bob and pool/home/anne to in- herit the checksum property from their parent. # zfs inherit checksum pool/home/bob pool/home/anne Example 12 Remotely Replicating ZFS Data The following commands send a full stream and then an incremental stream to a remote machine, restoring them into poolB/received/fs@a and poolB/received/fs@b, respectively. poolB must contain the file system poolB/received, and must not initially contain poolB/received/fs. # zfs send pool/fs@a | ssh host zfs receive poolB/received/fs@a # zfs send -i a pool/fs@b | ssh host zfs receive poolB/received/fs The following command sends a full stream of poolA/fsA/fsB@snap to a remote machine, receiving it into poolB/received/fsA/fsB@snap. The fsA/fsB@snap portion of the received snapshot's name is determined from the name of the sent snapshot. poolB must contain the file system poolB/received. If poolB/received/fsA does not exist, it is created as an empty file system. # zfs send poolA/fsA/fsB@snap | ssh host zfs receive -d poolB/received Example 14 Setting User Properties The following example sets the user-defined com.example:department property for a dataset. # zfs set com.example:department=12345 tank/accounting Example 15 Performing a Rolling Snapshot The following example shows how to maintain a history of snapshots with a consistent naming scheme. To keep a week's worth of snapshots, the user destroys the oldest snapshot, renames the remaining snapshots, and then creates a new snapshot, as follows: # zfs destroy -r pool/users@7daysago # zfs rename -r pool/users@6daysago @7daysago # zfs rename -r pool/users@5daysago @6daysago # zfs rename -r pool/users@4daysago @5daysago # zfs rename -r pool/users@3daysago @4daysago # zfs rename -r pool/users@2daysago @3daysago # zfs rename -r pool/users@yesterday @2daysago # zfs rename -r pool/users@today @yesterday # zfs snapshot -r pool/users@today The following command shows how to set sharenfs property options to en- able root access for a specific network on the tank/home file system. The contents of the sharenfs property are valid exports(5) options. # zfs set sharenfs="maproot=root,network 192.168.0.0/24" tank/home Another way to write this command with the same result is: # set zfs sharenfs="-maproot=root -network 192.168.0.0/24" tank/home The following example shows how to set permissions so that user cindys can create, destroy, mount, and take snapshots on tank/cindys. The permissions on tank/cindys are also displayed. # zfs allow cindys create,destroy,mount,snapshot tank/cindys # zfs allow tank/cindys ---- Permissions on tank/cindys -------------------------------------- Local+Descendent permissions: user cindys create,destroy,mount,snapshot Example 18 Delegating Create Time Permissions on a ZFS Dataset The following example shows how to grant anyone in the group staff to create file systems in tank/users. This syntax also allows staff mem- bers to destroy their own file systems, but not destroy anyone else's file system. The permissions on tank/users are also displayed. # zfs allow staff create,mount tank/users # zfs allow -c destroy tank/users # zfs allow tank/users ---- Permissions on tank/users --------------------------------------- Permission sets: destroy Local+Descendent permissions: group staff create,mount The following example shows how to define and grant a permission set on the tank/users file system. The permissions on tank/users are also dis- played. # zfs allow -s @pset create,destroy,snapshot,mount tank/users # zfs allow staff @pset tank/users # zfs allow tank/users ---- Permissions on tank/users --------------------------------------- Permission sets: @pset create,destroy,mount,snapshot Local+Descendent permissions: group staff @pset Example 20 Delegating Property Permissions on a ZFS Dataset The following example shows to grant the ability to set quotas and reservations on the users/home file system. The permissions on users/home are also displayed. # zfs allow cindys quota,reservation users/home # zfs allow users/home ---- Permissions on users/home --------------------------------------- Local+Descendent permissions: user cindys quota,reservation # su - cindys cindys% zfs set quota=10G users/home/marks cindys% zfs get quota users/home/marks NAME PROPERTY VALUE SOURCE users/home/marks quota 10G local Example 21 Removing ZFS Delegated Permissions on a ZFS Dataset The following example shows how to remove the snapshot permission from the staff group on the tank/users file system. The permissions on tank/users are also displayed. # zfs unallow staff snapshot tank/users # zfs allow tank/users ---- Permissions on tank/users --------------------------------------- Permission sets: @pset create,destroy,mount,snapshot Local+Descendent permissions: group staff @pset Example 22 Showing the differences between a snapshot and a ZFS Dataset The following example shows how to see what has changed between a prior snapshot of a ZFS Dataset and its current state. The -F option is used to indicate type information for the files affected. # zfs diff tank/test@before tank/test M / /tank/test/ M F /tank/test/linked (+1) R F /tank/test/oldname -> /tank/test/newname - F /tank/test/deleted + F /tank/test/created M F /tank/test/modified SEE ALSO chmod(2), fsync(2), exports(5), fstab(5), rc.conf(5), jail(8), mount(8), umount(8), zpool(8) AUTHORS This manual page is a mdoc(7) reimplementation of the OpenSolaris manual page zfs(1M), modified and customized for FreeBSD and licensed under the Common Development and Distribution License (CDDL). The mdoc(7) implementation of this manual page was initially written by Martin Matuska <mm@FreeBSD.org>. FreeBSD 13.0 February 15, 2018 FreeBSD 13.0
NAME | SYNOPSIS | DESCRIPTION | SUBCOMMANDS | EXIT STATUS | EXAMPLES | SEE ALSO | AUTHORS
Want to link to this manual page? Use this URL:
<https://man.freebsd.org/cgi/man.cgi?query=zfs&sektion=8&manpath=FreeBSD+12.1-RELEASE+and+Ports>