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GEOM_UZIP(4) Kernel Interfaces Manual GEOM_UZIP(4) NAME geom_uzip -- GEOM based compressed disk images and partitions SYNOPSIS To compile this driver into the kernel, place the following line in your kernel configuration file: device xz options zstd options GEOM_UZIP Alternatively, to load the driver as a module at boot time, place the following line in loader.conf(5): geom_uzip_load="YES" DESCRIPTION The geom_uzip framework provides support for compressed read-only disk images. This allows significant storage savings at the expense of some CPU time on each read. Data written in the GEOM label area allows geom_uzip to detect compressed images which have been created with mkuzip(8) and presented to the kernel as a logical disk device via md(4). geom_uzip creates a unique md#.uzip device for each image. geom_uzip is not limited to supporting only md(4) images. The image can also reside on a block device. (For example, a disk, USB flash drive, DVD-ROM, etc). The appropriate device node will appear with the .uzip suffix. # gpart show da0 => 0 7833600 da0 BSD (3.7G) 0 2097152 1 freebsd-ufs (1.0G) 2097152 5736448 - free - (2.7G) # gpart add -t freebsd-ufs -s 1G da0 da0b added # dd if=/tmp/20160217_dcomp_zcomp.uzip bs=256k of=/dev/da0b 3190+1 records in 3190+1 records out 836331008 bytes transferred in 111.021489 secs (7533055 bytes/sec) # fsck -t ffs /dev/da0b.uzip ** /dev/da0b.uzip (NO WRITE) ** Last Mounted on /mnt ** Phase 1 - Check Blocks and Sizes ** Phase 2 - Check Pathnames ** Phase 3 - Check Connectivity ** Phase 4 - Check Reference Counts ** Phase 5 - Check Cyl groups 97455 files, 604242 used, 184741 free (2349 frags, 22799 blocks, 0.3% fragmentation) # mount -o ro /dev/da0b.uzip /mnt # df /dev/da0b.uzip Filesystem 1K-blocks Used Avail Capacity Mounted on /dev/da0b.uzip 3155932 2416968 738964 77% /mnt The geom_uzip device is subsequently used by FreeBSD kernel to access the uncompressed data. The geom_uzip driver does not allow write oper- ations to the underlying disk image. To check which "providers" match a given geom_uzip device: # geom uzip list Geom name: md1.uzip Providers: 1. Name: md1.uzip Mediasize: 22003712 (21M) Sectorsize: 512 Consumers: 1. Name: md1 Mediasize: 9563648 (9.1M) Sectorsize: 512 Geom name: da0b.uzip Providers: 1. Name: da0b.uzip Mediasize: 3355443200 (3.1G) Sectorsize: 512 Consumers: 1. Name: da0b Mediasize: 1073741824 (1.0G) Sectorsize: 512 geom_uzip allows mounting the root file system from a compressed disk partition by setting the vfs.root.mountfrom tunable. See loader.conf(5) for details. DIAGNOSTICS Several flags are provided for tracing geom_uzip I/O operations and TOC parsing via the following sysctls. kern.geom.uzip.debug Log level. Zero disables logging. Higher values enable more verbose debug logging for geom_uzip. Supported levels are from 0 (no logging) to 4 (maximum amount of logging). kern.geom.uzip.debug_block Log operations involving compressed cluster number. SEE ALSO GEOM(4), md(4), geom(8), mkuzip(8) HISTORY Zstd support was added in FreeBSD 13.0. AUTHORS The geom_uzip driver was written by Max Khon <fjoe@FreeBSD.org>. The block de-duplication code as well as some geom_uzip driver optimiza- tions have been contributed by Maxim Sobolev <sobomax@FreeBSD.org>. The LZMA decompression support and CLOOP 3.0 support have been added by Aleksandr Rybalko <ray@FreeBSD.org>. This manual page was written by Ceri Davies <ceri@FreeBSD.org>. FreeBSD 14.3 April 28, 2021 GEOM_UZIP(4)
NAME | SYNOPSIS | DESCRIPTION | DIAGNOSTICS | SEE ALSO | HISTORY | AUTHORS
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