Copyright (c) 2006 Ceri Davies
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$FreeBSD: releng/11.0/share/man/man4/geom_uzip.4 295943 2016-02-23 23:59:08Z sobomax $
.Dd October 9, 2006 .Dt GEOM_UZIP 4 .Os .Sh NAME .Nm geom_uzip .Nd "GEOM based compressed disk images and partitions" .Sh SYNOPSIS To compile this driver into the kernel, place the following line in your kernel configuration file: d -ragged -offset indent .Cd "options GEOM_UZIP" .Ed
p Alternatively, to load the driver as a module at boot time, place the following line in .Xr loader.conf 5 : d -literal -offset indent geom_uzip_load="YES" .Ed .Sh DESCRIPTION The .Nm framework provides support for compressed read-only disk images. This allows significant storage savings at the expense of a some CPU time on each read. Data written in the GEOM label area allows .Nm to detect compressed images which have been created with .Xr mkuzip 8 and presented to the kernel as a logical disk device via .Xr md 4 . .Nm creates a unique
a md#.uzip device for each image.
p .Nm is not limited to supporting only .Xr md 4 images. The image can also reside on a block device.
q For example, a disk, USB flash drive, DVD-ROM, etc. The appropriate device node will appear with the
a .uzip suffix. d -literal -offset indent # 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 .Ed
p The .Nm device is subsequently used by .Fx kernel to access the uncompressed data. The .Nm driver does not allow write operations to the underlying disk image. To check which .Dq providers match a given .Nm device: d -literal -offset indent # 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 .Ed
p .Nm allows mounting the root file system from a compressed disk partition by setting the .Dv vfs.root.mountfrom tunable. See .Xr loader.conf 5 for details. .Sh DIAGNOSTICS Several flags are provided for tracing .Nm I/O operations and TOC parsing via the following sysctls. l -tag -width indent t Va kern.geom.uzip.debug Log level. Zero disables logging. Higher values enable more verbose debug logging for .Nm . Supported levels are from 0 (no logging) to 4 (maximum amount of logging). t Va kern.geom.uzip.debug_block Log operations involving compressed cluster number. .El .Sh SEE ALSO .Xr GEOM 4 , .Xr md 4 , .Xr geom 8 , .Xr mkuzip 8 .Sh AUTHORS .An -nosplit The .Nm driver was written by .An Max Khon Aq Mt fjoe@FreeBSD.org . The block de-duplication code as well as some .Nm driver optimizations have been contributed by .An Maxim Sobolev Aq Mt sobomax@FreeBSD.org . The LZMA decompression support and CLOOP 3.0 support have been added by .An Aleksandr Rybalko Aq Mt ray@FreeBSD.org .
p This manual page was written by .An Ceri Davies Aq Mt ceri@FreeBSD.org .