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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)

Want to link to this manual page? Use this URL:
<https://man.freebsd.org/cgi/man.cgi?query=geom_uzip&sektion=4&manpath=FreeBSD+14.3-RELEASE+and+Ports>

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