181 lines
5.0 KiB
Groff
181 lines
5.0 KiB
Groff
.\"
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.\" Copyright (c) 2006 Ceri Davies
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd February 26, 2019
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.Dt GEOM_UZIP 4
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.Os
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.Sh NAME
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.Nm geom_uzip
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.Nd "GEOM based compressed disk images and partitions"
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.Sh SYNOPSIS
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To compile this driver into the kernel,
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place the following line in your
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kernel configuration file:
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.Bd -ragged -offset indent
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.Cd "device xz"
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.Cd "options GEOM_UZIP"
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.Ed
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.Pp
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Alternatively, to load the driver as a
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module at boot time, place the following line in
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.Xr loader.conf 5 :
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.Bd -literal -offset indent
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geom_uzip_load="YES"
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.Ed
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.Sh DESCRIPTION
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The
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.Nm
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framework provides support for compressed read-only
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disk images.
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This allows significant storage savings at the expense of
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a some CPU time on each read.
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Data written in the GEOM label area allows
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.Nm
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to detect compressed images which have been created with
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.Xr mkuzip 8
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and presented to the kernel as a logical disk device via
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.Xr md 4 .
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.Nm
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creates a unique
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.Pa md#.uzip
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device for each image.
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.Pp
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.Nm
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is not limited to supporting only
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.Xr md 4
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images.
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The image can also reside on a block device.
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.Pq For example, a disk, USB flash drive, DVD-ROM, etc.
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The appropriate device node will appear with the
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.Pa .uzip
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suffix.
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.Bd -literal -offset indent
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# gpart show da0
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=> 0 7833600 da0 BSD (3.7G)
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0 2097152 1 freebsd-ufs (1.0G)
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2097152 5736448 - free - (2.7G)
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# gpart add -t freebsd-ufs -s 1G da0
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da0b added
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# dd if=/tmp/20160217_dcomp_zcomp.uzip bs=256k of=/dev/da0b
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3190+1 records in
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3190+1 records out
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836331008 bytes transferred in 111.021489 secs (7533055 bytes/sec)
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# fsck -t ffs /dev/da0b.uzip
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** /dev/da0b.uzip (NO WRITE)
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** Last Mounted on /mnt
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** Phase 1 - Check Blocks and Sizes
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** Phase 2 - Check Pathnames
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** Phase 3 - Check Connectivity
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** Phase 4 - Check Reference Counts
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** Phase 5 - Check Cyl groups
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97455 files, 604242 used, 184741 free (2349 frags, 22799 blocks,
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0.3% fragmentation)
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# mount -o ro /dev/da0b.uzip /mnt
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# df /dev/da0b.uzip
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Filesystem 1K-blocks Used Avail Capacity Mounted on
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/dev/da0b.uzip 3155932 2416968 738964 77% /mnt
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.Ed
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.Pp
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The
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.Nm
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device is subsequently used by
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.Fx
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kernel to access the uncompressed data.
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The
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.Nm
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driver does not allow write operations to the underlying disk image.
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To check which
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.Dq providers
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match a given
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.Nm
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device:
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.Bd -literal -offset indent
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# geom uzip list
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Geom name: md1.uzip
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Providers:
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1. Name: md1.uzip
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Mediasize: 22003712 (21M)
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Sectorsize: 512
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Consumers:
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1. Name: md1
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Mediasize: 9563648 (9.1M)
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Sectorsize: 512
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Geom name: da0b.uzip
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Providers:
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1. Name: da0b.uzip
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Mediasize: 3355443200 (3.1G)
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Sectorsize: 512
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Consumers:
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1. Name: da0b
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Mediasize: 1073741824 (1.0G)
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Sectorsize: 512
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.Ed
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.Pp
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.Nm
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allows mounting the root file system from a compressed disk partition by
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setting the
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.Dv vfs.root.mountfrom
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tunable.
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See
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.Xr loader.conf 5
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for details.
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.Sh DIAGNOSTICS
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Several flags are provided for tracing
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.Nm
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I/O operations and TOC parsing via the following sysctls.
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.Bl -tag -width indent
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.It Va kern.geom.uzip.debug
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Log level.
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Zero disables logging.
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Higher values enable more verbose debug logging for
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.Nm .
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Supported levels are from 0 (no logging) to 4 (maximum amount of logging).
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.It Va kern.geom.uzip.debug_block
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Log operations involving compressed cluster number.
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.El
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.Sh SEE ALSO
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.Xr GEOM 4 ,
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.Xr md 4 ,
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.Xr geom 8 ,
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.Xr mkuzip 8
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.Sh AUTHORS
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.An -nosplit
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The
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.Nm
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driver was written by
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.An Max Khon Aq Mt fjoe@FreeBSD.org .
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The block de-duplication code as well as some
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.Nm
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driver optimizations have been contributed by
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.An Maxim Sobolev Aq Mt sobomax@FreeBSD.org .
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The LZMA decompression support and CLOOP 3.0 support have been added by
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.An Aleksandr Rybalko Aq Mt ray@FreeBSD.org .
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.Pp
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This manual page was written by
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.An Ceri Davies Aq Mt ceri@FreeBSD.org .
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