262 lines
7.1 KiB
Groff
262 lines
7.1 KiB
Groff
.\" Copyright 2000 Andreas Dilger (adilger@turbolinux.com)
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.\"
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.\" This man page was created for blkid from e2fsprogs-1.25.
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.\"
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.\" This file may be copied under the terms of the GNU Public License.
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.\"
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.\" Based on uuidgen, Mon Sep 17 10:42:12 2000, Andreas Dilger
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.TH BLKID 8 "February 2009" "Linux" "MAINTENANCE COMMANDS"
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.SH NAME
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blkid \- command\-line utility to locate/print block device attributes
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.SH SYNOPSIS
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.B blkid
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.RB \-L
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.IR label " | "
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.RB \-U
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.IR uuid
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.B blkid
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.RB [ \-ghlv ]
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.RB [ \-c
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.IR file ]
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.RB [ \-w
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.IR file ]
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.RB [ \-o
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.IR format ]
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.in +6
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.RB [ \-s
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.IR tag ]
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.RB [ \-t
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.IR NAME=value ]
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[\fIdevice\fR ...]
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.in -6
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.B blkid
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.RB -p
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.RB [ \-O
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.IR offset ]
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.RB [ \-S
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.IR size ]
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.RB [ \-o
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.IR format ]
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.RB [ \-s
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.IR tag ]
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.in +9
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.RB [ \-n
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.IR list ]
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.RB [ \-u
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.IR list ]
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.I device
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[\fIdevice\fR ...]
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.in -9
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.B blkid
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.RB -i
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.RB [ \-o
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.IR format ]
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.RB [ \-s
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.IR tag ]
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.I device
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[\fIdevice\fR ...]
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.SH DESCRIPTION
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The
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.B blkid
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program is the command-line interface to working with
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.BR libblkid (3)
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library. It can determine the type of content (e.g. filesystem, swap)
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a block device holds, and also attributes (tokens, NAME=value pairs)
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from the content metadata (e.g. LABEL or UUID fields).
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.PP
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.B blkid
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has two main forms of operation: either searching for a device with a
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specific NAME=value pair, or displaying NAME=value pairs for one or
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more devices.
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.SH OPTIONS
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The \fIsize\fR and \fIoffset\fR arguments may be followed by binary (2^N)
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suffixes KiB, MiB, GiB, TiB, PiB and EiB (the "iB" is optional, e.g. "K" has the
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same meaning as "KiB") or decimal (10^N) suffixes KB, MB, GB, PB and EB.
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.TP
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.BI \-c " cachefile"
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Read from
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.I cachefile
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instead of reading from the default cache file
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.IR /etc/blkid.tab .
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If you want to start with a clean cache (i.e. don't report devices previously
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scanned but not necessarily available at this time), specify
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.IR /dev/null .
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.TP
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.B \-g
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Perform a garbage collection pass on the blkid cache to remove
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devices which no longer exist.
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.TP
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.B \-h
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Display a usage message and exit.
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.TP
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.B \-i
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Display I/O Limits (aka I/O topology) information. The 'export' output format is
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automatically enabled. This option could be used together with \fB-p\fR option.
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.TP
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.B \-l
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Look up one device that matches the search parameter specified using
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the
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.B \-t
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option. If there are multiple devices that match the specified search
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parameter, then the device with the highest priority is returned, and/or
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the first device found at a given priority. Device types in order of
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decreasing priority are Device Mapper, EVMS, LVM, MD, and finally regular
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block devices. If this option is not specified,
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.B blkid
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will print all of the devices that match the search parameter.
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.TP
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.B \-L " label "
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Look up one device that uses the label (same as: -l -o device -t
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LABEL=<label>). This look up method is able to reliable use /dev/disk/by-label
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udev symlinks (depends on setting in /etc/blkid.conf). Avoid to use the
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symlinks directly. It is not reliable to use the symlinks without verification.
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The \fB-L\fR option works on systems with and without udev.
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Unfortunately, the original
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.B blkid(8)
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from e2fsprogs use the \fB-L\fR option as a
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synonym to the \fB-o list\fR option. For better portability use "-l -o device
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-t LABEL=<label>" and "-o list" in your scripts rather than -L option.
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.TP
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.B \-n " list "
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Restrict probing functions to defined (comma separated) list of superblock types (names).
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The list can be prefixed with "no" to specify the types which should be ignored.
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For example:
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.sp
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blkid -p -n vfat,ext3,ext4 /dev/sda1
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.sp
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probes for vfat, ext3 and ext4 filesystems, and
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.sp
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blkid -p -u nominix /dev/sda1
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.sp
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probes for all supported formats exclude minix filesystem. This option is
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useful with
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\fB-p\fR only.
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.TP
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.BI \-o " format"
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Display
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.BR blkid 's
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output using the specified format. The
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.I format
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parameter may be:
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.RS
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.TP
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.B full
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print all tags (the default)
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.TP
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.B value
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print the value of the tags
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.TP
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.B list
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print the devices in a user-friendly format, this output format is unsupported
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for low-level probing (\fB-p\fR or \fB-i\fR)
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.TP
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.B device
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print the device name only, this output format is always enabled for \fB-L\fR
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and \fB-U\fR options
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.TP
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.B udev
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print key="value" pairs for easy import into the udev environment
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.TP
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.B export
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print key=value pairs for easy import into the environment. This output format
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is automatically enabled when I/O Limits (\fB-i\fR option) are requested.
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.RE
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.TP
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.BI \-O " offset"
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Probe at the given offset (only useful with \fB-p\fR). This option could be
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used together with \fB-i\fR option.
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.TP
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.BI \-p
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Switch to low-level superblock probing mode (bypass cache).
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.TP
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.BI \-s " tag"
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For each (specified) device, show only the tags that match
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.IR tag .
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It is possible to specify multiple
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.B \-s
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options. If no tag is specified, then all tokens are shown for all
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(specified) devices.
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In order to just refresh the cache without showing any tokens, use
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.B "-s none"
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with no other options.
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.TP
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.BI \-S " size"
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Overwrite device/file size (only useful with \fB-p\fR).
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.TP
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.BI \-t " NAME" = "value"
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Search for block devices with tokens named
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.I NAME
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that have the value
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.IR value ,
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and display any devices which are found.
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Common values for
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.I NAME
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include
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.BR TYPE ,
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.BR LABEL ,
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and
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.BR UUID .
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If there are no devices specified on the command line, all block devices
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will be searched; otherwise only the specified devices are searched.
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.TP
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.B \-u " list "
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Restrict probing functions to defined (comma separated) list of "usage" types.
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Supported usage types are: filesystem, raid, crypto and other. The list can be
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prefixed with "no" to specify the usage types which should be ignored. For example:
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.sp
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blkid -p -u filesystem,other /dev/sda1
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.sp
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probes for all filesystems and others (e.g. swap) formats, and
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.sp
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blkid -p -u noraid /dev/sda1
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.sp
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probes for all supported formats exclude RAIDs. This option is useful with
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\fB-p\fR only.
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.TP
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.B \-U " uuid "
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Look up one device that uses the uuid. For more details see the \fB-L\fR option.
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.TP
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.B \-v
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Display version number and exit.
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.TP
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.BI \-w " writecachefile"
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Write the device cache to
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.I writecachefile
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instead of writing it to the default cache file
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.IR /etc/blkid.tab .
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If you don't want to save the cache to the default file, specify
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.IR /dev/null.
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If not specified it will be the same file as that given by the
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.B \-c
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option.
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.TP
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.I device
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Display tokens from only the specified device. It is possible to
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give multiple
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.I device
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options on the command line. If none is given, all devices which
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appear in
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.I /proc/partitions
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are shown, if they are recognized.
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.SH "RETURN CODE"
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If the specified token was found, or if any tags were shown from (specified)
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devices, 0 is returned. If the specified token was not found, or no
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(specified) devices could be identified, an exit code of 2 is returned.
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For usage or other errors, an exit code of 4 is returned.
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.SH AUTHOR
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.B blkid
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was written by Andreas Dilger for libblkid and improved by Theodore Ts'o
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and Karel Zak.
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.SH AVAILABILITY
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The blkid command is part of the util-linux package and is available from
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ftp://ftp.kernel.org/pub/linux/utils/util-linux/.
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.SH "SEE ALSO"
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.BR libblkid (3)
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.BR findfs (8)
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.BR wipefs (8)
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