misc-utils/blkid.8

   1 .\" Copyright 2000 Andreas Dilger (adilger@turbolinux.com)
   2 .\"
   3 .\" This man page was created for blkid from e2fsprogs-1.25.
   4 .\"
   5 .\" This file may be copied under the terms of the GNU Public License.
   6 .\"
   7 .\" Based on uuidgen, Mon Sep 17 10:42:12 2000, Andreas Dilger
   8 .TH BLKID 8 "February 2009" "Linux" "MAINTENANCE COMMANDS"
   9 .SH NAME
  10 blkid \- command\-line utility to locate/print block device attributes
  11 .SH SYNOPSIS
  12 .B blkid
  13 .RB \-L
  14 .IR label " | "
  15 .RB \-U
  16 .IR uuid
  17
  18 .B blkid
  19 .RB [ \-ghlv ]
  20 .RB [ \-c
  21 .IR file ]
  22 .RB [ \-w
  23 .IR file ]
  24 .RB [ \-o
  25 .IR format ]
  26 .in +6
  27 .RB [ \-s
  28 .IR tag ]
  29 .RB [ \-t
  30 .IR NAME=value ]
  31 [\fIdevice\fR ...]
  32 .in -6
  33
  34 .B blkid
  35 .RB -p
  36 .RB [ \-s
  37 .IR tag ]
  38 .RB [ \-O
  39 .IR offset ]
  40 .RB [ \-S
  41 .IR size ]
  42 .RB [ \-o
  43 .IR format ]
  44 .RB [ \-s
  45 .IR tag ]
  46 .in +9
  47 .RB [ \-n
  48 .IR list ]
  49 .RB [ \-u
  50 .IR list ]
  51 .I device
  52 [\fIdevice\fR ...]
  53
  54 .SH DESCRIPTION
  55 The
  56 .B blkid
  57 program is the command-line interface to working with
  58 .BR libblkid (3)
  59 library.  It can determine the type of content (e.g. filesystem, swap)
  60 a block device holds, and also attributes (tokens, NAME=value pairs)
  61 from the content metadata (e.g. LABEL or UUID fields).
  62 .PP
  63 .B blkid
  64 has two main forms of operation: either searching for a device with a
  65 specific NAME=value pair, or displaying NAME=value pairs for one or
  66 more devices.
  67 .SH OPTIONS
  68 The \fIsize\fR and \fIoffset\fR arguments may be followed by binary (2^N)
  69 suffixes KiB, MiB, GiB, TiB, PiB and EiB (the "iB" is optional, e.g. "K" has the
  70 same meaning as "KiB") or decimal (10^N) suffixes KB, MB, GB, PB and EB.
  71 .TP
  72 .BI \-c " cachefile"
  73 Read from
  74 .I cachefile
  75 instead of reading from the default cache file
  76 .IR /etc/blkid.tab .
  77 If you want to start with a clean cache (i.e. don't report devices previously
  78 scanned but not necessarily available at this time), specify
  79 .IR /dev/null .
  80 .TP
  81 .B \-g
  82 Perform a garbage collection pass on the blkid cache to remove
  83 devices which no longer exist.
  84 .TP
  85 .B \-h
  86 Display a usage message and exit.
  87 .TP
  88 .B \-l
  89 Look up one device that matches the search parameter specified using
  90 the
  91 .B \-t
  92 option.  If there are multiple devices that match the specified search
  93 parameter, then the device with the highest priority is returned, and/or
  94 the first device found at a given priority.  Device types in order of
  95 decreasing priority are Device Mapper, EVMS, LVM, MD, and finally regular
  96 block devices.  If this option is not specified,
  97 .B blkid
  98 will print all of the devices that match the search parameter.
  99 .TP
 100 .B \-L " label "
 101 Look up one device that uses the label (same as: -l -o device -t
 102 LABEL=<label>).  This look up method is able to reliable use /dev/disk/by-label
 103 udev symlinks (depends on setting in /etc/blkid.conf). Avoid to use the
 104 symlinks directly. It is not reliable to use the symlinks without verification.
 105 The \fB-L\fR option works on systems with and without udev.
 106
 107 Unfortunately, the original
 108 .B blkid(8)
 109 from e2fsprogs use the \fB-L\fR option as a
 110 synonym to the \fB-o list\fR option. For better portability use "-l -o device
 111 -t LABEL=<label>" and "-o list" in your scripts rather than -L option.
 112 .TP
 113 .B \-n " list "
 114 Restrict probing functions to defined (comma separated) list of superblock types (names).
 115 The list can be prefixed with "no" to specify the types which should be ignored.
 116 For example:
 117 .sp
 118   blkid -p -n vfat,ext3,ext4 /dev/sda1
 119 .sp
 120 probes for vfat, ext3 and ext4 filesystems, and
 121 .sp
 122   blkid -p -u nominix /dev/sda1
 123 .sp
 124 probes for all supported formats exclude minix filesystem. This option is
 125 useful with
 126 \fB-p\fR only.
 127 .TP
 128 .BI \-o " format"
 129 Display
 130 .BR blkid 's
 131 output using the specified format.  The
 132 .I format
 133 parameter may be:
 134 .RS
 135 .TP
 136 .B full
 137 print all tags (the default)
 138 .TP
 139 .B value
 140 print the value of the tags
 141 .TP
 142 .B list
 143 print the devices in a user-friendly format, this output format is unsupported
 144 for low-level probing (\fB-p\fR)
 145 .TP
 146 .B device
 147 print the device name only, this output format is always enabled for \fB-L\fR
 148 and \fB-U\fR options
 149 .TP
 150 .B udev
 151 vol_id compatible mode; usable in udev rules
 152 .RE
 153 .TP
 154 .BI \-O " offset"
 155 Probe at the given offset (only useful with \fB-p\fR).
 156 .TP
 157 .BI \-p
 158 Switch to low-level probing mode (bypass cache)
 159 .TP
 160 .BI \-s " tag"
 161 For each (specified) device, show only the tags that match
 162 .IR tag .
 163 It is possible to specify multiple
 164 .B \-s
 165 options.  If no tag is specified, then all tokens are shown for all
 166 (specified) devices.
 167 In order to just refresh the cache without showing any tokens, use
 168 .B "-s none"
 169 with no other options.
 170 .TP
 171 .BI \-S " size"
 172 Overwrite device/file size (only useful with \fB-p\fR).
 173 .TP
 174 .BI \-t " NAME" = "value"
 175 Search for block devices with tokens named
 176 .I NAME
 177 that have the value
 178 .IR value ,
 179 and display any devices which are found.
 180 Common values for
 181 .I NAME
 182 include
 183 .BR TYPE ,
 184 .BR LABEL ,
 185 and
 186 .BR UUID .
 187 If there are no devices specified on the command line, all block devices
 188 will be searched; otherwise only the specified devices are searched.
 189 .TP
 190 .B \-u " list "
 191 Restrict probing functions to defined (comma separated) list of "usage" types.
 192 Supported usage types are: filesystem, raid, crypto and other. The list can be
 193 prefixed with "no" to specify the usage types which should be ignored. For example:
 194 .sp
 195   blkid -p -u filesystem,other /dev/sda1
 196 .sp
 197 probes for all filesystems and others (e.g. swap) formats, and
 198 .sp
 199   blkid -p -u noraid /dev/sda1
 200 .sp
 201 probes for all supported formats exclude RAIDs. This option is useful with
 202 \fB-p\fR only.
 203 .TP
 204 .B \-U " uuid "
 205 Look up one device that uses the uuid. For more details see the \fB-L\fR option.
 206 .TP
 207 .B \-v
 208 Display version number and exit.
 209 .TP
 210 .BI \-w " writecachefile"
 211 Write the device cache to
 212 .I writecachefile
 213 instead of writing it to the default cache file
 214 .IR /etc/blkid.tab .
 215 If you don't want to save the cache to the default file, specify
 216 .IR /dev/null.
 217 If not specified it will be the same file as that given by the
 218 .B \-c
 219 option.
 220 .TP
 221 .I device
 222 Display tokens from only the specified device.  It is possible to
 223 give multiple
 224 .I device
 225 options on the command line.  If none is given, all devices which
 226 appear in
 227 .I /proc/partitions
 228 are shown, if they are recognized.
 229 .SH "RETURN CODE"
 230 If the specified token was found, or if any tags were shown from (specified)
 231 devices, 0 is returned.  If the specified token was not found, or no
 232 (specified) devices could be identified, an exit code of 2 is returned.
 233 For usage or other errors, an exit code of 4 is returned.
 234 .SH AUTHOR
 235 .B blkid
 236 was written by Andreas Dilger for libblkid and improved by Theodore Ts'o
 237 and Karel Zak.
 238 .SH AVAILABILITY
 239 The blkid command is part of the util-linux-ng package and is available from
 240 ftp://ftp.kernel.org/pub/linux/utils/util-linux-ng/.
 241 .SH "SEE ALSO"
 242 .BR libblkid (3)
 243 .BR findfs (8)
 244 .BR wipefs (8)