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