blkid


SYNOPSIS
       blkid -L label | -U uuid

       blkid [-dghlv] [-c file] [-w file] [-o format]
             [-s tag] [-t NAME=value] [device ...]

       blkid -p [-O offset] [-S size] [-o format] [-s tag]
                [-n list] [-u list] device ...

       blkid -i [-o format] [-s tag] device ...


DESCRIPTION
       The  blkid  program  is  the command-line interface to working with the
       libblkid(3) library.  It  can  determine  the  type  of  content  (e.g.
       filesystem  or  swap)  that  a  block device holds, and also attributes
       (tokens, NAME=value pairs) from the content  metadata  (e.g.  LABEL  or
       UUID fields).

       blkid  has  two  main forms of operation: either searching for a device
       with a specific NAME=value pair, or displaying NAME=value pairs for one
       or more specified devices.

OPTIONS
       The  size and offset arguments may be followed by binary (2^N) suffixes
       KiB, MiB, GiB, TiB, PiB and EiB (the "iB" is optional, e.g. "K" has the
       same  meaning  as  "KiB") or decimal (10^N) suffixes KB, MB, GB, PB and
       EB.

       -c cachefile
              Read from cachefile instead of reading from  the  default  cache
              file  /etc/blkid.tab.   If  you want to start with a clean cache
              (i.e. don't report devices previously scanned but not  necessar-
              ily available at this time), specify /dev/null.

       -d     Don't  encode  non-printing characters. The non-printing charac-
              ters are encoded by ^ and M- notation by default. Note  that  -o
              udev  output  format  uses a diffrent encoding and this encoding
              cannot be disabled.

       -g     Perform a garbage collection pass on the blkid cache  to  remove
              devices which no longer exist.

       -h     Display a usage message and exit.

       -i     Display I/O Limits (aka I/O topology) information.  The 'export'
              output format is automatically enabled.  This option can be used
              together with the -p option.

       -l     Look up only one device that matches the search parameter speci-
              fied with -t.

       -k     List all known filesystems and RAIDs and exit.
              /dev/disk/by-label udev symlinks  (dependent  on  a  setting  in
              /etc/blkid.conf).   Avoid using the symlinks directly; it is not
              reliable to use  the  symlinks  without  verification.   The  -L
              option works on systems with and without udev.

              Unfortunately,  the  original blkid(8) from e2fsprogs use the -L
              option as a synonym for the -o list option.  For  better  porta-
              bility,  use  -l  -o device -t LABEL=<label> and -o list in your
              scripts rather than the -L option.

       -n list
              Restrict the probing functions  to  the  specified  (comma-sepa-
              rated)  list of superblock types (names).  The list items may be
              prefixed with "no" to specify the types which should be ignored.
              For example:

                blkid -p -n vfat,ext3,ext4 /dev/sda1

              probes for vfat, ext3 and ext4 filesystems, and

                blkid -p -n nominix /dev/sda1

              probes for all supported formats except minix filesystems.  This
              option is only useful together with -p.

       -o format
              Display blkid's output using the specified format.   The  format
              parameter may be:

              full   print all tags (the default)

              value  print the value of the tags

              list   print  the devices in a user-friendly format; this output
                     format is unsupported for low-level probing (-p or -i)

              device print the device name only; this output format is  always
                     enabled for -L and -U options

              udev   print  key="value"  pairs  for  easy import into the udev
                     environment; the keys are prefixed by ID_FS_ or  ID_PART_
                     prefixes

                     The  udev output returns the ID_FS_AMBIVALENT tag if more
                     superblocks are detected, and  ID_PART_ENTRY_*  tags  are
                     always returned for all partitions including empty parti-
                     tions.

              export print key=value pairs for easy import into  the  environ-
                     ment;  this  output  format is automatically enabled when
                     I/O Limits (-i option) are requested

       -O offset
              Probe at the given offset (only useful with  -p).   This  option
              tokens, use -s none with no other options.

       -S size
              Overwrite device/file size (only useful with -p).

       -t NAME=value
              Search  for  block  devices with tokens named NAME that have the
              value value, and display any devices which  are  found.   Common
              values  for NAME include TYPE, LABEL, and UUID.  If there are no
              devices specified on the command line, all block devices will be
              searched; otherwise only the specified devices are searched.

       -u list
              Restrict  the  probing  functions  to the specified (comma-sepa-
              rated) list  of  "usage"  types.   Supported  usage  types  are:
              filesystem,  raid, crypto and other.  The list items may be pre-
              fixed with "no" to specify  the  usage  types  which  should  be
              ignored.  For example:

                blkid -p -u filesystem,other /dev/sda1

              probes for all filesystem and other (e.g. swap) formats, and

                blkid -p -u noraid /dev/sda1

              probes  for  all supported formats except RAIDs.  This option is
              only useful together with -p.

       -U uuid
              Look up the device that uses this uuid.  For  more  details  see
              the -L option.

       -v     Display version number and exit.

       -w writecachefile
              Write  the  device cache to writecachefile instead of writing it
              to the default cache file /etc/blkid.tab.  If you don't want  to
              save  the cache at all, specify /dev/null.  If not specified, it
              will be the same file as that given with the -c option.

       device Display tokens from only the specified device.  It  is  possible
              to give multiple device options on the command line.  If none is
              given, all devices which appear in /proc/partitions  are  shown,
              if they are recognized.

RETURN CODE
       If the specified token was found, or if any tags were shown from (spec-
       ified) devices, 0 is returned.

       If the specified token was not found, or no (specified)  devices  could
       be identified, an exit code of 2 is returned.

       For usage or other errors, an exit code of 4 is returned.

       libblkid(3) findfs(8) wipefs(8)



util-linux                       February 2011                        BLKID(8)
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