Provided by: util-linux_2.17.2-0ubuntu1_i386 bug

NAME

       blkid - command-line utility to locate/print block device attributes

SYNOPSIS

       blkid -L label | -U uuid

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

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

DESCRIPTION

       The  blkid  program  is  the  command-line  interface  to  working with
       libblkid(3) library.  It  can  determine  the  type  of  content  (e.g.
       filesystem,  swap)  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 devices.

OPTIONS

       -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
              necessarily available at this time), specify /dev/null.

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

       -h     Display a usage message and exit.

       -l     Look  up  one device that matches the search parameter specified
              using the -t option.  If there are multiple devices  that  match
              the specified search parameter, then the device with the highest
              priority is returned, and/or the first device found at  a  given
              priority.   Device  types  in  order  of decreasing priority are
              Device Mapper, EVMS, LVM, MD, and finally regular block devices.
              If  this  option  is  not specified, blkid will print all of the
              devices that match the search parameter.

       -L  label
              Look up one device that uses the label (same as: -l -o device -t
              LABEL=<label>).   This  look  up  method is able to reliable use
              /dev/disk/by-label  udev  symlinks  (depends   on   setting   in
              /etc/blkid.conf).  Avoid to use 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  to  the  -o  list  option.  For   better
              portability use "-l -o device -t LABEL=<label>" and "-o list" in
              your scripts rather than -L option.

       -u  list
              Restrict probing functions to defined (comma separated) list  of
              "usage"  types.   Supported  usage  types are: filesystem, raid,
              crypto and other. The list can be prefixed with "no" to  specify
              the usage types which should be ignored. For example:

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

              probes for all filesystems and others (e.g. swap) formats, and

                blkid -p -u noraid /dev/sda1

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

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

       -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)

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

              udev   vol_id compatible mode; usable in udev rules

       -O bytes
              Probe at the given offset (only useful with -p).

       -p     Switch to low-level probing mode (bypass cache)

       -s tag For each (specified) device, show only the tags that match  tag.
              It  is  possible  to  specify multiple -s options.  If no tag is
              specified,  then  all  tokens  are  shown  for  all  (specified)
              devices.  In order to just refresh the cache without showing any
              tokens, use -s none with no other options.

       -S bytes
              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.

       -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 to the default file, specify /dev/null.   If  not
              specified  it  will  be  the  same  file as that given by 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
       (specified) 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.

AUTHOR

       blkid  was  written  by  Andreas  Dilger  for  libblkid and improved by
       Theodore Ts’o and Karel Zak.

AVAILABILITY

       The blkid command is part of the util-linux-ng package and is available
       from ftp://ftp.kernel.org/pub/linux/utils/util-linux-ng/.

SEE ALSO

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