NAME

       blkid - locate/print block device attributes

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

       -d     Don't  encode non-printing characters. The non-printing characters 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 specified with -t.

       -k     List all known filesystems and RAIDs and exit.

       -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 the device that uses this label (equal to: -l -o device -t LABEL=<label>).
              This lookup method  is  able  to  reliably  use  /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 portability, 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-separated)  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 partitions.

              export print  key=value  pairs  for  easy  import into the environment; 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 can be used  together
              with the -i option.

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

              Note  that  low-level  probing  also returns information about partition table type
              (PTTYPE tag) and partitions (PART_ENTRY_* tags).

       -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 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-separated) list  of  "usage"
              types.   Supported  usage  types are: filesystem, raid, crypto and other.  The list
              items may 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 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 (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.

       If the ambivalent low-level probing result was detected, an exit code of 8 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   package   and   is   available   from
       ftp://ftp.kernel.org/pub/linux/utils/util-linux/.

SEE ALSO

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