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Linux 2.6 - man page for blkid (linux section 8)


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

       blkid -L label | -U uuid

       blkid [-ghlv] [-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 [device ...]

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

       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

       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.

       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.

       -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 could be used together with -p option.

       -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 sys-
	      tems 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.

       -n  list
	      Restrict probing functions to defined (comma separated) list  of	superblock  types
	      (names).	 The  list can 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 -u nominix /dev/sda1

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

       -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 unsup-
		     ported 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	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 could be used together
	      with -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 dis-
	      play  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	probing  functions  to	defined  (comma separated) list of "usage" types.
	      Supported usage types are: filesystem, raid, crypto and other. The list can 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 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.

       -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.

       If the specified token was found, or if any tags were shown from (specified) devices, 0 is

       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.

       blkid was written by Andreas Dilger for libblkid and improved by Theodore Ts'o  and  Karel

       The  blkid  command is part of the util-linux package and is available from ftp://ftp.ker-

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

Linux					  February 2009 				 BLKID(8)

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