blkid man page on Pidora

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BLKID(8)		     System Administration		      BLKID(8)

NAME
       blkid - locate/print block device attributes

SYNOPSIS
       blkid -L label | -U uuid

       blkid [-dghlv] [-c 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  (see CONFIGURATION FILE section for more details).	If you
	      want to start with a clean cache (i.e. don't report devices pre‐
	      viously  scanned	but  not  necessarily 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.

       -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 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. Note that the
	      variables order and devices order is variable. See also -s.  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
	      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 par‐
	      tition 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-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.

       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.

       If the ambivalent low-level probing result was detected, an  exit  code
       of 8 is returned.

CONFIGURATION FILE
       The  standard  location of the /etc/blkid.conf config file can be over‐
       ridden by the environment variable BLKID_CONF.  The  following  options
       control the libblkid library:

       SEND_UEVENT=<yes|not>
	      Sends  uevent  when  /dev/disk/by-{label,uuid}/ symlink does not
	      match with LABEL or UUID on the device. Default is "yes".

       CACHE_FILE=<path>
	      Overrides the standard location of the cache file. This  setting
	      can  be  overridden  by  the  environment	 variable  BLKID_FILE.
	      Default is /run/blkid/blkid.tab  or  /etc/blkid.tab  on  systems
	      without /run direcotry

       EVALUATE=<methods>
	      Defines LABEL and UUID evaluation method(s). Currently, the lib‐
	      blkid library supports "udev" and "scan" methods. More than  one
	      methods  may  be specified in a comma separated list. Default is
	      "udev,scan". The "udev" method uses udev /dev/disk/by-* symlinks
	      and   the	 "scan"	 method	 scans	all  block  devices  from  the
	      /proc/partitions file.

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)

util-linux			 February 2011			      BLKID(8)
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