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blkid


SYNOPSIS

       blkid -L label | -U uuid

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

       blkid -p [-O offset] [-o format] [-S size] [-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 the attributes
       (tokens, NAME=value pairs) from the content  metadata  (e.g.  LABEL  or
       UUID fields).

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

       Note that blkid reads information directly from devices  and  for  non-
       root  users  it returns cached unverified information.  It is better to
       use lsblk --fs to get  a  user-friendly  overview  of  filesystems  and
       devices.   lsblk(8)  is  also  easy to use in scripts.  blkid is mostly
       designed for system services and to test libblkid functionality.

       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  the  multiplicative
       suffixes  like  KiB  (=1024), MiB (=1024*1024), and so on for GiB, TiB,
       PiB, EiB, ZiB and YiB (the "iB" is optional,  e.g.  "K"  has  the  same
       meaning  as "KiB"), or the suffixes KB (=1000), MB (=1000*1000), and so
       on for GB, TB, PB, EB, ZB and YB.

       -c cachefile
              Read from cachefile instead of reading from  the  default  cache
              file  (see the CONFIGURATION FILE section for more details).  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  charac-
              ters are encoded by ^ and M- notation by default.  Note that the
              -o udev output format uses a different encoding which cannot  be
              disabled.
              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 filesystem label; this is
              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 verifi-
              cation.  The -L option works on systems with and without udev.

              Unfortunately, the original blkid(8) from e2fsprogs uses the  -L
              option as a synonym for -o list.  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-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
              Use  the  specified output format.  Note that the order of vari-
              ables and devices is not fixed.  See also option -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).

                     This  output  format  is  DEPRECATED  in  favour  of  the
                     lsblk(8) command.

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

       -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  (bypassing  the
              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
              Override the size of device/file (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  filesystem  uuid.   For  more
              details see the -L option.

       -V     Display version number and exit.


RETURN CODE

       If the specified token was found, or if any tags were shown from (spec-
       ified) devices, 0 is returned.
       SEND_UEVENT=<yes|not>
              Sends uevent when  /dev/disk/by-{label,uuid,partuuid,partlabel}/
              symlink  does  not match with LABEL, UUID, PARTUUID or PARTLABEL
              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 a /run directory.

       EVALUATE=<methods>
              Defines  LABEL  and  UUID  evaluation method(s).  Currently, the
              libblkid library supports the "udev" and "scan"  methods.   More
              than  one  method  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.


ENVIRONMENT

       Setting LIBBLKID_DEBUG=0xffff enables debug output.


SEE ALSO

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


AVAILABILITY

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


util-linux March 2013 BLKID(8)



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