Provided by: util-linux_2.27.1-6ubuntu2_i386 bug

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] [-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).

       It  is  recommended  to  use  lsblk(8) command to get information about
       block devices rather than blkid.  lsblk(8) provides  more  information,
       better  control  on  output  formatting  and  it  does not require root
       permissions to get actual information.

       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
              characters are encoded by ^ and M- notation  by  default.   Note
              that  the  -o udev output format uses a different encoding which
              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  information  about  I/O Limits (aka I/O topology).  The
              'export' output format is automatically  enabled.   This  option
              can be used together with the -p option.

       -k     List all known filesystems and RAIDs and exit.

       -l     Look  up  only  one  device  that  matches  the search parameter
              specified with 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 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
              verification.   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-
              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
              Use  the  specified  output  format.   Note  that  the  order of
              variables 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

              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.  This output format is DEPRECATED.

              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.

                     The  non-printing  characters  are  encoded  by  ^ and M-
                     notation  and  all  potentially  unsafe  characters   are
                     escaped.

       -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
              partition table type (PTTYPE tag) and  partitions  (PART_ENTRY_*
              tags).  The tag names produced by low-level probing are based on
              names used internally by libblkid and it may be  different  than
              when  executed  without  -p  (for  example  PART_ENTRY_UUID=  vs
              PARTUUID=).

       -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-
              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 filesystem uuid.  For more
              details see the -L option.

       -V     Display version number and exit.

RETURN CODE

       If the specified device or device addressed by specified token  (option
       -t)  was  found  and  it's possible to gather any information about the
       device, an exit code 0 is returned.  Note the option -s filters  output
       tags, but it does not affect return code.

       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 an 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
       overridden 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,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=all enables debug output.

SEE ALSO

       libblkid(3), findfs(8), wipefs(8), lsblk(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/.