Provided by: util-linux_2.31.1-0.4ubuntu3_amd64 bug

NAME

       blkid - locate/print block device attributes

SYNOPSIS

       blkid  --label label | --uuid uuid

       blkid  [--no-encoding  --garbage-collect  --list-one  --cache-file file] [--output format]
              [--match-tag tag] [--match-token NAME=value] [device ...]

       blkid  --probe  [--offset  offset]  [--output  format]  [--size  size]  [--match-tag  tag]
              [--match-types list] [--usages list] device ...

       blkid  --info [--output format] [--match-tag 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, or lsblk
       --fs  to  get  an  overview  of  filesystems,  or  findmnt(8) to search in already mounted
       filesystems.

              lsblk(8) provides more information, better control on output  formatting,  easy  to
              use  in scripts and it does not require root permissions to get actual information.
              blkid reads information directly from devices and for  non-root  users  it  returns
              cached unverified information.  blkid is mostly designed for system services and to
              test libblkid functionality.

       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.

       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.

       For  security  reasons  blkid  silently  ignores  all  devices where the probing result is
       ambivalent (multiple colliding filesystems are detected).  The low-level probing mode (-p)
       provides  more  information  and  extra return code in this case.  It's recommended to use
       wipefs(8) to get a detailed overview and to erase obsolete stuff (magic strings) from  the
       device.

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, --cache-file 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, --no-encoding
              Don't encode non-printing characters.  The non-printing characters are encoded by ^
              and M- notation by default.  Note that the  --output  udev  output  format  uses  a
              different encoding which cannot be disabled.

       -g, --garbage-collect
              Perform  a  garbage  collection  pass on the blkid cache to remove devices which no
              longer exist.

       -h, --help
              Display a usage message and exit.

       -i, --info
              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 --probe
              option.

       -k, --list-filesystems
              List all known filesystems and RAIDs and exit.

       -l, --list-one
              Look up only one device that  matches  the  search  parameter  specified  with  the
              --match-token  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 label
              Look up the device that uses this filesystem label; this  is  equal  to  --list-one
              --output  device --match-token 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 --label 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, --match-types 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 --probe --match-types vfat,ext3,ext4 /dev/sda1

              probes for vfat, ext3 and ext4 filesystems, and

                blkid --probe --match-types nominix /dev/sda1

              probes for all supported formats except minix filesystems.   This  option  is  only
              useful together with --probe.

       -o, --output 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 (--probe or --info).

                     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
                     --label and --uuid 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  (--info  option)  are
                     requested.

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

       -O, --offset offset
              Probe at the given offset (only useful with --probe).   This  option  can  be  used
              together with the --info option.

       -p, --probe
              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  --probe  (for  example  PART_ENTRY_UUID=  vs
              PARTUUID=).

       -s, --match-tag tag
              For  each (specified) device, show only the tags that match tag.  It is possible to
              specify multiple --match-tag 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 --match-tag none with no other options.

       -S, --size size
              Override the size of device/file (only useful with --probe).

       -t, --match-token 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, --usages 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 --probe --usages filesystem,other /dev/sda1

              probes for all filesystem and other (e.g. swap) formats, and

                blkid --probe --usages noraid /dev/sda1

              probes for all supported formats except RAIDs.  This option is only useful together
              with --probe.

       -U, --uuid uuid
              Look  up  the  device  that  uses  this  filesystem uuid.  For more details see the
              --label option.

       -V, --version
              Display version number and exit.

RETURN CODE

       If the specified device or device addressed by specified token (option --match-token)  was
       found  and  it's  possible  to  gather any information about the device, an exit code 0 is
       returned.  Note the option --match-tag 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 probing result was detected by low-level probing mode (-p), 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), lsblk(8), wipefs(8)

AVAILABILITY

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