Provided by: util-linux_2.34-0.1ubuntu2_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] [--no-part-details] 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 partitions
       or unpartitioned  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.

       -D, --no-part-details
              Don't print information (PART_ENTRY_*  tags)  from  partition  table  in  low-level
              probing mode.

       -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 value may be modified to
                     be safe for udev environment; allowed is plain ASCII, hex-escaping and valid
                     UTF-8,  everything  else  (including  whitespaces) is replaced with '_'. The
                     keys with _ENC postfix use hex-escaping for unsafe chars.

                     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=). See also --no-part-details.

       -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, or it
       is  impossible to gather any information about the device identifiers or device content 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/.