blkid

BLKID(8)                     System Administration                    BLKID(8)

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(3)
          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 exit status 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.

       -H, --hint setting
           Set probing hint. The hints are optional way how to force probing
           functions to check for example another location. The currently
           supported is "session_offset=number" to set session offset on
           multi-session UDF.

       -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 (but see below note about udev). 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.

           This option forces blkid to use udev when used for LABEL or UUID
           tokens in --match-token. The goal is to provide output consistent
           with other utils (like mount(8), etc.) on systems where the same
           tag is used for multiple devices.

       -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.

EXIT STATUS
       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 status 0 is returned. Note the option
       --match-tag filters output tags, but it does not affect exit status.

       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 status of 2 is returned.

       For usage or other errors, an exit status of 4 is returned.

       If an ambivalent probing result was detected by low-level probing mode
       (-p), an exit status 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.

ENVIRONMENT
       Setting LIBBLKID_DEBUG=all enables debug output.

AUTHORS
       blkid was written by Andreas Dilger for libblkid and improved by
       Theodore Ts'o and Karel Zak.

SEE ALSO
       libblkid(3), findfs(8), lsblk(8), wipefs(8)

REPORTING BUGS
       For bug reports, use the issue tracker at
       https://github.com/karelzak/util-linux/issues.

AVAILABILITY
       The blkid command is part of the util-linux package which can be
       downloaded from Linux Kernel Archive
       <https://www.kernel.org/pub/linux/utils/util-linux/>.

util-linux 2.37.2                 2021-07-20                          BLKID(8)