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, --hint setting
	   Set probing hint. The hints are an optional way 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.

	   json
	       Print the tags entries in JSON objects.

       -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.

       -h, --help
	   Display help text and exit.

       -V, --version
	   Display version 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
       <https://github.com/util-linux/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 2.41.2		  2025-09-22			      BLKID(8)