blkid (8)
NAME
blkid - locate/print block device attributesSYNOPSIS
blkid -L label | -U uuidblkid [-dghlv] [-c file] [-w file] [-o format] [-s tag] [-t NAME=value] [device ...]
blkid -p [-O offset] [-S size] [-o format] [-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 attributes (tokens, NAME=value pairs) from the content metadata (e.g. LABEL or UUID fields).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 binary (2^N) suffixes KiB, MiB, GiB, TiB, PiB and EiB (the "iB" is optional, e.g. "K" has the same meaning as "KiB") or decimal (10^N) suffixes KB, MB, GB, PB and EB.- -c cachefile
- Read from cachefile instead of reading from the default cache file /etc/blkid.tab. 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 -o udev output format uses a diffrent encoding and this encoding 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 I/O Limits (aka I/O topology) information. The 'export' output format is automatically enabled. This option can be used together with the -p option.
- -l
- Look up only one device that matches the search parameter specified with -t.
- -k
- List all known filesystems and RAIDs and exit.
- -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 label (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 use the -L option as a synonym for the -o list option. 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/sda1probes for vfat, ext3 and ext4 filesystems, and
blkid -p -n nominix /dev/sda1probes for all supported formats except minix filesystems. This option is only useful together with -p.
- -o format
-
Display
blkid's
output using the specified format. 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)
- device
- print the device name only; this output format is always enabled for -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.
- 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
-
- -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 (bypass cache).
Note that low-level probing also returns information about partition table type (PTTYPE tag) and partitions (PART_ENTRY_* tags).
- -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
- Overwrite device/file size (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/sda1probes for all filesystem and other (e.g. swap) formats, and
blkid -p -u noraid /dev/sda1probes for all supported formats except RAIDs. This option is only useful together with -p.
- -U uuid
- Look up the device that uses this uuid. For more details see the -L option.
- -v
- Display version number and exit.
- -w writecachefile
- Write the device cache to writecachefile instead of writing it to the default cache file /etc/blkid.tab. If you don't want to save the cache at all, specify /dev/null. If not specified, it will be the same file as that given with the -c option.
- device
- Display tokens from only the specified device. It is possible to give multiple device options on the command line. If none is given, all devices which appear in /proc/partitions are shown, if they are recognized.
RETURN CODE
If the specified token was found, or if any tags were shown from (specified) devices, 0 is returned.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 the ambivalent low-level probing result was detected, an exit code of 8 is returned.
AUTHOR
blkid was written by Andreas Dilger for libblkid and improved by Theodore Ts'o and Karel Zak.AVAILABILITY
The blkid command is part of the util-linux package and is available from ftp://ftp.kernel.org/pub/linux/utils/util-linux/.SEE ALSO
libblkid(3) findfs(8) wipefs(8)