Man page of BLKID
Section: MAINTENANCE COMMANDS (8)
Updated: February 2009
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blkid - command-line utility to locate/print block device attributes
program is the command-line interface to working with
library. It can determine the type of content (e.g. filesystem, swap)
a block device holds, and also attributes (tokens, NAME=value pairs)
from the content metadata (e.g. LABEL or UUID fields).
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
- -c cachefile
instead of reading from the default cache file
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
Perform a garbage collection pass on the blkid cache to remove
devices which no longer exist.
Display a usage message and exit.
Look up one device that matches the search parameter specified using
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,
will print all of the devices that match the search parameter.
- -L label
Look up one device that uses the label (same as: -l -o device -t
LABEL=<label>). This look up method is able to reliable use /dev/disk/by-label
udev symlinks (depends on setting in /etc/blkid.conf). Avoid to use the
symlinks directly. It is not reliable to use the symlinks without verification.
The -L option is portable and works on systems with and without udev.
- -u list
Restrict probing functions to defined (comma separated) list of "usage" types.
Supported usage types are: filesystem, raid, crypto and other. The list can be
prefixed with "no" to specify the usage types which should be ignored. For example:
blkid -p -u filesystem,other /dev/sda1
probes for all filesystems and others (e.g. swap) formats, and
blkid -p -u noraid /dev/sda1
probes for all supported formats exclude RAIDs. This option is useful with
- -U uuid
Look up one device that uses the uuid. For more details see the -L option.
- -o format
output using the specified format. The
parameter may be:
print all tags (the default)
print the value of the tags
print the devices in a user-friendly format
print the device name only
vol_id compatible mode; usable in udev rules
- -O bytes
Probe at the given offset (only useful with -p).
Switch to low-level probing mode (bypass cache)"
- -s tag
For each (specified) device, show only the tags that match
It is possible to specify multiple
options. If no tag is specified, then all tokens are shown for all
In order to just refresh the cache without showing any tokens, use
with no other options.
- -S bytes
Overwrite device/file size (only useful with -p).
- -t NAME=value
Search for block devices with tokens named
that have the value
and display any devices which are found.
Common values for
If there are no devices specified on the command line, all block devices
will be searched; otherwise only the specified devices are searched.
Display version number and exit.
- -w writecachefile
Write the device cache to
instead of writing it to the default cache file
If you don't want to save the cache to the default file, specify
If not specified it will be the same file as that given by the
Display tokens from only the specified device. It is possible to
options on the command line. If none is given, all devices which
are shown, if they are recognized.
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.
was written by Andreas Dilger for libblkid and improved by Theodore Ts'o
and Karel Zak.
The blkid command is part of the util-linux-ng package and is available from
- RETURN CODE
- SEE ALSO
This document was created by
using the manual pages.
Time: 04:17:50 GMT, September 24, 2010