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
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.
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 works on systems with and without udev.
Unfortunately, the original
from e2fsprogs use the -L option as a
synonym to the -o list option. For better portability use "-l -o device
-t LABEL=<label>" and "-o list" in your scripts rather than -L option.
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
Look up one device that uses the uuid. For more details see the -L option.
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, this output format is unsupported
for low-level probing (-p)
print the device name only, this output format is always enabled for -L
and -U options
vol_id compatible mode; usable in udev rules
Probe at the given offset (only useful with -p).
Switch to low-level probing mode (bypass cache)
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.
Overwrite device/file size (only useful with -p).
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.
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.