blkid
locate/print block device attributes
see also :
findfs - wipefs
Synopsis
blkid
-L label | -U uuid
blkid
[-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 ...
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examples
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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/sda1
probes for
vfat, ext3 and ext4 filesystems, and
blkid -p -n
nominix /dev/sda1
probes 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/sda1
probes for all
filesystem and other (e.g. swap) formats, and
blkid -p -u
noraid /dev/sda1
probes 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.
availability
The blkid command is part of the util-linux package and is
available from ftp://ftp.kernel.org/pub/linux/utils/util-linux/.
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.
see also
libblkid
findfs wipefs
author
blkid
was written by Andreas Dilger for libblkid and improved by
Theodore Ts’o and Karel Zak.