The
blkid
program is the command-line interface to working with
libuuid(3)
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).
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 devices.
OPTIONS
-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.
-h
Display a usage message and exit.
-p
Probe all available devices. This is the default when displaying
tokens. When searching for a token normally the cache file is
used to locate the device and only that device is probed (to ensure
cache coherency) and all devices are probed only if the token cannot
be found in the cache.
-s
tagtag
is of the form
NAME
and the resulting token is shown for each (specified) device that has
such a tag. It is possible to specify multiple
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
-s none
with no other options.
-t
tokentoken
is of the form
NAME=value
and that specific token is searched for in the cache or among all visible
block devices and additionally any specified devices. If that token is
not found, no output is shown. Common values for
NAME
include
TYPE,
LABEL,
and
UUID.
-v
Display version number and exit.
RETURN VALUE
The UUID of the form 1b4e28ba-2fa1-11d2-883f-b9a761bde3fb (in
printf(3)
format "%08x-%04x-%04x-%04x-%012x") is output to the standard output.
-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 to the default file, specify
/dev/null.
If not specified it will be the same file as that given by 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 return 2. For usage or other errors
return 4.