.\" Copyright 2000 Andreas Dilger (adilger@turbolinux.com)
.\"
.\" This man page was created for blkid from e2fsprogs-1.25.
.\"
.\" This file may be copied under the terms of the GNU Public License.
.\"
.\" Based on uuidgen, Mon Sep 17 10:42:12 2000, Andreas Dilger
.TH BLKID 8 "September 2019" "E2fsprogs version 1.45.4"
.SH NAME
blkid \- command\-line utility to locate/print block device attributes
.SH SYNOPSIS
.B blkid
[
.B \-ghlLv
]
[
[
.B \-c
.I cachefile
]
.B \-w
.I writecachefile
]
[
.B \-o
.I format
]
[
.B \-s
.I tag
]
[
.B \-t
.IR NAME = value
]
[
.I device ...
]
.SH DESCRIPTION
The
.B blkid
program is the command-line interface to working with
.BR libblkid (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).
.PP
.B 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.
.SH OPTIONS
.TP
.BI \-c " cachefile"
Read from
.I cachefile
instead of reading from the default cache file
.IR /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
.IR /dev/null .
.TP
.B \-g
Perform a garbage collection pass on the blkid cache to remove
devices which no longer exist.
.TP
.B \-h
Display a usage message and exit.
.TP
.B \-l
Look up one device that matches the search parameter specified using
the
.B \-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,
.B blkid
will print all of the devices that match the search parameter.
.TP
.BI \-o " format"
Display
.BR blkid 's
output using the specified format.  The
.I format
parameter may be
.I full
(the default),
.I value
(only print the value of the tags),
.I list
(print the devices in a user-friendly format),
or
.I device
(only print the device name).
.TP
.B \-L
Print the devices in a user-friendly list format.  This is the
equivalent of using the option \fB-o list\fR.
.TP
.BI \-s " tag"
For each (specified) device, show only the tags that match
.IR tag .
It is possible to specify multiple
.B \-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
.B "-s none"
with no other options.
.TP
.BI \-t " NAME" = "value"
Search for block devices with tokens named
.I NAME
that have the value
.IR value ,
and display any devices which are found.
Common values for
.I NAME
include
.BR TYPE ,
.BR LABEL ,
and
.BR UUID .
If there are no devices specified on the command line, all block devices
will be searched; otherwise only the specified devices are searched.
.TP
.B \-v
Display version number and exit.
.TP
.BI \-w " writecachefile"
Write the device cache to
.I writecachefile
instead of writing it to the default cache file
.IR /etc/blkid.tab .
If you don't want to save the cache to the default file, specify
.IR /dev/null.
If not specified it will be the same file as that given by the
.B \-c
option.
.TP
.I device
Display tokens from only the specified device.  It is possible to
give multiple
.I device
options on the command line.  If none is given, all devices which
appear in
.I /proc/partitions
are shown, if they are recognized.
.SH "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.
.SH AUTHOR
.B blkid
was written by Andreas Dilger for libblkid.
.SH AVAILABILITY
.B blkid
is part the e2fsprogs package since version 1.26 and is available from
http://e2fsprogs.sourceforge.net.
.SH "SEE ALSO"
.BR libblkid (3)