.\" 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 "@E2FSPROGS_MONTH@ @E2FSPROGS_YEAR@" "E2fsprogs version @E2FSPROGS_VERSION@"
.SH NAME
blkid \- command\-line utility to locate/print block device attributes
.SH SYNOPSIS
.B blkid 
[
.B \-hlv
]
[
[
.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 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).
.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
.B \-c
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 \-h
Display a usage message and exit.
.TP
.B \-l
Look up the device that matches the search parameter specified using
the 
.B \-t
option, assuming that there is only one matching the search parameter.  
For a system with a large number of disks, this will be more 
efficient by avoiding the need to revalidate devices unless absolutely 
necessary.  If this option is not specified, 
.B blkid
will use a less efficient approach, which allows 
.B blkid
to print all of the devices that match the search parameter.
.IP
This option is best used for tag searches such as 
.I LABEL=data_vol
or
.IR UUID=e280469a-d06f-4c0b-b068-44f3b576029e .
If you want 
.B blkid
to print all of the ext3 filesystems using a search parameter 
such as
.IR TYPE=ext3 ,
then this option should 
.I not
be used.
.TP
.B \-o 
Display 
.BR blkid 's
output using the specified format.  The
.I format
parameter may be 
.IR full ,
(the default), 
.IR  value ,
(only print the value of any tags printed by 
.BR blkid)
or 
.I device
(only print the device name).
.TP
.B \-s
Show only the tags for each (specified) device 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
.B \-t
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 search the devices specified by the user.
.TP
.B \-v
Display version number and exit.
.TP
.B \-w
.I <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)