1 .\" Copyright 2000 Andreas Dilger (adilger@turbolinux.com)
3 .\" This man page was created for blkid from e2fsprogs-1.25.
5 .\" This file may be copied under the terms of the GNU Public License.
7 .\" Based on uuidgen, Mon Sep 17 10:42:12 2000, Andreas Dilger
8 .TH BLKID 8 "February 2009" "Linux" "MAINTENANCE COMMANDS"
10 blkid \- command\-line utility to locate/print block device attributes
51 program is the command-line interface to working with
53 library. It can determine the type of content (e.g. filesystem, swap)
54 a block device holds, and also attributes (tokens, NAME=value pairs)
55 from the content metadata (e.g. LABEL or UUID fields).
58 has two main forms of operation: either searching for a device with a
59 specific NAME=value pair, or displaying NAME=value pairs for one or
66 instead of reading from the default cache file
68 If you want to start with a clean cache (i.e. don't report devices previously
69 scanned but not necessarily available at this time), specify
73 Perform a garbage collection pass on the blkid cache to remove
74 devices which no longer exist.
77 Display a usage message and exit.
80 Look up one device that matches the search parameter specified using
83 option. If there are multiple devices that match the specified search
84 parameter, then the device with the highest priority is returned, and/or
85 the first device found at a given priority. Device types in order of
86 decreasing priority are Device Mapper, EVMS, LVM, MD, and finally regular
87 block devices. If this option is not specified,
89 will print all of the devices that match the search parameter.
92 Look up one device that uses the label (same as: -l -o device -t
93 LABEL=<label>). This look up method is able to reliable use /dev/disk/by-label
94 udev symlinks (depends on setting in /etc/blkid.conf). Avoid to use the
95 symlinks directly. It is not reliable to use the symlinks without verification.
96 The \fB-L\fR option is portable and works on systems with and without udev.
99 Restrict probing functions to defined (comma separated) list of "usage" types.
100 Supported usage types are: filesystem, raid, crypto and other. The list can be
101 prefixed with "no" to specify the usage types which should be ignored. For example:
103 blkid -p -u filesystem,other /dev/sda1
105 probes for all filesystems and others (e.g. swap) formats, and
107 blkid -p -u noraid /dev/sda1
109 probes for all supported formats exclude RAIDs. This option is useful with
113 Look up one device that uses the uuid. For more details see the \fB-L\fR option.
118 output using the specified format. The
124 print all tags (the default)
127 print the value of the tags
130 print the devices in a user-friendly format
133 print the device name only
136 vol_id compatible mode; usable in udev rules
140 Probe at the given offset (only useful with \fB-p\fR).
143 Switch to low-level probing mode (bypass cache)"
146 For each (specified) device, show only the tags that match
148 It is possible to specify multiple
150 options. If no tag is specified, then all tokens are shown for all
152 In order to just refresh the cache without showing any tokens, use
154 with no other options.
157 Overwrite device/file size (only useful with \fB-p\fR).
159 .BI \-t " NAME" = "value"
160 Search for block devices with tokens named
164 and display any devices which are found.
172 If there are no devices specified on the command line, all block devices
173 will be searched; otherwise only the specified devices are searched.
176 Display version number and exit.
178 .BI \-w " writecachefile"
179 Write the device cache to
181 instead of writing it to the default cache file
183 If you don't want to save the cache to the default file, specify
185 If not specified it will be the same file as that given by the
190 Display tokens from only the specified device. It is possible to
193 options on the command line. If none is given, all devices which
196 are shown, if they are recognized.
198 If the specified token was found, or if any tags were shown from (specified)
199 devices, 0 is returned. If the specified token was not found, or no
200 (specified) devices could be identified, an exit code of 2 is returned.
201 For usage or other errors, an exit code of 4 is returned.
204 was written by Andreas Dilger for libblkid and improved by Theodore Ts'o
207 The blkid command is part of the util-linux-ng package and is available from
208 ftp://ftp.kernel.org/pub/linux/utils/util-linux-ng/.