1BLKID(8) MAINTENANCE COMMANDS BLKID(8)
2
6 blkid - command-line utility to locate/print block device attributes
7
9 blkid -L label | -U uuid
10 blkid [-ghlv] [-c file] [-w file] [-o format]
12 [-s tag] [-t NAME=value] device [device ...]
13 blkid -p [-O offset] [-S size] [-o format] [-s tag]
15 [-u list] device [device ...]
16 blkid -i [-o format] [-s tag] device [device ...]
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21 The blkid program is the command-line interface to working with lib‐
22 blkid(3) library. It can determine the type of content (e.g. filesys‐
23 tem, swap) a block device holds, and also attributes (tokens,
24 NAME=value pairs) from the content metadata (e.g. LABEL or UUID
25 fields).
26 Note that blkid reads information directly from devices and for non-
28 root users it returns cached unverified information. It is better to
29 use lsblk --fs to get a user-friendly overview of filesystems and
30 devices. lsblk(8) is also easy to use in scripts. blkid is mostly
31 designed for system services and to test libblkid functionality.
32 blkid does not read information about removable devices by default.
34 blkid has two main forms of operation: either searching for a device
36 with a specific NAME=value pair, or displaying NAME=value pairs for one
37 or more devices.
38
40 -c cachefile
41 Read from cachefile instead of reading from the default cache
42 file /etc/blkid/blkid.tab. If you want to start with a clean
43 cache (i.e. don't report devices previously scanned but not nec‐
44 essarily available at this time), specify /dev/null.
45 -g Perform a garbage collection pass on the blkid cache to remove
47 devices which no longer exist.
48 -h Display a usage message and exit.
50 -i Display I/O Limits (aka I/O topology) information. The 'export'
52 output format is automatically enabled. This option could be
53 used together with -p option.
54 -l Look up one device that matches the search parameter specified
56 using the -t option. If there are multiple devices that match
57 the specified search parameter, then the device with the highest
58 priority is returned, and/or the first device found at a given
59 priority. Device types in order of decreasing priority are
60 Device Mapper, EVMS, LVM, MD, and finally regular block devices.
61 If this option is not specified, blkid will print all of the
62 devices that match the search parameter.
63 -L label
65 Look up one device that uses the label (same as: -l -o device -t
66 LABEL=<label>). This look up method is able to reliable use
67 /dev/disk/by-label udev symlinks (depends on setting in
68 /etc/blkid.conf). Avoid to use the symlinks directly. It is not
69 reliable to use the symlinks without verification. The -L
70 option works on systems with and without udev.
71 Unfortunately, the original blkid(8) from e2fsprogs use the -L
73 option as a synonym to the -o list option. For better portabil‐
74 ity use "-l -o device -t LABEL=<label>" and "-o list" in your
75 scripts rather than -L option.
76 -u list
78 Restrict probing functions to defined (comma separated) list of
79 "usage" types. Supported usage types are: filesystem, raid,
80 crypto and other. The list can be prefixed with "no" to specify
81 the usage types which should be ignored. For example:
82 blkid -p -u filesystem,other /dev/sda1
84 probes for all filesystems and others (e.g. swap) formats, and
86 blkid -p -u noraid /dev/sda1
88 probes for all supported formats exclude RAIDs. This option is
90 useful with -p only.
91 -U uuid
93 Look up one device that uses the uuid. For more details see the
94 -L option.
95 -o format
97 Display blkid's output using the specified format. The format
98 parameter may be:
99 full print all tags (the default)
101 value print the value of the tags
103 list print the devices in a user-friendly format, this output
105 format is unsupported for low-level probing (-p or -i)
106 device print the device name only, this output format is always
108 enabled for -L and -U options
109 udev print key="value" pairs for easy import into the udev
111 environment
112 export print key=value pairs for easy import into the environ‐
114 ment. This output format is automatically enabled when
115 I/O Limits (-i option) are requested.
116 -O bytes
118 Probe at the given offset (only useful with -p). This option
119 could be used together with -i option.
120 -p Switch to low-level superblock probing mode (bypass cache).
122 -s tag For each (specified) device, show only the tags that match tag.
124 It is possible to specify multiple -s options. If no tag is
125 specified, then all tokens are shown for all (specified)
126 devices. In order to just refresh the cache without showing any
127 tokens, use -s none with no other options.
128 -S bytes
130 Overwrite device/file size (only useful with -p).
131 -t NAME=value
133 Search for block devices with tokens named NAME that have the
134 value value, and display any devices which are found. Common
135 values for NAME include TYPE, LABEL, and UUID. If there are no
136 devices specified on the command line, all block devices will be
137 searched; otherwise only the specified devices are searched.
138 -v Display version number and exit.
140 -w writecachefile
142 Write the device cache to writecachefile instead of writing it
143 to the default cache file.
144 This functionality has never been implemented and the option is
146 no more supported on the recent blkid versions (>= v2.21).
147 device Display tokens from only the specified device. It is possible
149 to give multiple device options on the command line. If none is
150 given, all devices which appear in /proc/partitions are shown,
151 if they are recognized.
152
154 If the specified token was found, or if any tags were shown from (spec‐
155 ified) devices, 0 is returned. If the specified token was not found,
156 or no (specified) devices could be identified, an exit code of 2 is
157 returned. For usage or other errors, an exit code of 4 is returned.
158
160 blkid was written by Andreas Dilger for libblkid and improved by
161 Theodore Ts'o and Karel Zak.
162
164 The blkid command is part of the util-linux-ng package and is available
165 from ftp://ftp.kernel.org/pub/linux/utils/util-linux-ng/.
166
168 libblkid(3) findfs(8) wipefs(8)
169Linux February 2009 BLKID(8)