1BLKID(8) System Administration BLKID(8)
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6 blkid - locate/print block device attributes
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9 blkid --label label | --uuid uuid
10 blkid [--no-encoding --garbage-collect --list-one --cache-file file]
12 [--output format] [--match-tag tag] [--match-token NAME=value]
13 [device...]
14 blkid --probe [--offset offset] [--output format] [--size size]
16 [--match-tag tag] [--match-types list] [--usages list]
17 [--no-part-details] device...
18 blkid --info [--output format] [--match-tag tag] device...
20
22 The blkid program is the command-line interface to working with the
23 libblkid(3) library. It can determine the type of content (e.g.,
24 filesystem or swap) that a block device holds, and also the attributes
25 (tokens, NAME=value pairs) from the content metadata (e.g., LABEL or
26 UUID fields).
27 It is recommended to use lsblk(8) command to get information about
29 block devices, or lsblk --fs to get an overview of filesystems, or
30 findmnt(8) to search in already mounted filesystems.
31 lsblk(8) provides more information, better control on output
33 formatting, easy to use in scripts and it does not require
34 root permissions to get actual information. blkid reads
35 information directly from devices and for non-root users it
36 returns cached unverified information. blkid is mostly
37 designed for system services and to test libblkid(3)
38 functionality.
39 When device is specified, tokens from only this device are displayed.
41 It is possible to specify multiple device arguments on the command
42 line. If none is given, all partitions or unpartitioned devices which
43 appear in /proc/partitions are shown, if they are recognized.
44 blkid has two main forms of operation: either searching for a device
46 with a specific NAME=value pair, or displaying NAME=value pairs for one
47 or more specified devices.
48 For security reasons blkid silently ignores all devices where the
50 probing result is ambivalent (multiple colliding filesystems are
51 detected). The low-level probing mode (-p) provides more information
52 and extra exit status in this case. It’s recommended to use wipefs(8)
53 to get a detailed overview and to erase obsolete stuff (magic strings)
54 from the device.
55
57 The size and offset arguments may be followed by the multiplicative
58 suffixes like KiB (=1024), MiB (=1024*1024), and so on for GiB, TiB,
59 PiB, EiB, ZiB and YiB (the "iB" is optional, e.g., "K" has the same
60 meaning as "KiB"), or the suffixes KB (=1000), MB (=1000*1000), and so
61 on for GB, TB, PB, EB, ZB and YB.
62 -c, --cache-file cachefile
64 Read from cachefile instead of reading from the default cache file
65 (see the CONFIGURATION FILE section for more details). If you want
66 to start with a clean cache (i.e., don’t report devices previously
67 scanned but not necessarily available at this time), specify
68 /dev/null.
69 -d, --no-encoding
71 Don’t encode non-printing characters. The non-printing characters
72 are encoded by ^ and M- notation by default. Note that the --output
73 udev output format uses a different encoding which cannot be
74 disabled.
75 -D, --no-part-details
77 Don’t print information (PART_ENTRY_* tags) from partition table in
78 low-level probing mode.
79 -g, --garbage-collect
81 Perform a garbage collection pass on the blkid cache to remove
82 devices which no longer exist.
83 -h, --help
85 Display a usage message and exit.
86 -H, --hint setting
88 Set probing hint. The hints are optional way how to force probing
89 functions to check for example another location. The currently
90 supported is "session_offset=number" to set session offset on
91 multi-session UDF.
92 -i, --info
94 Display information about I/O Limits (aka I/O topology). The
95 'export' output format is automatically enabled. This option can be
96 used together with the --probe option.
97 -k, --list-filesystems
99 List all known filesystems and RAIDs and exit.
100 -l, --list-one
102 Look up only one device that matches the search parameter specified
103 with the --match-token option. If there are multiple devices that
104 match the specified search parameter, then the device with the
105 highest priority is returned, and/or the first device found at a
106 given priority (but see below note about udev). Device types in
107 order of decreasing priority are: Device Mapper, EVMS, LVM, MD, and
108 finally regular block devices. If this option is not specified,
109 blkid will print all of the devices that match the search
110 parameter.
111 This option forces blkid to use udev when used for LABEL or UUID
113 tokens in --match-token. The goal is to provide output consistent
114 with other utils (like mount(8), etc.) on systems where the same
115 tag is used for multiple devices.
116 -L, --label label
118 Look up the device that uses this filesystem label; this is equal
119 to --list-one --output device --match-token LABEL=label. This
120 lookup method is able to reliably use /dev/disk/by-label udev
121 symlinks (dependent on a setting in /etc/blkid.conf). Avoid using
122 the symlinks directly; it is not reliable to use the symlinks
123 without verification. The --label option works on systems with and
124 without udev.
125 Unfortunately, the original blkid(8) from e2fsprogs uses the -L
127 option as a synonym for -o list. For better portability, use -l -o
128 device -t LABEL=label and -o list in your scripts rather than the
129 -L option.
130 -n, --match-types list
132 Restrict the probing functions to the specified (comma-separated)
133 list of superblock types (names). The list items may be prefixed
134 with "no" to specify the types which should be ignored. For
135 example:
136 blkid --probe --match-types vfat,ext3,ext4 /dev/sda1
138 probes for vfat, ext3 and ext4 filesystems, and
140 blkid --probe --match-types nominix /dev/sda1
142 probes for all supported formats except minix filesystems. This
144 option is only useful together with --probe.
145 -o, --output format
147 Use the specified output format. Note that the order of variables
148 and devices is not fixed. See also option -s. The format parameter
149 may be:
150 full
152 print all tags (the default)
153 value
155 print the value of the tags
156 list
158 print the devices in a user-friendly format; this output format
159 is unsupported for low-level probing (--probe or --info).
160 This output format is DEPRECATED in favour of the lsblk(8)
162 command.
163 device
165 print the device name only; this output format is always
166 enabled for the --label and --uuid options
167 udev
169 print key="value" pairs for easy import into the udev
170 environment; the keys are prefixed by ID_FS_ or ID_PART_
171 prefixes. The value may be modified to be safe for udev
172 environment; allowed is plain ASCII, hex-escaping and valid
173 UTF-8, everything else (including whitespaces) is replaced with
174 '_'. The keys with _ENC postfix use hex-escaping for unsafe
175 chars.
176 The udev output returns the ID_FS_AMBIVALENT tag if more
178 superblocks are detected, and ID_PART_ENTRY_* tags are always
179 returned for all partitions including empty partitions.
180 This output format is DEPRECATED.
182 export
184 print key=value pairs for easy import into the environment;
185 this output format is automatically enabled when I/O Limits
186 (--info option) are requested.
187 The non-printing characters are encoded by ^ and M- notation
189 and all potentially unsafe characters are escaped.
190 -O, --offset offset
192 Probe at the given offset (only useful with --probe). This option
193 can be used together with the --info option.
194 -p, --probe
196 Switch to low-level superblock probing mode (bypassing the cache).
197 Note that low-level probing also returns information about
199 partition table type (PTTYPE tag) and partitions (PART_ENTRY_*
200 tags). The tag names produced by low-level probing are based on
201 names used internally by libblkid and it may be different than when
202 executed without --probe (for example PART_ENTRY_UUID= vs
203 PARTUUID=). See also --no-part-details.
204 -s, --match-tag tag
206 For each (specified) device, show only the tags that match tag. It
207 is possible to specify multiple --match-tag options. If no tag is
208 specified, then all tokens are shown for all (specified) devices.
209 In order to just refresh the cache without showing any tokens, use
210 --match-tag none with no other options.
211 -S, --size size
213 Override the size of device/file (only useful with --probe).
214 -t, --match-token NAME=value
216 Search for block devices with tokens named NAME that have the value
217 value, and display any devices which are found. Common values for
218 NAME include TYPE, LABEL, and UUID. If there are no devices
219 specified on the command line, all block devices will be searched;
220 otherwise only the specified devices are searched.
221 -u, --usages list
223 Restrict the probing functions to the specified (comma-separated)
224 list of "usage" types. Supported usage types are: filesystem, raid,
225 crypto and other. The list items may be prefixed with "no" to
226 specify the usage types which should be ignored. For example:
227 blkid --probe --usages filesystem,other /dev/sda1
229 probes for all filesystem and other (e.g., swap) formats, and
231 blkid --probe --usages noraid /dev/sda1
233 probes for all supported formats except RAIDs. This option is only
235 useful together with --probe.
236 -U, --uuid uuid
238 Look up the device that uses this filesystem uuid. For more details
239 see the --label option.
240 -V, --version
242 Display version number and exit.
243
245 If the specified device or device addressed by specified token (option
246 --match-token) was found and it’s possible to gather any information
247 about the device, an exit status 0 is returned. Note the option
248 --match-tag filters output tags, but it does not affect exit status.
249 If the specified token was not found, or no (specified) devices could
251 be identified, or it is impossible to gather any information about the
252 device identifiers or device content an exit status of 2 is returned.
253 For usage or other errors, an exit status of 4 is returned.
255 If an ambivalent probing result was detected by low-level probing mode
257 (-p), an exit status of 8 is returned.
258
260 The standard location of the /etc/blkid.conf config file can be
261 overridden by the environment variable BLKID_CONF. The following
262 options control the libblkid library:
263 SEND_UEVENT=<yes|not>
265 Sends uevent when /dev/disk/by-{label,uuid,partuuid,partlabel}/
266 symlink does not match with LABEL, UUID, PARTUUID or PARTLABEL on
267 the device. Default is "yes".
268 CACHE_FILE=<path>
270 Overrides the standard location of the cache file. This setting can
271 be overridden by the environment variable BLKID_FILE. Default is
272 /run/blkid/blkid.tab, or /etc/blkid.tab on systems without a /run
273 directory.
274 EVALUATE=<methods>
276 Defines LABEL and UUID evaluation method(s). Currently, the
277 libblkid library supports the "udev" and "scan" methods. More than
278 one method may be specified in a comma-separated list. Default is
279 "udev,scan". The "udev" method uses udev /dev/disk/by-* symlinks
280 and the "scan" method scans all block devices from the
281 /proc/partitions file.
282
284 Setting LIBBLKID_DEBUG=all enables debug output.
285
287 blkid was written by Andreas Dilger for libblkid and improved by
288 Theodore Ts’o and Karel Zak.
289
291 libblkid(3), findfs(8), lsblk(8), wipefs(8)
292
294 For bug reports, use the issue tracker at
295 https://github.com/karelzak/util-linux/issues.
296
298 The blkid command is part of the util-linux package which can be
299 downloaded from Linux Kernel Archive
300 <https://www.kernel.org/pub/linux/utils/util-linux/>.
301util-linux 2.37.2 2021-07-20 BLKID(8)