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, --hint setting
85 Set probing hint. The hints are an optional way to force probing
86 functions to check, for example, another location. The currently
87 supported is "session_offset=number" to set session offset on
88 multi-session UDF.
89 -i, --info
91 Display information about I/O Limits (aka I/O topology). The
92 'export' output format is automatically enabled. This option can be
93 used together with the --probe option.
94 -k, --list-filesystems
96 List all known filesystems and RAIDs and exit.
97 -l, --list-one
99 Look up only one device that matches the search parameter specified
100 with the --match-token option. If there are multiple devices that
101 match the specified search parameter, then the device with the
102 highest priority is returned, and/or the first device found at a
103 given priority (but see below note about udev). Device types in
104 order of decreasing priority are: Device Mapper, EVMS, LVM, MD, and
105 finally regular block devices. If this option is not specified,
106 blkid will print all of the devices that match the search
107 parameter.
108 This option forces blkid to use udev when used for LABEL or UUID
110 tokens in --match-token. The goal is to provide output consistent
111 with other utils (like mount(8), etc.) on systems where the same
112 tag is used for multiple devices.
113 -L, --label label
115 Look up the device that uses this filesystem label; this is equal
116 to --list-one --output device --match-token LABEL=label. This
117 lookup method is able to reliably use /dev/disk/by-label udev
118 symlinks (dependent on a setting in /etc/blkid.conf). Avoid using
119 the symlinks directly; it is not reliable to use the symlinks
120 without verification. The --label option works on systems with and
121 without udev.
122 Unfortunately, the original blkid(8) from e2fsprogs uses the -L
124 option as a synonym for -o list. For better portability, use -l -o
125 device -t LABEL=label and -o list in your scripts rather than the
126 -L option.
127 -n, --match-types list
129 Restrict the probing functions to the specified (comma-separated)
130 list of superblock types (names). The list items may be prefixed
131 with "no" to specify the types which should be ignored. For
132 example:
133 blkid --probe --match-types vfat,ext3,ext4 /dev/sda1
135 probes for vfat, ext3 and ext4 filesystems, and
137 blkid --probe --match-types nominix /dev/sda1
139 probes for all supported formats except minix filesystems. This
141 option is only useful together with --probe.
142 -o, --output format
144 Use the specified output format. Note that the order of variables
145 and devices is not fixed. See also option -s. The format parameter
146 may be:
147 full
149 print all tags (the default)
150 value
152 print the value of the tags
153 list
155 print the devices in a user-friendly format; this output format
156 is unsupported for low-level probing (--probe or --info).
157 This output format is DEPRECATED in favour of the lsblk(8)
159 command.
160 device
162 print the device name only; this output format is always
163 enabled for the --label and --uuid options
164 udev
166 print key="value" pairs for easy import into the udev
167 environment; the keys are prefixed by ID_FS_ or ID_PART_
168 prefixes. The value may be modified to be safe for udev
169 environment; allowed is plain ASCII, hex-escaping and valid
170 UTF-8, everything else (including whitespaces) is replaced with
171 '_'. The keys with _ENC postfix use hex-escaping for unsafe
172 chars.
173 The udev output returns the ID_FS_AMBIVALENT tag if more
175 superblocks are detected, and ID_PART_ENTRY_* tags are always
176 returned for all partitions including empty partitions.
177 This output format is DEPRECATED.
179 export
181 print key=value pairs for easy import into the environment;
182 this output format is automatically enabled when I/O Limits
183 (--info option) are requested.
184 The non-printing characters are encoded by ^ and M- notation
186 and all potentially unsafe characters are escaped.
187 -O, --offset offset
189 Probe at the given offset (only useful with --probe). This option
190 can be used together with the --info option.
191 -p, --probe
193 Switch to low-level superblock probing mode (bypassing the cache).
194 Note that low-level probing also returns information about
196 partition table type (PTTYPE tag) and partitions (PART_ENTRY_*
197 tags). The tag names produced by low-level probing are based on
198 names used internally by libblkid and it may be different than when
199 executed without --probe (for example PART_ENTRY_UUID= vs
200 PARTUUID=). See also --no-part-details.
201 -s, --match-tag tag
203 For each (specified) device, show only the tags that match tag. It
204 is possible to specify multiple --match-tag options. If no tag is
205 specified, then all tokens are shown for all (specified) devices.
206 In order to just refresh the cache without showing any tokens, use
207 --match-tag none with no other options.
208 -S, --size size
210 Override the size of device/file (only useful with --probe).
211 -t, --match-token NAME=value
213 Search for block devices with tokens named NAME that have the value
214 value, and display any devices which are found. Common values for
215 NAME include TYPE, LABEL, and UUID. If there are no devices
216 specified on the command line, all block devices will be searched;
217 otherwise only the specified devices are searched.
218 -u, --usages list
220 Restrict the probing functions to the specified (comma-separated)
221 list of "usage" types. Supported usage types are: filesystem, raid,
222 crypto and other. The list items may be prefixed with "no" to
223 specify the usage types which should be ignored. For example:
224 blkid --probe --usages filesystem,other /dev/sda1
226 probes for all filesystem and other (e.g., swap) formats, and
228 blkid --probe --usages noraid /dev/sda1
230 probes for all supported formats except RAIDs. This option is only
232 useful together with --probe.
233 -U, --uuid uuid
235 Look up the device that uses this filesystem uuid. For more details
236 see the --label option.
237 -h, --help
239 Display help text and exit.
240 -V, --version
242 Print version 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/util-linux/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 2.38 2022-02-17 BLKID(8)