1FSCK(8) System Administration FSCK(8)
2
6 fsck - check and repair a Linux filesystem
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9 fsck [-lsAVRTMNP] [-r [fd]] [-C [fd]] [-t fstype] [filesystem...] [--]
10 [fs-specific-options]
11
13 fsck is used to check and optionally repair one or more Linux
14 filesystems. filesystem can be a device name (e.g., /dev/hdc1,
15 /dev/sdb2), a mount point (e.g., /, /usr, /home), or an filesystem
16 label or UUID specifier (e.g.,
17 UUID=8868abf6-88c5-4a83-98b8-bfc24057f7bd or LABEL=root). Normally, the
18 fsck program will try to handle filesystems on different physical disk
19 drives in parallel to reduce the total amount of time needed to check
20 all of them.
21 If no filesystems are specified on the command line, and the -A option
23 is not specified, fsck will default to checking filesystems in
24 /etc/fstab serially. This is equivalent to the -As options.
25 The exit status returned by fsck is the sum of the following
27 conditions:
28 0
30 No errors
31 1
33 Filesystem errors corrected
34 2
36 System should be rebooted
37 4
39 Filesystem errors left uncorrected
40 8
42 Operational error
43 16
45 Usage or syntax error
46 32
48 Checking canceled by user request
49 128
51 Shared-library error
52 The exit status returned when multiple filesystems are checked is the
54 bit-wise OR of the exit statuses for each filesystem that is checked.
55 In actuality, fsck is simply a front-end for the various filesystem
57 checkers (fsck.fstype) available under Linux. The filesystem-specific
58 checker is searched for in the PATH environment variable. If the PATH
59 is undefined then fallback to /sbin.
60 Please see the filesystem-specific checker manual pages for further
62 details.
63
65 -l
66 Create an exclusive flock(2) lock file (/run/fsck/<diskname>.lock)
67 for whole-disk device. This option can be used with one device only
68 (this means that -A and -l are mutually exclusive). This option is
69 recommended when more fsck instances are executed in the same time.
70 The option is ignored when used for multiple devices or for
71 non-rotating disks. fsck does not lock underlying devices when
72 executed to check stacked devices (e.g. MD or DM) - this feature is
73 not implemented yet.
74 -r [fd]
76 Report certain statistics for each fsck when it completes. These
77 statistics include the exit status, the maximum run set size (in
78 kilobytes), the elapsed all-clock time and the user and system CPU
79 time used by the fsck run. For example:
80 /dev/sda1: status 0, rss 92828, real 4.002804, user 2.677592, sys
82 0.86186
83 GUI front-ends may specify a file descriptor fd, in which case the
85 progress bar information will be sent to that file descriptor in a
86 machine parsable format. For example:
87 /dev/sda1 0 92828 4.002804 2.677592 0.86186
89 -s
91 Serialize fsck operations. This is a good idea if you are checking
92 multiple filesystems and the checkers are in an interactive mode.
93 (Note: e2fsck(8) runs in an interactive mode by default. To make
94 e2fsck(8) run in a non-interactive mode, you must either specify
95 the -p or -a option, if you wish for errors to be corrected
96 automatically, or the -n option if you do not.)
97 -t fslist
99 Specifies the type(s) of filesystem to be checked. When the -A flag
100 is specified, only filesystems that match fslist are checked. The
101 fslist parameter is a comma-separated list of filesystems and
102 options specifiers. All of the filesystems in this comma-separated
103 list may be prefixed by a negation operator 'no' or '!', which
104 requests that only those filesystems not listed in fslist will be
105 checked. If none of the filesystems in fslist is prefixed by a
106 negation operator, then only those listed filesystems will be
107 checked.
108 Options specifiers may be included in the comma-separated fslist.
110 They must have the format opts=fs-option. If an options specifier
111 is present, then only filesystems which contain fs-option in their
112 mount options field of /etc/fstab will be checked. If the options
113 specifier is prefixed by a negation operator, then only those
114 filesystems that do not have fs-option in their mount options field
115 of /etc/fstab will be checked.
116 For example, if opts=ro appears in fslist, then only filesystems
118 listed in /etc/fstab with the ro option will be checked.
119 For compatibility with Mandrake distributions whose boot scripts
121 depend upon an unauthorized UI change to the fsck program, if a
122 filesystem type of loop is found in fslist, it is treated as if
123 opts=loop were specified as an argument to the -t option.
124 Normally, the filesystem type is deduced by searching for filesys
126 in the /etc/fstab file and using the corresponding entry. If the
127 type cannot be deduced, and there is only a single filesystem given
128 as an argument to the -t option, fsck will use the specified
129 filesystem type. If this type is not available, then the default
130 filesystem type (currently ext2) is used.
131 -A
133 Walk through the /etc/fstab file and try to check all filesystems
134 in one run. This option is typically used from the /etc/rc system
135 initialization file, instead of multiple commands for checking a
136 single filesystem.
137 The root filesystem will be checked first unless the -P option is
139 specified (see below). After that, filesystems will be checked in
140 the order specified by the fs_passno (the sixth) field in the
141 /etc/fstab file. Filesystems with a fs_passno value of 0 are
142 skipped and are not checked at all. Filesystems with a fs_passno
143 value of greater than zero will be checked in order, with
144 filesystems with the lowest fs_passno number being checked first.
145 If there are multiple filesystems with the same pass number, fsck
146 will attempt to check them in parallel, although it will avoid
147 running multiple filesystem checks on the same physical disk.
148 fsck does not check stacked devices (RAIDs, dm-crypt, ...) in
150 parallel with any other device. See below for
151 FSCK_FORCE_ALL_PARALLEL setting. The /sys filesystem is used to
152 determine dependencies between devices.
153 Hence, a very common configuration in /etc/fstab files is to set
155 the root filesystem to have a fs_passno value of 1 and to set all
156 other filesystems to have a fs_passno value of 2. This will allow
157 fsck to automatically run filesystem checkers in parallel if it is
158 advantageous to do so. System administrators might choose not to
159 use this configuration if they need to avoid multiple filesystem
160 checks running in parallel for some reason - for example, if the
161 machine in question is short on memory so that excessive paging is
162 a concern.
163 fsck normally does not check whether the device actually exists
165 before calling a filesystem specific checker. Therefore
166 non-existing devices may cause the system to enter filesystem
167 repair mode during boot if the filesystem specific checker returns
168 a fatal error. The /etc/fstab mount option nofail may be used to
169 have fsck skip non-existing devices. fsck also skips non-existing
170 devices that have the special filesystem type auto.
171 -C [fd]
173 Display completion/progress bars for those filesystem checkers
174 (currently only for ext[234]) which support them. fsck will manage
175 the filesystem checkers so that only one of them will display a
176 progress bar at a time. GUI front-ends may specify a file
177 descriptor fd, in which case the progress bar information will be
178 sent to that file descriptor.
179 -M
181 Do not check mounted filesystems and return an exit status of 0 for
182 mounted filesystems.
183 -N
185 Don’t execute, just show what would be done.
186 -P
188 When the -A flag is set, check the root filesystem in parallel with
189 the other filesystems. This is not the safest thing in the world to
190 do, since if the root filesystem is in doubt things like the
191 e2fsck(8) executable might be corrupted! This option is mainly
192 provided for those sysadmins who don’t want to repartition the root
193 filesystem to be small and compact (which is really the right
194 solution).
195 -R
197 When checking all filesystems with the -A flag, skip the root
198 filesystem. (This is useful in case the root filesystem has already
199 been mounted read-write.)
200 -T
202 Don’t show the title on startup.
203 -V
205 Produce verbose output, including all filesystem-specific commands
206 that are executed.
207 -?, --help
209 Display help text and exit.
210 --version
212 Display version information and exit.
213
215 Options which are not understood by fsck are passed to the
216 filesystem-specific checker!
217 These options must not take arguments, as there is no way for fsck to
219 be able to properly guess which options take arguments and which don’t.
220 Options and arguments which follow the -- are treated as
222 filesystem-specific options to be passed to the filesystem-specific
223 checker.
224 Please note that fsck is not designed to pass arbitrarily complicated
226 options to filesystem-specific checkers. If you’re doing something
227 complicated, please just execute the filesystem-specific checker
228 directly. If you pass fsck some horribly complicated options and
229 arguments, and it doesn’t do what you expect, don’t bother reporting it
230 as a bug. You’re almost certainly doing something that you shouldn’t be
231 doing with fsck. Options to different filesystem-specific fsck’s are
232 not standardized.
233
235 The fsck program’s behavior is affected by the following environment
236 variables:
237 FSCK_FORCE_ALL_PARALLEL
239 If this environment variable is set, fsck will attempt to check all
240 of the specified filesystems in parallel, regardless of whether the
241 filesystems appear to be on the same device. (This is useful for
242 RAID systems or high-end storage systems such as those sold by
243 companies such as IBM or EMC.) Note that the fs_passno value is
244 still used.
245 FSCK_MAX_INST
247 This environment variable will limit the maximum number of
248 filesystem checkers that can be running at one time. This allows
249 configurations which have a large number of disks to avoid fsck
250 starting too many filesystem checkers at once, which might overload
251 CPU and memory resources available on the system. If this value is
252 zero, then an unlimited number of processes can be spawned. This is
253 currently the default, but future versions of fsck may attempt to
254 automatically determine how many filesystem checks can be run based
255 on gathering accounting data from the operating system.
256 PATH
258 The PATH environment variable is used to find filesystem checkers.
259 FSTAB_FILE
261 This environment variable allows the system administrator to
262 override the standard location of the /etc/fstab file. It is also
263 useful for developers who are testing fsck.
264 LIBBLKID_DEBUG=all
266 enables libblkid debug output.
267 LIBMOUNT_DEBUG=all
269 enables libmount debug output.
270
272 /etc/fstab
273
275 Theodore Ts’o <tytso@mit.edu>>, Karel Zak <kzak@redhat.com>
276
278 fstab(5), mkfs(8), fsck.ext2(8) or fsck.ext3(8) or e2fsck(8),
279 fsck.cramfs(8), fsck.jfs(8), fsck.nfs(8), fsck.minix(8), fsck.msdos(8),
280 fsck.vfat(8), fsck.xfs(8), reiserfsck(8)
281
283 For bug reports, use the issue tracker at
284 https://github.com/util-linux/util-linux/issues.
285
287 The fsck command is part of the util-linux package which can be
288 downloaded from Linux Kernel Archive
289 <https://www.kernel.org/pub/linux/utils/util-linux/>.
290util-linux 2.38.1 2022-05-11 FSCK(8)