1FSCK(8) System Administration FSCK(8)
2
6 fsck - check and repair a Linux filesystem
7
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 filesys‐
14 tems. filesys can be a device name (e.g. /dev/hdc1, /dev/sdb2), a
15 mount point (e.g. /, /usr, /home), or an ext2 label or UUID specifier
16 (e.g. UUID=8868abf6-88c5-4a83-98b8-bfc24057f7bd or LABEL=root). Nor‐
17 mally, the fsck program will try to handle filesystems on different
18 physical disk drives in parallel to reduce the total amount of time
19 needed to check all of them.
20 If no filesystems are specified on the command line, and the -A option
22 is not specified, fsck will default to checking filesystems in
23 /etc/fstab serially. This is equivalent to the -As options.
24 The exit code returned by fsck is the sum of the following conditions:
26 0 No errors
28 1 Filesystem errors corrected
29 2 System should be rebooted
30 4 Filesystem errors left uncorrected
31 8 Operational error
32 16 Usage or syntax error
33 32 Checking canceled by user request
34 128 Shared-library error
35 The exit code returned when multiple filesystems are checked is the
37 bit-wise OR of the exit codes for each filesystem that is checked.
38 In actuality, fsck is simply a front-end for the various filesystem
40 checkers (fsck.fstype) available under Linux. The filesystem-specific
41 checker is searched for in the PATH environment variable. If the PATH
42 is undefined then fallback to "/sbin".
43 Please see the filesystem-specific checker manual pages for further
45 details.
46
48 -l Create an exclusive flock(2) lock file
49 (/run/fsck/<diskname>.lock) for whole-disk device. This option
50 can be used with one device only (this means that -A and -l are
51 mutually exclusive). This option is recommended when more
52 fsck(8) instances are executed in the same time. The option is
53 ignored when used for multiple devices or for non-rotating
54 disks. fsck does not lock underlying devices when executed to
55 check stacked devices (e.g. MD or DM) – this feature is not
56 implemented yet.
57 -r [fd]
59 Report certain statistics for each fsck when it completes.
60 These statistics include the exit status, the maximum run set
61 size (in kilobytes), the elapsed all-clock time and the user and
62 system CPU time used by the fsck run. For example:
63 /dev/sda1: status 0, rss 92828, real 4.002804, user 2.677592,
65 sys 0.86186
66 GUI front-ends may specify a file descriptor fd, in which case
68 the progress bar information will be sent to that file descrip‐
69 tor in a machine parsable format. For example:
70 /dev/sda1 0 92828 4.002804 2.677592 0.86186
72 -s Serialize fsck operations. This is a good idea if you are
74 checking multiple filesystems and the checkers are in an inter‐
75 active mode. (Note: e2fsck(8) runs in an interactive mode by
76 default. To make e2fsck(8) run in a non-interactive mode, you
77 must either specify the -p or -a option, if you wish for errors
78 to be corrected automatically, or the -n option if you do not.)
79 -t fslist
81 Specifies the type(s) of filesystem to be checked. When the -A
82 flag is specified, only filesystems that match fslist are
83 checked. The fslist parameter is a comma-separated list of
84 filesystems and options specifiers. All of the filesystems in
85 this comma-separated list may be prefixed by a negation operator
86 'no' or '!', which requests that only those filesystems not
87 listed in fslist will be checked. If none of the filesystems in
88 fslist is prefixed by a negation operator, then only those
89 listed filesystems will be checked.
90 Options specifiers may be included in the comma-separated
92 fslist. They must have the format opts=fs-option. If an
93 options specifier is present, then only filesystems which con‐
94 tain fs-option in their mount options field of /etc/fstab will
95 be checked. If the options specifier is prefixed by a negation
96 operator, then only those filesystems that do not have fs-option
97 in their mount options field of /etc/fstab will be checked.
98 For example, if opts=ro appears in fslist, then only filesystems
100 listed in /etc/fstab with the ro option will be checked.
101 For compatibility with Mandrake distributions whose boot scripts
103 depend upon an unauthorized UI change to the fsck program, if a
104 filesystem type of loop is found in fslist, it is treated as if
105 opts=loop were specified as an argument to the -t option.
106 Normally, the filesystem type is deduced by searching for
108 filesys in the /etc/fstab file and using the corresponding
109 entry. If the type cannot be deduced, and there is only a sin‐
110 gle filesystem given as an argument to the -t option, fsck will
111 use the specified filesystem type. If this type is not avail‐
112 able, then the default filesystem type (currently ext2) is used.
113 -A Walk through the /etc/fstab file and try to check all filesys‐
115 tems in one run. This option is typically used from the /etc/rc
116 system initialization file, instead of multiple commands for
117 checking a single filesystem.
118 The root filesystem will be checked first unless the -P option
120 is specified (see below). After that, filesystems will be
121 checked in the order specified by the fs_passno (the sixth)
122 field in the /etc/fstab file. Filesystems with a fs_passno
123 value of 0 are skipped and are not checked at all. Filesystems
124 with a fs_passno value of greater than zero will be checked in
125 order, with filesystems with the lowest fs_passno number being
126 checked first. If there are multiple filesystems with the same
127 pass number, fsck will attempt to check them in parallel,
128 although it will avoid running multiple filesystem checks on the
129 same physical disk.
130 fsck does not check stacked devices (RAIDs, dm-crypt, ...) in
132 parallel with any other device. See below for
133 FSCK_FORCE_ALL_PARALLEL setting. The /sys filesystem is used to
134 determine dependencies between devices.
135 Hence, a very common configuration in /etc/fstab files is to set
137 the root filesystem to have a fs_passno value of 1 and to set
138 all other filesystems to have a fs_passno value of 2. This will
139 allow fsck to automatically run filesystem checkers in parallel
140 if it is advantageous to do so. System administrators might
141 choose not to use this configuration if they need to avoid mul‐
142 tiple filesystem checks running in parallel for some reason –
143 for example, if the machine in question is short on memory so
144 that excessive paging is a concern.
145 fsck normally does not check whether the device actually exists
147 before calling a filesystem specific checker. Therefore non-
148 existing devices may cause the system to enter filesystem repair
149 mode during boot if the filesystem specific checker returns a
150 fatal error. The /etc/fstab mount option nofail may be used to
151 have fsck skip non-existing devices. fsck also skips non-exist‐
152 ing devices that have the special filesystem type auto.
153 -C [fd]
155 Display completion/progress bars for those filesystem checkers
156 (currently only for ext[234]) which support them. fsck will
157 manage the filesystem checkers so that only one of them will
158 display a progress bar at a time. GUI front-ends may specify a
159 file descriptor fd, in which case the progress bar information
160 will be sent to that file descriptor.
161 -M Do not check mounted filesystems and return an exit code of 0
163 for mounted filesystems.
164 -N Don't execute, just show what would be done.
166 -P When the -A flag is set, check the root filesystem in parallel
168 with the other filesystems. This is not the safest thing in the
169 world to do, since if the root filesystem is in doubt things
170 like the e2fsck(8) executable might be corrupted! This option
171 is mainly provided for those sysadmins who don't want to repar‐
172 tition the root filesystem to be small and compact (which is
173 really the right solution).
174 -R When checking all filesystems with the -A flag, skip the root
176 filesystem. (This is useful in case the root filesystem has
177 already been mounted read-write.)
178 -T Don't show the title on startup.
180 -V Produce verbose output, including all filesystem-specific com‐
182 mands that are executed.
183 -?, --help
185 Display help text and exit.
186 --version
188 Display version information and exit.
189
191 Options which are not understood by fsck are passed to the filesystem-
192 specific checker!
193 These options must not take arguments, as there is no way for fsck to
195 be able to properly guess which options take arguments and which don't.
196 Options and arguments which follow the -- are treated as filesystem-
198 specific options to be passed to the filesystem-specific checker.
199 Please note that fsck is not designed to pass arbitrarily complicated
201 options to filesystem-specific checkers. If you're doing something
202 complicated, please just execute the filesystem-specific checker
203 directly. If you pass fsck some horribly complicated options and argu‐
204 ments, and it doesn't do what you expect, don't bother reporting it as
205 a bug. You're almost certainly doing something that you shouldn't be
206 doing with fsck. Options to different filesystem-specific fsck's are
207 not standardized.
208
210 /etc/fstab
211
213 The fsck program's behavior is affected by the following environment
214 variables:
215 FSCK_FORCE_ALL_PARALLEL
217 If this environment variable is set, fsck will attempt to check
218 all of the specified filesystems in parallel, regardless of
219 whether the filesystems appear to be on the same device. (This
220 is useful for RAID systems or high-end storage systems such as
221 those sold by companies such as IBM or EMC.) Note that the
222 fs_passno value is still used.
223 FSCK_MAX_INST
225 This environment variable will limit the maximum number of
226 filesystem checkers that can be running at one time. This
227 allows configurations which have a large number of disks to
228 avoid fsck starting too many filesystem checkers at once, which
229 might overload CPU and memory resources available on the system.
230 If this value is zero, then an unlimited number of processes can
231 be spawned. This is currently the default, but future versions
232 of fsck may attempt to automatically determine how many filesys‐
233 tem checks can be run based on gathering accounting data from
234 the operating system.
235 PATH The PATH environment variable is used to find filesystem check‐
237 ers.
238 FSTAB_FILE
240 This environment variable allows the system administrator to
241 override the standard location of the /etc/fstab file. It is
242 also useful for developers who are testing fsck.
243 LIBBLKID_DEBUG=all
245 enables libblkid debug output.
246 LIBMOUNT_DEBUG=all
248 enables libmount debug output.
249
251 fstab(5), mkfs(8), fsck.ext2(8) or fsck.ext3(8) or e2fsck(8), cramf‐
252 sck(8), fsck.jfs(8), fsck.nfs(8), fsck.minix(8), fsck.msdos(8),
253 fsck.vfat(8), fsck.xfs(8), reiserfsck(8)
254
256 Theodore Ts'o <tytso@mit.edu>
257 Karel Zak <kzak@redhat.com>
258
260 The fsck command is part of the util-linux package and is available
261 from Linux Kernel Archive ⟨https://www.kernel.org/pub/linux/utils/util-
262 linux/⟩.
263util-linux February 2009 FSCK(8)