1FSCK(8) System Administration FSCK(8)
2
6 fsck - check and repair a Linux filesystem
7
9 fsck [-lrsAVRTMNP] [-C [fd]] [-t fstype] [filesystem...] [--] [fs-spe‐
10 cific-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 /sbin first, then in /etc/fs and /etc, and
42 finally in the directories listed in the PATH environment variable.
43 Please see the filesystem-specific checker manual pages for further
44 details.
45
47 -l Lock the whole-disk device by an exclusive flock(2). This
48 option can be used with one device only (this means that -A and
49 -l are mutually exclusive). This option is recommended when
50 more fsck(8) instances are executed in the same time. The
51 option is ignored when used for multiple devices or for non-
52 rotating disks. fsck does not lock underlying devices when exe‐
53 cuted to check stacked devices (e.g. MD or DM) -- this feature
54 is not implemented yet.
55 -r Report certain statistics for each fsck when it completes. These
57 statistics include the exit status, the maximum run set size (in
58 kilobytes), the elapsed all-clock time and the user and system
59 CPU time used by the fsck run. For example:
60 /dev/sda1: status 0, rss 92828, real 4.002804, user 2.677592,
62 sys 0.86186
63 -s Serialize fsck operations. This is a good idea if you are
65 checking multiple filesystems and the checkers are in an inter‐
66 active mode. (Note: e2fsck(8) runs in an interactive mode by
67 default. To make e2fsck(8) run in a non-interactive mode, you
68 must either specify the -p or -a option, if you wish for errors
69 to be corrected automatically, or the -n option if you do not.)
70 -t fslist
72 Specifies the type(s) of filesystem to be checked. When the -A
73 flag is specified, only filesystems that match fslist are
74 checked. The fslist parameter is a comma-separated list of
75 filesystems and options specifiers. All of the filesystems in
76 this comma-separated list may be prefixed by a negation operator
77 'no' or '!', which requests that only those filesystems not
78 listed in fslist will be checked. If none of the filesystems in
79 fslist is prefixed by a negation operator, then only those
80 listed filesystems will be checked.
81 Options specifiers may be included in the comma-separated
83 fslist. They must have the format opts=fs-option. If an
84 options specifier is present, then only filesystems which con‐
85 tain fs-option in their mount options field of /etc/fstab will
86 be checked. If the options specifier is prefixed by a negation
87 operator, then only those filesystems that do not have fs-option
88 in their mount options field of /etc/fstab will be checked.
89 For example, if opts=ro appears in fslist, then only filesystems
91 listed in /etc/fstab with the ro option will be checked.
92 For compatibility with Mandrake distributions whose boot scripts
94 depend upon an unauthorized UI change to the fsck program, if a
95 filesystem type of loop is found in fslist, it is treated as if
96 opts=loop were specified as an argument to the -t option.
97 Normally, the filesystem type is deduced by searching for
99 filesys in the /etc/fstab file and using the corresponding
100 entry. If the type can not be deduced, and there is only a sin‐
101 gle filesystem given as an argument to the -t option, fsck will
102 use the specified filesystem type. If this type is not avail‐
103 able, then the default filesystem type (currently ext2) is used.
104 -A Walk through the /etc/fstab file and try to check all filesys‐
106 tems in one run. This option is typically used from the /etc/rc
107 system initialization file, instead of multiple commands for
108 checking a single filesystem.
109 The root filesystem will be checked first unless the -P option
111 is specified (see below). After that, filesystems will be
112 checked in the order specified by the fs_passno (the sixth)
113 field in the /etc/fstab file. Filesystems with a fs_passno
114 value of 0 are skipped and are not checked at all. Filesystems
115 with a fs_passno value of greater than zero will be checked in
116 order, with filesystems with the lowest fs_passno number being
117 checked first. If there are multiple filesystems with the same
118 pass number, fsck will attempt to check them in parallel,
119 although it will avoid running multiple filesystem checks on the
120 same physical disk.
121 fsck does not check stacked devices (RAIDs, dm-crypt, ...) in
123 parallel with any other device. See below for
124 FSCK_FORCE_ALL_PARALLEL setting. The /sys filesystem is used to
125 detemine dependencies between devices.
126 Hence, a very common configuration in /etc/fstab files is to set
128 the root filesystem to have a fs_passno value of 1 and to set
129 all other filesystems to have a fs_passno value of 2. This will
130 allow fsck to automatically run filesystem checkers in parallel
131 if it is advantageous to do so. System administrators might
132 choose not to use this configuration if they need to avoid mul‐
133 tiple filesystem checks running in parallel for some reason ---
134 for example, if the machine in question is short on memory so
135 that excessive paging is a concern.
136 fsck normally does not check whether the device actually exists
138 before calling a filesystem specific checker. Therefore non-
139 existing devices may cause the system to enter filesystem repair
140 mode during boot if the filesystem specific checker returns a
141 fatal error. The /etc/fstab mount option nofail may be used to
142 have fsck skip non-existing devices. fsck also skips non-exist‐
143 ing devices that have the special filesystem type auto.
144 -C [fd]
146 Display completion/progress bars for those filesystem checkers
147 (currently only for ext2 and ext3) which support them. fsck
148 will manage the filesystem checkers so that only one of them
149 will display a progress bar at a time. GUI front-ends may spec‐
150 ify a file descriptor fd, in which case the progress bar infor‐
151 mation will be sent to that file descriptor.
152 -M Do not check mounted filesystems and return an exit code of 0
154 for mounted filesystems.
155 -N Don't execute, just show what would be done.
157 -P When the -A flag is set, check the root filesystem in parallel
159 with the other filesystems. This is not the safest thing in the
160 world to do, since if the root filesystem is in doubt things
161 like the e2fsck(8) executable might be corrupted! This option
162 is mainly provided for those sysadmins who don't want to repar‐
163 tition the root filesystem to be small and compact (which is
164 really the right solution).
165 -R When checking all filesystems with the -A flag, skip the root
167 filesystem. (This is useful in case the root filesystem has
168 already been mounted read-write.)
169 -T Don't show the title on startup.
171 -V Produce verbose output, including all filesystem-specific com‐
173 mands that are executed.
174 fs-specific-options
176 Options which are not understood by fsck are passed to the
177 filesystem-specific checker. These options must not take argu‐
178 ments, as there is no way for fsck to be able to properly guess
179 which options take arguments and which don't.
180 Options and arguments which follow the -- are treated as
182 filesystem-specific options to be passed to the filesystem-spe‐
183 cific checker.
184 Please note that fsck is not designed to pass arbitrarily com‐
186 plicated options to filesystem-specific checkers. If you're
187 doing something complicated, please just execute the filesystem-
188 specific checker directly. If you pass fsck some horribly com‐
189 plicated options and arguments, and it doesn't do what you
190 expect, don't bother reporting it as a bug. You're almost cer‐
191 tainly doing something that you shouldn't be doing with fsck.
192 Options to different filesystem-specific fsck's are not standardized.
194 If in doubt, please consult the man pages of the filesystem-specific
195 checker. Although not guaranteed, the following options are supported
196 by most filesystem checkers:
197 -a Automatically repair the filesystem without any questions (use
199 this option with caution). Note that e2fsck(8) supports -a for
200 backward compatibility only. This option is mapped to e2fsck's
201 -p option which is safe to use, unlike the -a option that some
202 filesystem checkers support.
203 -n For some filesystem-specific checkers, the -n option will cause
205 the fs-specific fsck to avoid attempting to repair any problems,
206 but simply report such problems to stdout. This is however not
207 true for all filesystem-specific checkers. In particular,
208 fsck.reiserfs(8) will not report any corruption if given this
209 option. fsck.minix(8) does not support the -n option at all.
210 -r Interactively repair the filesystem (ask for confirmations).
212 Note: It is generally a bad idea to use this option if multiple
213 fsck's are being run in parallel. Also note that this is
214 e2fsck's default behavior; it supports this option for backward
215 compatibility reasons only.
216 -y For some filesystem-specific checkers, the -y option will cause
218 the fs-specific fsck to always attempt to fix any detected
219 filesystem corruption automatically. Sometimes an expert may be
220 able to do better driving the fsck manually. Note that not all
221 filesystem-specific checkers implement this option. In particu‐
222 lar fsck.minix(8) and fsck.cramfs(8) do not support the -y
223 option as of this writing.
224
226 /etc/fstab.
227
229 The fsck program's behavior is affected by the following environment
230 variables:
231 FSCK_FORCE_ALL_PARALLEL
233 If this environment variable is set, fsck will attempt to check
234 all of the specified filesystems in parallel, regardless of
235 whether the filesystems appear to be on the same device. (This
236 is useful for RAID systems or high-end storage systems such as
237 those sold by companies such as IBM or EMC.) Note that the
238 fs_passno value is still used.
239 FSCK_MAX_INST
241 This environment variable will limit the maximum number of
242 filesystem checkers that can be running at one time. This
243 allows configurations which have a large number of disks to
244 avoid fsck starting too many filesystem checkers at once, which
245 might overload CPU and memory resources available on the system.
246 If this value is zero, then an unlimited number of processes can
247 be spawned. This is currently the default, but future versions
248 of fsck may attempt to automatically determine how many filesys‐
249 tem checks can be run based on gathering accounting data from
250 the operating system.
251 PATH The PATH environment variable is used to find filesystem check‐
253 ers. A set of system directories are searched first: /sbin,
254 /sbin/fs.d, /sbin/fs, /etc/fs, and /etc. Then the set of direc‐
255 tories found in the PATH environment are searched.
256 FSTAB_FILE
258 This environment variable allows the system administrator to
259 override the standard location of the /etc/fstab file. It is
260 also useful for developers who are testing fsck.
261 LIBBLKID_DEBUG=0xffff
263 enables debug output.
264 LIBMOUNT_DEBUG=0xffff
266 enables debug output.
267
269 fstab(5), mkfs(8), fsck.ext2(8) or fsck.ext3(8) or e2fsck(8), cramf‐
270 sck(8), fsck.minix(8), fsck.msdos(8), fsck.jfs(8), fsck.nfs(8),
271 fsck.vfat(8), fsck.xfs(8), fsck.xiafs(8), reiserfsck(8).
272
274 Theodore Ts'o ⟨tytso@mit.edu⟩
275
277 The fsck command is part of the util-linux package and is available
278 from Linux Kernel Archive ⟨ftp://ftp.kernel.org/pub/linux/utils/util-
279 linux/⟩.
280util-linux February 2009 FSCK(8)