1FSCK(8) MAINTENANCE COMMANDS FSCK(8)
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6 fsck - check and repair a Linux file system
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9 fsck [-sAVRTMNP] [-C [fd]] [-t fstype] [filesys...] [--] [fs-specific-
10 options]
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13 fsck is used to check and optionally repair one or more Linux file sys‐
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 the filesystems.
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
27 1 - File system errors corrected
28 2 - System should be rebooted
29 4 - File system errors left uncorrected
30 8 - Operational error
31 16 - Usage or syntax error
32 32 - Fsck canceled by user request
33 128 - Shared library error
34 The exit code returned when multiple file systems are checked is the
35 bit-wise OR of the exit codes for each file system that is checked.
36 In actuality, fsck is simply a front-end for the various file system
38 checkers (fsck.fstype) available under Linux. The file system-specific
39 checker is searched for in /sbin first, then in /etc/fs and /etc, and
40 finally in the directories listed in the PATH environment variable.
41 Please see the file system-specific checker manual pages for further
42 details.
43
45 -s Serialize fsck operations. This is a good idea if you are
46 checking multiple filesystems and the checkers are in an inter‐
47 active mode. (Note: e2fsck(8) runs in an interactive mode by
48 default. To make e2fsck(8) run in a non-interactive mode, you
49 must either specify the -p or -a option, if you wish for errors
50 to be corrected automatically, or the -n option if you do not.)
51 -t fslist
53 Specifies the type(s) of file system to be checked. When the -A
54 flag is specified, only filesystems that match fslist are
55 checked. The fslist parameter is a comma-separated list of
56 filesystems and options specifiers. All of the filesystems in
57 this comma-separated list may be prefixed by a negation operator
58 'no' or '!', which requests that only those filesystems not
59 listed in fslist will be checked. If all of the filesystems in
60 fslist are not prefixed by a negation operator, then only those
61 filesystems listed in fslist will be checked.
62 Options specifiers may be included in the comma-separated
64 fslist. They must have the format opts=fs-option. If an
65 options specifier is present, then only filesystems which con‐
66 tain fs-option in their mount options field of /etc/fstab will
67 be checked. If the options specifier is prefixed by a negation
68 operator, then only those filesystems that do not have fs-option
69 in their mount options field of /etc/fstab will be checked.
70 For example, if opts=ro appears in fslist, then only filesystems
72 listed in /etc/fstab with the ro option will be checked.
73 For compatibility with Mandrake distributions whose boot scripts
75 depend upon an unauthorized UI change to the fsck program, if a
76 filesystem type of loop is found in fslist, it is treated as if
77 opts=loop were specified as an argument to the -t option.
78 Normally, the filesystem type is deduced by searching for
80 filesys in the /etc/fstab file and using the corresponding
81 entry. If the type can not be deduced, and there is only a sin‐
82 gle filesystem given as an argument to the -t option, fsck will
83 use the specified filesystem type. If this type is not avail‐
84 able, then the default file system type (currently ext2) is
85 used.
86 -A Walk through the /etc/fstab file and try to check all file sys‐
88 tems in one run. This option is typically used from the /etc/rc
89 system initialization file, instead of multiple commands for
90 checking a single file system.
91 The root filesystem will be checked first unless the -P option
93 is specified (see below). After that, filesystems will be
94 checked in the order specified by the fs_passno (the sixth)
95 field in the /etc/fstab file. Filesystems with a fs_passno
96 value of 0 are skipped and are not checked at all. Filesystems
97 with a fs_passno value of greater than zero will be checked in
98 order, with filesystems with the lowest fs_passno number being
99 checked first. If there are multiple filesystems with the same
100 pass number, fsck will attempt to check them in parallel,
101 although it will avoid running multiple filesystem checks on the
102 same physical disk.
103 Hence, a very common configuration in /etc/fstab files is to set
105 the root filesystem to have a fs_passno value of 1 and to set
106 all other filesystems to have a fs_passno value of 2. This will
107 allow fsck to automatically run filesystem checkers in parallel
108 if it is advantageous to do so. System administrators might
109 choose not to use this configuration if they need to avoid mul‐
110 tiple filesystem checks running in parallel for some reason ---
111 for example, if the machine in question is short on memory so
112 that excessive paging is a concern.
113 fsck normally does not check whether the device actually exists
115 before calling a file system specific checker. Therefore non-
116 existing devices may cause the system to enter file system
117 repair mode during boot if the filesystem specific checker
118 returns a fatal error. The /etc/fstab mount option nofail may be
119 used to have fsck skip non-existing devices. fsck also skips
120 non-existing devices that have the special file system type auto
121 -C [ fd ]
123 Display completion/progress bars for those filesystem checkers
124 (currently only for ext2 and ext3) which support them. Fsck
125 will manage the filesystem checkers so that only one of them
126 will display a progress bar at a time. GUI front-ends may spec‐
127 ify a file descriptor fd, in which case the progress bar infor‐
128 mation will be sent to that file descriptor.
129 -M Do not check mounted filesystems and return an exit code of 0
131 for mounted filesystems.
132 -N Don't execute, just show what would be done.
134 -P When the -A flag is set, check the root filesystem in parallel
136 with the other filesystems. This is not the safest thing in the
137 world to do, since if the root filesystem is in doubt things
138 like the e2fsck(8) executable might be corrupted! This option
139 is mainly provided for those sysadmins who don't want to repar‐
140 tition the root filesystem to be small and compact (which is
141 really the right solution).
142 -R When checking all file systems with the -A flag, skip the root
144 file system (in case it's already mounted read-write).
145 -T Don't show the title on startup.
147 -V Produce verbose output, including all file system-specific com‐
149 mands that are executed.
150 fs-specific-options
152 Options which are not understood by fsck are passed to the
153 filesystem-specific checker. These arguments must not take
154 arguments, as there is no way for fsck to be able to properly
155 guess which arguments take options and which don't.
156 Options and arguments which follow the -- are treated as file
158 system-specific options to be passed to the file system-specific
159 checker.
160 Please note that fsck is not designed to pass arbitrarily com‐
162 plicated options to filesystem-specific checkers. If you're
163 doing something complicated, please just execute the filesystem-
164 specific checker directly. If you pass fsck some horribly com‐
165 plicated option and arguments, and it doesn't do what you
166 expect, don't bother reporting it as a bug. You're almost cer‐
167 tainly doing something that you shouldn't be doing with fsck.
168 Options to different filesystem-specific fsck's are not standardized.
170 If in doubt, please consult the man pages of the filesystem-specific
171 checker. Although not guaranteed, the following options are supported
172 by most file system checkers:
173 -a Automatically repair the file system without any questions (use
175 this option with caution). Note that e2fsck(8) supports -a for
176 backwards compatibility only. This option is mapped to e2fsck's
177 -p option which is safe to use, unlike the -a option that some
178 file system checkers support.
179 -n For some filesystem-specific checkers, the -n option will cause
181 the fs-specific fsck to avoid attempting to repair any problems,
182 but simply report such problems to stdout. This is however not
183 true for all filesystem-specific checkers. In particular,
184 fsck.reiserfs(8) will not report any corruption if given this
185 option. fsck.minix(8) does not support the -n option at all.
186 -r Interactively repair the filesystem (ask for confirmations).
188 Note: It is generally a bad idea to use this option if multiple
189 fsck's are being run in parallel. Also note that this is
190 e2fsck's default behavior; it supports this option for backwards
191 compatibility reasons only.
192 -y For some filesystem-specific checkers, the -y option will cause
194 the fs-specific fsck to always attempt to fix any detected
195 filesystem corruption automatically. Sometimes an expert may be
196 able to do better driving the fsck manually. Note that not all
197 filesystem-specific checkers implement this option. In particu‐
198 lar fsck.minix(8) and fsck.cramfs(8) does not support the -y
199 option as of this writing.
200
202 Theodore Ts'o (tytso@mit.edu)
203
205 The fsck command is part of the util-linux-ng package and is available
206 from ftp://ftp.kernel.org/pub/linux/utils/util-linux-ng/.
207
209 /etc/fstab.
210
212 The fsck program's behavior is affected by the following environment
213 variables:
214 FSCK_FORCE_ALL_PARALLEL
216 If this environment variable is set, fsck will attempt to run
217 all of the specified filesystems in parallel, regardless of
218 whether the filesystems appear to be on the same device. (This
219 is useful for RAID systems or high-end storage systems such as
220 those sold by companies such as IBM or EMC.)
221 FSCK_MAX_INST
223 This environment variable will limit the maximum number of file
224 system checkers that can be running at one time. This allows
225 configurations which have a large number of disks to avoid fsck
226 starting too many file system checkers at once, which might
227 overload CPU and memory resources available on the system. If
228 this value is zero, then an unlimited number of processes can be
229 spawned. This is currently the default, but future versions of
230 fsck may attempt to automatically determine how many file system
231 checks can be run based on gathering accounting data from the
232 operating system.
233 PATH The PATH environment variable is used to find file system check‐
235 ers. A set of system directories are searched first: /sbin,
236 /sbin/fs.d, /sbin/fs, /etc/fs, and /etc. Then the set of direc‐
237 tories found in the PATH environment are searched.
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
245 fstab(5), mkfs(8), fsck.ext2(8) or fsck.ext3(8) or e2fsck(8), cramf‐
246 sck(8), fsck.minix(8), fsck.msdos(8), fsck.jfs(8), fsck.nfs(8),
247 fsck.vfat(8), fsck.xfs(8), fsck.xiafs(8), reiserfsck(8).
248Linux February 2009 FSCK(8)