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FSCK(8) System Manager's Manual FSCK(8)
fsck - check and repair a Linux file system
fsck [ -sAVRTMNP ] [ -C [ fd ] ] [ -t fstype ] [filesys ... ] [--] [
fs-specific-options ]
fsck is used to check and optionally repair one or more Linux file
systems. filesys can be a device name (e.g. /dev/hdc1, /dev/sdb2),
a mount point (e.g. /, /usr, /home), or an ext2 label or UUID
specifier (e.g. UUID=8868abf6-88c5-4a83-98b8-bfc24057f7bd or
LABEL=root). Normally, the fsck program will try to handle
filesystems on different physical disk drives in parallel to reduce
the total amount of time needed to check all of the filesystems.
If no filesystems are specified on the command line, and the -A
option is not specified, fsck will default to checking filesystems in
/etc/fstab serially. This is equivalent to the -As options.
The exit code returned by fsck is the sum of the following
conditions:
0 - No errors
1 - File system errors corrected
2 - System should be rebooted
4 - File system errors left uncorrected
8 - Operational error
16 - Usage or syntax error
32 - Fsck canceled by user request
128 - Shared library error
The exit code returned when multiple file systems are checked is the
bit-wise OR of the exit codes for each file system that is checked.
In actuality, fsck is simply a front-end for the various file system
checkers (fsck.fstype) available under Linux. The file system-
specific checker is searched for in /sbin first, then in /etc/fs and
/etc, and finally in the directories listed in the PATH environment
variable. Please see the file system-specific checker manual pages
for further details.
-s Serialize fsck operations. This is a good idea if you are
checking multiple filesystems and the checkers are in an
interactive mode. (Note: e2fsck(8) runs in an interactive
mode by default. To make e2fsck(8) run in a non-interactive
mode, you must either specify the -p or -a option, if you wish
for errors to be corrected automatically, or the -n option if
you do not.)
-t fslist
Specifies the type(s) of file system to be checked. When the
-A flag is specified, only filesystems that match fslist are
checked. The fslist parameter is a comma-separated list of
filesystems and options specifiers. All of the filesystems in
this comma-separated list may be prefixed by a negation
operator 'no' or '!', which requests that only those
filesystems not listed in fslist will be checked. If all of
the filesystems in fslist are not prefixed by a negation
operator, then only those filesystems listed in fslist will be
checked.
Options specifiers may be included in the comma-separated
fslist. They must have the format opts=fs-option. If an
options specifier is present, then only filesystems which
contain fs-option in their mount options field of /etc/fstab
will be checked. If the options specifier is prefixed by a
negation operator, then only those filesystems that do not
have fs-option in their mount options field of /etc/fstab will
be checked.
For example, if opts=ro appears in fslist, then only
filesystems listed in /etc/fstab with the ro option will be
checked.
For compatibility with Mandrake distributions whose boot
scripts depend upon an unauthorized UI change to the fsck
program, if a filesystem type of loop is found in fslist, it
is treated as if opts=loop were specified as an argument to
the -t option.
Normally, the filesystem type is deduced by searching for
filesys in the /etc/fstab file and using the corresponding
entry. If the type can not be deduced, and there is only a
single filesystem given as an argument to the -t option, fsck
will use the specified filesystem type. If this type is not
available, then the default file system type (currently ext2)
is used.
-A Walk through the /etc/fstab file and try to check all file
systems in one run. This option is typically used from the
/etc/rc system initialization file, instead of multiple
commands for checking a single file system.
The root filesystem will be checked first unless the -P option
is specified (see below). After that, filesystems will be
checked in the order specified by the fs_passno (the sixth)
field in the /etc/fstab file. Filesystems with a fs_passno
value of 0 are skipped and are not checked at all.
Filesystems with a fs_passno value of greater than zero will
be checked in order, with filesystems with the lowest
fs_passno number being checked first. If there are multiple
filesystems with the same pass number, fsck will attempt to
check them in parallel, although it will avoid running
multiple filesystem checks on the same physical disk.
Hence, a very common configuration in /etc/fstab files is to
set the root filesystem to have a fs_passno value of 1 and to
set all other filesystems to have a fs_passno value of 2.
This will allow fsck to automatically run filesystem checkers
in parallel if it is advantageous to do so. System
administrators might choose not to use this configuration if
they need to avoid multiple filesystem checks running in
parallel for some reason --- for example, if the machine in
question is short on memory so that excessive paging is a
concern.
-C [ fd ]
Display completion/progress bars for those filesystem checkers
(currently only for ext2 and ext3) which support them. Fsck
will manage the filesystem checkers so that only one of them
will display a progress bar at a time. GUI front-ends may
specify a file descriptor fd, in which case the progress bar
information will be sent to that file descriptor.
-M Do not check mounted filesystems and return an exit code of 0
for mounted filesystems.
-N Don't execute, just show what would be done.
-P When the -A flag is set, check the root filesystem in parallel
with the other filesystems. This is not the safest thing in
the world to do, since if the root filesystem is in doubt
things like the e2fsck(8) executable might be corrupted! This
option is mainly provided for those sysadmins who don't want
to repartition the root filesystem to be small and compact
(which is really the right solution).
-R When checking all file systems with the -A flag, skip the root
file system (in case it's already mounted read-write).
-T Don't show the title on startup.
-V Produce verbose output, including all file system-specific
commands that are executed.
fs-specific-options
Options which are not understood by fsck are passed to the
filesystem-specific checker. These arguments must not take
arguments, as there is no way for fsck to be able to properly
guess which arguments take options and which don't.
Options and arguments which follow the -- are treated as file
system-specific options to be passed to the file system-
specific checker.
Please note that fsck is not designed to pass arbitrarily
complicated options to filesystem-specific checkers. If
you're doing something complicated, please just execute the
filesystem-specific checker directly. If you pass fsck some
horribly complicated option and arguments, and it doesn't do
what you expect, don't bother reporting it as a bug. You're
almost certainly doing something that you shouldn't be doing
with fsck.
Options to different filesystem-specific fsck's are not standardized.
If in doubt, please consult the man pages of the filesystem-specific
checker. Although not guaranteed, the following options are
supported by most file system checkers:
-a Automatically repair the file system without any questions
(use this option with caution). Note that e2fsck(8) supports
-a for backwards compatibility only. This option is mapped to
e2fsck's -p option which is safe to use, unlike the -a option
that some file system checkers support.
-n For some filesystem-specific checkers, the -n option will
cause the fs-specific fsck to avoid attempting to repair any
problems, but simply report such problems to stdout. This is
however not true for all filesystem-specific checkers. In
particular, fsck.reiserfs(8) will not report any corruption if
given this option. fsck.minix(8) does not support the -n
option at all.
-r Interactively repair the filesystem (ask for confirmations).
Note: It is generally a bad idea to use this option if
multiple fsck's are being run in parallel. Also note that
this is e2fsck's default behavior; it supports this option for
backwards compatibility reasons only.
-y For some filesystem-specific checkers, the -y option will
cause the fs-specific fsck to always attempt to fix any
detected filesystem corruption automatically. Sometimes an
expert may be able to do better driving the fsck manually.
Note that not all filesystem-specific checkers implement this
option. In particular fsck.minix(8) and fsck.cramfs(8) does
not support the -y option as of this writing.
Theodore Ts'o (tytso@mit.edu)
/etc/fstab.
The fsck program's behavior is affected by the following environment
variables:
FSCK_FORCE_ALL_PARALLEL
If this environment variable is set, fsck will attempt to run
all of the specified filesystems in parallel, regardless of
whether the filesystems appear to be on the same device.
(This is useful for RAID systems or high-end storage systems
such as those sold by companies such as IBM or EMC.)
FSCK_MAX_INST
This environment variable will limit the maximum number of
file system checkers that can be running at one time. This
allows configurations which have a large number of disks to
avoid fsck starting too many file system checkers at once,
which might overload CPU and memory resources available on the
system. If this value is zero, then an unlimited number of
processes can be spawned. This is currently the default, but
future versions of fsck may attempt to automatically determine
how many file system checks can be run based on gathering
accounting data from the operating system.
PATH The PATH environment variable is used to find file system
checkers. A set of system directories are searched first:
/sbin, /sbin/fs.d, /sbin/fs, /etc/fs, and /etc. Then the set
of directories found in the PATH environment are searched.
FSTAB_FILE
This environment variable allows the system administrator to
override the standard location of the /etc/fstab file. It is
also useful for developers who are testing fsck.
fstab(5), mkfs(8), fsck.ext2(8) or fsck.ext3(8) or e2fsck(8),
cramfsck(8), fsck.minix(8), fsck.msdos(8), fsck.jfs(8), fsck.nfs(8),
fsck.vfat(8), fsck.xfs(8), fsck.xiafs(8), reiserfsck(8).
This page is part of the e2fsprogs (utilities for ext2/3/4
filesystems) project. Information about the project can be found at
⟨http://e2fsprogs.sourceforge.net/⟩. It is not known how to report
bugs for this man page; if you know, please send a mail to
man-pages@man7.org. This page was obtained from the project's
upstream Git repository
⟨git://git.kernel.org/pub/scm/fs/ext2/e2fsprogs.git⟩ on 2017-07-05.
If you discover any rendering problems in this HTML version of the
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send a mail to man-pages@man7.org
E2fsprogs version 1.43.5-WIP February 2017 FSCK(8)