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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
2020-12-18. (At that time, the date of the most recent commit
that was found in the repository was 2020-10-01.) If you
discover any rendering problems in this HTML version of the page,
or you believe there is a better or more up-to-date source for
the page, or you have corrections or improvements to the
information in this COLOPHON (which is not part of the original
manual page), send a mail to man-pages@man7.org
E2fsprogs version 1.46-WIP March 2020 FSCK(8)
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