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HTML rendering created 2025-02-02 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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Another version of this page is provided by the e2fsprogs project
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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | FILESYSTEM SPECIFIC OPTIONS | ENVIRONMENT | FILES | NOTES | AUTHORS | SEE ALSO | REPORTING BUGS | AVAILABILITY |
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FSCK(8) System Administration FSCK(8)
fsck - check and repair a Linux filesystem
fsck [-lsAVRTMNP] [-r [fd]] [-C [fd]] [-t fstype] [filesystem...]
[--] [fs-specific-options]
fsck is used to check and optionally repair one or more Linux
filesystems. filesystem can be a device name (e.g., /dev/hdc1,
/dev/sdb2), a mount point (e.g., /, /usr, /home), or a filesystem
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 them.
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 status returned by fsck is the sum of the following
conditions:
0
No errors
1
Filesystem errors corrected
2
System should be rebooted
4
Filesystem errors left uncorrected
8
Operational error
16
Usage or syntax error
32
Checking canceled by user request
128
Shared-library error
The exit status returned when multiple filesystems are checked is
the bit-wise OR of the exit statuses for each filesystem that is
checked.
In actuality, fsck is simply a front-end for the various
filesystem checkers (fsck.fstype) available under Linux. The
filesystem-specific checker is searched for in the PATH
environment variable. If the PATH is undefined then fallback to
/sbin.
Please see the filesystem-specific checker manual pages for
further details.
-l
Create an exclusive flock(2) lock file
(/run/fsck/<diskname>.lock) for whole-disk device. This option
can be used with one device only (this means that -A and -l
are mutually exclusive). This option is recommended when more
fsck instances are executed in the same time. The option is
ignored when used for multiple devices or for non-rotating
disks. fsck does not lock underlying devices when executed to
check stacked devices (e.g. MD or DM) - this feature is not
implemented yet.
-r [fd]
Report certain statistics for each fsck when it completes.
These statistics include the exit status, the maximum run set
size (in kilobytes), the elapsed all-clock time and the user
and system CPU time used by the fsck run. For example:
/dev/sda1: status 0, rss 92828, real 4.002804, user 2.677592,
sys 0.86186
GUI front-ends may specify a file descriptor fd, in which case
the progress bar information will be sent to that file
descriptor in a machine parsable format. For example:
/dev/sda1 0 92828 4.002804 2.677592 0.86186
-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 filesystem 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 none of
the filesystems in fslist is prefixed by a negation operator,
then only those listed filesystems 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 cannot 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 filesystem type (currently ext2)
is used.
-A
Walk through the /etc/fstab file and try to check all
filesystems in one run. This option is typically used from the
/etc/rc system initialization file, instead of multiple
commands for checking a single filesystem.
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.
fsck does not check stacked devices (RAIDs, dm-crypt, ...) in
parallel with any other device. See below for
FSCK_FORCE_ALL_PARALLEL setting. The /sys filesystem is used
to determine dependencies between devices.
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.
fsck normally does not check whether the device actually
exists before calling a filesystem specific checker. Therefore
non-existing devices may cause the system to enter filesystem
repair mode during boot if the filesystem specific checker
returns a fatal error. The /etc/fstab mount option nofail may
be used to have fsck skip non-existing devices. fsck also
skips non-existing devices that have the special filesystem
type auto.
-C [fd]
Display completion/progress bars for those filesystem checkers
(currently only for ext[234]) 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 status 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 filesystems with the -A flag, skip the root
filesystem. (This is useful in case the root filesystem has
already been mounted read-write.)
-T
Don’t show the title on startup.
-V
Produce verbose output, including all filesystem-specific
commands that are executed.
-?, --help
Display help text and exit.
--version
Display version information and exit.
Options which are not understood by fsck are passed to the
filesystem-specific checker!
These options must not take arguments, as there is no way for fsck
to be able to properly guess which options take arguments and
which don’t.
Options and arguments which follow the -- are treated as
filesystem-specific options to be passed to the
filesystem-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 options 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.
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
check 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.) Note that
the fs_passno value is still used.
FSCK_MAX_INST
This environment variable will limit the maximum number of
filesystem checkers that can be running at one time. This
allows configurations which have a large number of disks to
avoid fsck starting too many filesystem 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 filesystem checks can be run based on gathering
accounting data from the operating system.
PATH
The PATH environment variable is used to find filesystem
checkers.
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.
LIBBLKID_DEBUG=all
enables libblkid debug output.
LIBMOUNT_DEBUG=all
enables libmount debug output.
/etc/fstab
During boot, systemd does not invoke fsck -A. Instead, it
schedules the activation of mounts individually, taking into
account dependencies on backing devices, networking, and other
factors. Consequently, fsck is called individually for each
device.
Theodore Ts’o <tytso@mit.edu>, Karel Zak <kzak@redhat.com>
fstab(5), mkfs(8), fsck.ext2(8) or fsck.ext3(8) or e2fsck(8),
fsck.cramfs(8), fsck.jfs(8), fsck.nfs(8), fsck.minix(8),
fsck.msdos(8), fsck.vfat(8), fsck.xfs(8), reiserfsck(8)
For bug reports, use the issue tracker
<https://github.com/util-linux/util-linux/issues>.
The fsck command is part of the util-linux package which can be
downloaded from Linux Kernel Archive
<https://www.kernel.org/pub/linux/utils/util-linux/>. This page is
part of the util-linux (a random collection of Linux utilities)
project. Information about the project can be found at
⟨https://www.kernel.org/pub/linux/utils/util-linux/⟩. If you have a
bug report for this manual page, send it to
util-linux@vger.kernel.org. This page was obtained from the
project's upstream Git repository
⟨git://git.kernel.org/pub/scm/utils/util-linux/util-linux.git⟩ on
2025-02-02. (At that time, the date of the most recent commit that
was found in the repository was 2025-01-30.) 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
util-linux 2.41.devel-938-0a... 2025-01-15 FSCK(8)
Pages that refer to this page: systemd-dissect(1), filesystems(5), fstab(5), e2mmpstatus(8), fsadm(8), fsck.btrfs(8), fsck.minix(8), fsck.xfs(8), logsave(8), mkfs(8), mkfs.minix(8), quotacheck(8), systemd-fsck@.service(8), systemd-mountfsd.service(8), tune2fs(8)
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HTML rendering created 2025-02-02 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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