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HTML rendering created 2024-06-26 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 <[email protected]>>, Karel Zak <[email protected]>
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 at
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
[email protected]. This page was obtained from the
project's upstream Git repository
⟨git://git.kernel.org/pub/scm/utils/util-linux/util-linux.git⟩ on
2024-06-14. (At that time, the date of the most recent commit
that was found in the repository was 2024-06-10.) 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 [email protected]
util-linux 2.41.devel-537-e... 2024-06-13 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), [email protected](8), tune2fs(8)
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HTML rendering created 2024-06-26 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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