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FSCK(8) System Administration FSCK(8)
NAME
fsck - check and repair a Linux filesystem
SYNOPSIS
fsck [-lsAVRTMNP] [-r [fd]] [-C [fd]] [-t fstype] [filesystem...] [--]
[fs-specific-options]
DESCRIPTION
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 an
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.
OPTIONS
-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.
FILESYSTEM SPECIFIC OPTIONS
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.
ENVIRONMENT
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.
FILES
/etc/fstab
AUTHORS
Theodore Ts'o <tytso AT mit.edu>>, Karel Zak <kzak AT redhat.com>
SEE ALSO
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)
REPORTING BUGS
For bug reports, use the issue tracker at https://github.com/karelzak/util-linux/issues.
AVAILABILITY
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/>.
util-linux 2.37.2 2021-07-20 FSCK(8)
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