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@mit.edu>>, Karel Zak <kzak@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/util-linux/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 2.38.1 2022-05-11 FSCK(8)
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