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 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.

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

NOTES
       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.

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
       <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 2.41.2		  2025-09-22			       FSCK(8)