Manual: fsck

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/.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 , Karel Zak 

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 .

AVAILABILITY
       The fsck command is part of the util-linux package which can be downloaded from Linux Kernel Archive
       .

util-linux 2.41.3					 2025-12-15						     FSCK(8)