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 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/>.