fsck(8) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | OPTIONS | FILESYSTEM SPECIFIC OPTIONS | ENVIRONMENT | FILES | AUTHORS | SEE ALSO | REPORTING BUGS | AVAILABILITY

FSCK(8)                   System Administration                  FSCK(8)

NAME         top

       fsck - check and repair a Linux filesystem

SYNOPSIS         top

       fsck [-lsAVRTMNP] [-r [fd]] [-C [fd]] [-t fstype] [filesystem...]
       [--] [fs-specific-options]

DESCRIPTION         top

       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         top

       -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         top

       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         top

       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         top

       /etc/fstab

AUTHORS         top

       Theodore Ts’o <tytso@mit.edu>>, Karel Zak <kzak@redhat.com>

SEE ALSO         top

       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         top

       For bug reports, use the issue tracker at
       https://github.com/karelzak/util-linux/issues.

AVAILABILITY         top

       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/>. This page
       is part of the util-linux (a random collection of Linux
       utilities) project. Information about the project can be found at
       ⟨https://www.kernel.org/pub/linux/utils/util-linux/⟩. If you have
       a bug report for this manual page, send it to
       util-linux@vger.kernel.org. This page was obtained from the
       project's upstream Git repository
       ⟨git://git.kernel.org/pub/scm/utils/util-linux/util-linux.git⟩ on
       2021-08-27. (At that time, the date of the most recent commit
       that was found in the repository was 2021-08-24.) If you discover
       any rendering problems in this HTML version of the page, or you
       believe there is a better or more up-to-date source for the page,
       or you have corrections or improvements to the information in
       this COLOPHON (which is not part of the original manual page),
       send a mail to man-pages@man7.org

util-linux 2.37.109-b366e69    2021-06-20                        FSCK(8)

Pages that refer to this page: systemd-dissect(1)filesystems(5)fstab(5)e2mmpstatus(8)fsadm(8)fsck.btrfs(8)fsck.minix(8)fsck.xfs(8)logsave(8)mkfs(8)mkfs.minix(8)quotacheck(8)systemd-fsck@.service(8)tune2fs(8)