fsck(8) — Linux manual page


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.  filesys 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

              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

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(8) 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

              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

              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.

              Display version information and exit.


       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

       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

              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.

              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

              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.

              enables libblkid debug output.

              enables libmount debug output.

FILES         top


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)

AVAILABILITY         top

       The fsck command is part of the util-linux package and is available
       from Linux Kernel Archive 

COLOPHON         top

       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
       2020-11-01.  (At that time, the date of the most recent commit that
       was found in the repository was 2020-10-21.)  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

util-linux                      February 2009                        FSCK(8)

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