fsck(8) — Linux manual page

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

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
       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(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 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)

AVAILABILITY         top

       The fsck command is part of the util-linux package and is
       available from Linux Kernel Archive 
       ⟨https://www.kernel.org/pub/linux/utils/util-linux/⟩.

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
       2020-12-18.  (At that time, the date of the most recent commit
       that was found in the repository was 2020-12-17.)  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                    February 2009                      FSCK(8)

Pages that refer to this page: systemd-dissect(1)filesystems(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@.service(8)tune2fs(8)