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.  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
       -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
       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

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)

AVAILABILITY
       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/⟩.



util-linux                       February 2009                         FSCK(8)