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)