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  filesys-
       tems.   filesys  can  be  a device name (e.g.  /dev/hdc1, /dev/sdb2), a
       mount point (e.g.  /, /usr, /home), or an ext2 label or UUID  specifier
       (e.g.   UUID=8868abf6-88c5-4a83-98b8-bfc24057f7bd or LABEL=root).  Nor-
       mally, 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 code 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 code returned when multiple filesystems  are  checked  is  the
       bit-wise OR of the exit codes 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  descrip-
              tor 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  inter-
              active  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  con-
              tain  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  sin-
              gle  filesystem given as an argument to the -t option, fsck will
              use the specified filesystem type.  If this type is  not  avail-
              able, then the default filesystem type (currently ext2) is used.

       -A     Walk  through  the /etc/fstab file and try to check all filesys-
              tems 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  mul-
              tiple  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-exist-
              ing 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  code  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 repar-
              tition 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 com-
              mands 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 argu-
       ments,  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.

FILES
       /etc/fstab

ENVIRONMENT VARIABLES
       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 filesys-
              tem checks can be run based on gathering  accounting  data  from
              the operating system.

       PATH   The  PATH environment variable is used to find filesystem check-
              ers.

       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.

SEE ALSO
       fstab(5), mkfs(8), fsck.ext2(8) or fsck.ext3(8) or e2fsck(8), cramf-
       sck(8), fsck.jfs(8), fsck.nfs(8), fsck.minix(8), fsck.msdos(8),
       fsck.vfat(8), fsck.xfs(8), reiserfsck(8)

AUTHORS
       Theodore Ts'o <tytso@mit.edu>
       Karel Zak <kzak@redhat.com>

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)
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