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FSCK(8)                      MAINTENANCE COMMANDS                      FSCK(8)



NAME
       fsck - check and repair a Linux file system

SYNOPSIS
       fsck [-sAVRTMNP] [-C [fd]] [-t fstype] [filesys...]  [--] [fs-specific-options]

DESCRIPTION
       fsck is used to check and optionally repair one or more Linux file systems.  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).   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 the filesystems.

       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    - File system errors corrected
            2    - System should be rebooted
            4    - File system errors left uncorrected
            8    - Operational error
            16   - Usage or syntax error
            32   - Fsck canceled by user request
            128  - Shared library error
       The exit code returned when multiple file systems are checked is the bit-wise OR of the  exit  codes  for  each
       file system that is checked.

       In  actuality,  fsck  is  simply a front-end for the various file system checkers (fsck.fstype) available under
       Linux.  The file system-specific checker is searched for in /sbin first, then in /etc/fs and /etc, and  finally
       in the directories listed in the PATH environment variable.  Please see the file system-specific checker manual
       pages for further details.

OPTIONS
       -s     Serialize fsck operations.  This is a good idea if you are checking multiple filesystems and the  check-
              ers  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  file system 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 all of the filesystems in fslist are not prefixed by a negation operator, then only those filesystems
              listed in fslist 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 can not 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 file system type (currently ext2) is used.

       -A     Walk through the /etc/fstab file and try to check all file systems in one run.  This option is typically
              used  from  the  /etc/rc  system initialization file, instead of multiple commands for checking a single
              file system.

              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 detemine 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  exces-
              sive paging is a concern.

              fsck  normally  does  not check whether the device actually exists before calling a file system specific
              checker. Therefore non-existing devices may cause the system to enter file  system  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
              file system type auto

       -C [  fd  ]
              Display  completion/progress bars for those filesystem checkers (currently only for ext2 and ext3) 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
              repartition the root filesystem to be small and compact (which is really the right solution).

       -R     When checking all file systems with the -A flag, skip the root file system (in case it's already mounted
              read-write).

       -T     Don't show the title on startup.

       -V     Produce verbose output, including all file system-specific commands that are executed.

       fs-specific-options
              Options which are not understood by fsck are passed to the filesystem-specific checker.  These arguments
              must  not  take arguments, as there is no way for fsck to be able to properly guess which arguments take
              options and which don't.

              Options and arguments which follow the -- are treated as file system-specific options to  be  passed  to
              the file system-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 option 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.  If in doubt, please consult the man
       pages of the filesystem-specific checker.  Although not guaranteed, the following options are supported by most
       file system checkers:

       -a     Automatically  repair  the  file system without any questions (use this option with caution).  Note that
              e2fsck(8) supports -a for backwards compatibility only.  This option is mapped  to  e2fsck's  -p  option
              which is safe to use, unlike the -a option that some file system checkers support.

       -n     For some filesystem-specific checkers, the -n option will cause the fs-specific fsck to avoid attempting
              to repair any problems, but simply report such problems to stdout.  This is however  not  true  for  all
              filesystem-specific  checkers.   In particular, fsck.reiserfs(8) will not report any corruption if given
              this option.  fsck.minix(8) does not support the -n option at all.

       -r     Interactively repair the filesystem (ask for confirmations).  Note: It is generally a bad  idea  to  use
              this  option  if  multiple  fsck's  are  being run in parallel.  Also note that this is e2fsck's default
              behavior; it supports this option for backwards compatibility reasons only.

       -y     For some filesystem-specific checkers, the -y option will cause the fs-specific fsck to  always  attempt
              to  fix  any detected filesystem corruption automatically.  Sometimes an expert may be able to do better
              driving the fsck manually.  Note that not all filesystem-specific checkers implement  this  option.   In
              particular fsck.minix(8) and fsck.cramfs(8) does not support the -y option as of this writing.

AUTHOR
       Theodore Ts'o (tytsoATmit.edu)

AVAILABILITY
       The   blkid   command   is   part   of   the   util-linux-ng  package  and  is  available  from  ftp://ftp.ker-
       nel.org/pub/linux/utils/util-linux-ng/.

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 run all of the specified filesystems in paral-
              lel,  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 file system checkers that can be running at
              one time.  This allows configurations which have a large number of disks to avoid fsck starting too many
              file system 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 file system checks
              can be run based on gathering accounting data from the operating system.

       PATH   The PATH environment variable is used to find file system checkers.  A set  of  system  directories  are
              searched  first:  /sbin,  /sbin/fs.d, /sbin/fs, /etc/fs, and /etc.  Then the set of directories found in
              the PATH environment are searched.

       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.

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



Linux                            February 2009                         FSCK(8)