FSCK linux command manual

FSCK(8)                                                                FSCK(8)

       fsck - check and repair a Linux file system

       fsck  [  -sACVRTNP  ] [ -t fstype ] [filesys ... ] [--] [ fs-specific-
       options ]

       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).  Nor-
       mally, the fsck program will try to run filesystems on different phys-
       ical  disk drives in parallel to reduce total amount time 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 serial.  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-spe-
       cific 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.

       -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 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 opera-
              tor '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 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

              For example, if opts=ro appears in fslist, then  only  filesys-
              tems 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  pro-
              gram,  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

              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 sys-
              tems in one run.   This  option  is  typically  used  from  the
              /etc/rc system initalization 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.

              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 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.

       -C     Display completion/progress bars for those filesystems checkers
              (currently  only for ext2) which support them.   Fsck will man-
              age the filesystem checkers so that only one of them will  dis-
              play a progress bar at a time.

       -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 com-
              mands that are executed.

              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-spe-
              cific checker.

              Please note that fsck is not designed to pass arbitrarily  com-
              plicated  options  to  filesystem-specific checkers.  If you're
              doing something complicated, please just execute  the  filesys-
              tem-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 cer-
              tainly 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  prob-
              lems,  but simply report such problems to stdout.  This is how-
              ever not true for all filesystem-specific checkers.  In partic-
              ular,  fsck.reiserfs(8) will not report any corruption if given
              this option.  fsck.minix(8) does not support the -n  option  at

       -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  back-
              wards 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.

       Theodore Ts'o (tytso@mit.edu)


       The  fsck  program's behavior is affected by the following environment

              If this environment variable is set, fsck will attempt  to  run
              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.)

              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.

              This environment variable allows the  system  administrator  to
              override  the  standard location of the /etc/fstab file.  It is
              also use for developers who are testing fsck.

       fstab(5),   mkfs(8),   fsck.ext2(8)    or    e2fsck(8),    cramfsck(8)
       fsck.minix(8), fsck.jfs(8) fsck.xfs(8), fsck.xiafs(8) reiserfsck(8).

E2fsprogs version 1.35          February 2004                         FSCK(8)