fsck


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 sys-
       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 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 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 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

              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 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 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  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.

              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  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 spec-
              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 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.

       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 com-
              plicated 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  com-
              plicated  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 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.

       The blkid command is part of the util-linux-ng package and is available
       from ftp://ftp.kernel.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  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.)

       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 check-
              ers.   A  set  of  system directories are searched first: /sbin,
              /sbin/fs.d, /sbin/fs, /etc/fs, and /etc.  Then the set of direc-
              tories 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), cramf-
       sck(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)
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