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    Command:

    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
                  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.
    
                  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 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
    
           -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 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.
    
    
    

    AUTHOR

           Theodore Ts'o (tytso@mit.edu)
    
    
    

    AVAILABILITY

           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.)  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 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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