fsck - check and repair a Linux filesystem


   fsck  [-lsAVRTMNP] [-r [fd]] [-C [fd]] [-t fstype] [filesystem...] [--]


   fsck is  used  to  check  and  optionally  repair  one  or  more  Linux
   filesystems.    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 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


   -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
          descriptor 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
          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

   -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
          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

          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 filesystem type (currently ext2) is

   -A     Walk  through  the  /etc/fstab  file  and  try  to   check   all
          filesystems  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
          multiple 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-
          existing 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
          repartition  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
          commands that are executed.


   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
   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.




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

          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.

          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
          filesystem  checks can be run based on gathering accounting data
          from the operating system.

   PATH   The  PATH  environment  variable  is  used  to  find  filesystem

          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.

          enables libblkid debug output.

          enables libmount debug output.


   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), reiserfsck(8).


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


   The  fsck  command  is  part of the util-linux package and is available
   from Linux Kernel  Archive  ftp://ftp.kernel.org/pub/linux/utils/util-

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