e2fsck - check a Linux ext2/ext3/ext4 file system


   e2fsck  [  -pacnyrdfkvtDFV ] [ -b superblock ] [ -B blocksize ] [ -l|-L
   bad_blocks_file  ]  [  -C  fd  ]  [  -j   external-journal   ]   [   -E
   extended_options ] [ -z undo_file ] device


   e2fsck is used to check the ext2/ext3/ext4 family of file systems.  For
   ext3 and ext4 filesystems that use a journal, if the  system  has  been
   shut  down  uncleanly without any errors, normally, after replaying the
   committed transactions  in the  journal,  the  file  system  should  be
   marked  as clean.   Hence, for filesystems that use journalling, e2fsck
   will normally replay  the  journal  and  exit,  unless  its  superblock
   indicates that further checking is required.

   device  is a block device (e.g., /dev/sdc1) or file containing the file

   Note that  in  general  it  is  not  safe  to  run  e2fsck  on  mounted
   filesystems.   The only exception is if the -n option is specified, and
   -c, -l, or -L options are not specified.   However, even if it is  safe
   to do so, the results printed by e2fsck are not valid if the filesystem
   is mounted.   If  e2fsck  asks  whether  or  not  you  should  check  a
   filesystem  which  is mounted, the only correct answer is ``no''.  Only
   experts who really know what they are doing should  consider  answering
   this question in any other way.

   If  e2fsck  is run in interactive mode (meaning that none of -y, -n, or
   -p are specified), the program will ask the user to  fix  each  problem
   found  in  the  filesystem.   A response of 'y' will fix the error; 'n'
   will leave the error unfixed; and 'a' will  fix  the  problem  and  all
   subsequent  problems;  pressing  Enter  will  proceed  with the default
   response, which is printed before the question mark.  Pressing Control-
   C terminates e2fsck immediately.


   -a     This  option  does  the  same  thing  as  the  -p option.  It is
          provided for backwards compatibility only; it is suggested  that
          people use -p option whenever possible.

   -b superblock
          Instead  of  using  the  normal  superblock,  use an alternative
          superblock specified by superblock.   This  option  is  normally
          used  when  the  primary  superblock  has  been  corrupted.  The
          location  of  the  backup  superblock  is   dependent   on   the
          filesystem's  blocksize.   For filesystems with 1k blocksizes, a
          backup superblock can be found at block  8193;  for  filesystems
          with  2k  blocksizes,  at block 16384; and for 4k blocksizes, at
          block 32768.

          Additional backup superblocks can be  determined  by  using  the
          mke2fs  program  using  the  -n  option  to  print out where the
          superblocks were created.    The  -b  option  to  mke2fs,  which
          specifies blocksize of the filesystem must be specified in order
          for  the  superblock  locations  that  are  printed  out  to  be

          If  an alternative superblock is specified and the filesystem is
          not opened read-only, e2fsck will make  sure  that  the  primary
          superblock  is  updated  appropriately  upon  completion  of the
          filesystem check.

   -B blocksize
          Normally, e2fsck will  search  for  the  superblock  at  various
          different  block  sizes  in  an  attempt to find the appropriate
          block size.  This search can be  fooled  in  some  cases.   This
          option  forces  e2fsck  to only try locating the superblock at a
          particular blocksize.  If the superblock is  not  found,  e2fsck
          will terminate with a fatal error.

   -c     This  option  causes  e2fsck to use badblocks(8) program to do a
          read-only scan of the device in order to find  any  bad  blocks.
          If  any  bad  blocks  are found, they are added to the bad block
          inode to  prevent  them  from  being  allocated  to  a  file  or
          directory.   If  this  option  is  specified twice, then the bad
          block scan will be done using a non-destructive read-write test.

   -C fd  This option causes e2fsck to write completion information to the
          specified file descriptor so that the progress of the filesystem
          check can be  monitored.   This  option  is  typically  used  by
          programs  which  are  running  e2fsck.   If  the file descriptor
          number is negative, then absolute value of the  file  descriptor
          will  be  used,  and the progress information will be suppressed
          initially.  It can  later  be  enabled  by  sending  the  e2fsck
          process  a  SIGUSR1 signal.  If the file descriptor specified is
          0, e2fsck will print a completion  bar  as  it  goes  about  its
          business.   This  requires  that  e2fsck  is  running on a video
          console or terminal.

   -d     Print  debugging  output  (useless  unless  you  are   debugging

   -D     Optimize  directories  in filesystem.  This option causes e2fsck
          to try to optimize all directories, either by reindexing them if
          the  filesystem  supports directory indexing,  or by sorting and
          compressing  directories  for  smaller   directories,   or   for
          filesystems using traditional linear directories.

          Even  without the -D option, e2fsck may sometimes optimize a few
          directories --- for example, if directory  indexing  is  enabled
          and  a  directory  is  not  indexed and would benefit from being
          indexed, or if the index structures are corrupted and need to be
          rebuilt.  The -D option forces all directories in the filesystem
          to be optimized.  This can sometimes make them a little  smaller
          and  slightly  faster  to  search,  but  in practice, you should
          rarely need to use this option.

          The -D option will detect directory entries with duplicate names
          in  a  single  directory, which e2fsck normally does not enforce
          for performance reasons.

   -E extended_options
          Set  e2fsck  extended  options.   Extended  options  are   comma
          separated, and may take an argument using the equals ('=') sign.
          The following options are supported:

                      Set the version of  the  extended  attribute  blocks
                      which   e2fsck   will  require  while  checking  the
                      filesystem.  The version number may be 1 or 2.   The
                      default extended attribute version format is 2.

                      Only  replay  the  journal  if  required, but do not
                      perform any further checks or repairs.

                      During pass  1,  print  a  detailed  report  of  any
                      discontiguous blocks for files in the filesystem.

                      Attempt  to  discard  free  blocks  and unused inode
                      blocks after the full filesystem  check  (discarding
                      blocks is useful on solid state devices and sparse /
                      thin-provisioned storage). Note that discard is done
                      in  pass  5  AFTER  the  filesystem  has  been fully
                      checked and only if it does not contain recognizable
                      errors.  However  there  might be cases where e2fsck
                      does not fully recognize a problem and hence in this
                      case this option may prevent you from further manual
                      data recovery.

                      Do not attempt to discard  free  blocks  and  unused
                      inode blocks. This option is exactly the opposite of
                      discard option. This is set as default.

                      Use this many KiB of memory to pre-fetch metadata in
                      the  hopes  of reducing e2fsck runtime.  By default,
                      this is set to the size of two block  groups'  inode
                      tables   (typically   4MiB   on   a   regular   ext4
                      filesystem); if this amount is more than  1/50th  of
                      total  physical  memory, readahead is disabled.  Set
                      this to zero to disable readahead entirely.

                      Convert block-mapped files to extent-mapped files.

                      Only fix damaged metadata;  do  not  optimize  htree
                      directories  or  compress extent trees.  This option
                      is incompatible  with  the  -D  and  -E  bmap2extent

   -f     Force checking even if the file system seems clean.

   -F     Flush  the  filesystem  device's buffer caches before beginning.
          Only really useful for doing e2fsck time trials.

   -j external-journal
          Set the pathname where the external-journal for this  filesystem
          can be found.

   -k     When combined with the -c option, any existing bad blocks in the
          bad blocks list are preserved, and any new bad blocks  found  by
          running  badblocks(8)  will  be added to the existing bad blocks

   -l filename
          Add the block numbers listed in the file specified  by  filename
          to  the list of bad blocks.  The format of this file is the same
          as the one generated by the badblocks(8) program.  Note that the
          block  numbers  are  based  on  the blocksize of the filesystem.
          Hence,  badblocks(8)  must  be  given  the  blocksize   of   the
          filesystem  in order to obtain correct results.  As a result, it
          is much simpler and safer to use the -c option to e2fsck,  since
          it  will  assure  that  the correct parameters are passed to the
          badblocks program.

   -L filename
          Set the bad blocks list to be the list of  blocks  specified  by
          filename.  (This option is the same as the -l option, except the
          bad blocks list is cleared before the blocks listed in the  file
          are added to the bad blocks list.)

   -n     Open  the  filesystem read-only, and assume an answer of `no' to
          all questions.  Allows  e2fsck  to  be  used  non-interactively.
          This  option  may not be specified at the same time as the -p or
          -y options.

   -p     Automatically repair ("preen") the  file  system.   This  option
          will  cause  e2fsck to automatically fix any filesystem problems
          that can be safely fixed without human intervention.  If  e2fsck
          discovers  a  problem which may require the system administrator
          to take  additional  corrective  action,  e2fsck  will  print  a
          description  of  the  problem  and  then  exit  with the value 4
          logically  or'ed  into  the  exit  code.   (See  the  EXIT  CODE
          section.)   This  option  is  normally used by the system's boot
          scripts.  It may not be specified at the same time as the -n  or
          -y options.

   -r     This  option  does  nothing  at  all;  it  is  provided only for
          backwards compatibility.

   -t     Print timing statistics for e2fsck.   If  this  option  is  used
          twice,  additional  timing  statistics  are printed on a pass by
          pass basis.

   -v     Verbose mode.

   -V     Print version information and exit.

   -y     Assume an answer of `yes' to all questions; allows e2fsck to  be
          used non-interactively.  This option may not be specified at the
          same time as the -n or -p options.

   -z undo_file
          Before overwriting a file system block, write the  old  contents
          of  the  block to an undo file.  This undo file can be used with
          e2undo(8) to restore the old contents of the file system  should
          something  go  wrong.   If  the  empty  string  is passed as the
          undo_file argument, the undo file will  be  written  to  a  file
          named  e2fsck-device.e2undo  in  the directory specified via the
          E2FSPROGS_UNDO_DIR environment variable.

          WARNING: The undo file cannot be used to recover from a power or
          system crash.


   The  exit  code  returned  by  e2fsck  is  the  sum  of  the  following
        0    - No errors
        1    - File system errors corrected
        2    - File system errors corrected, system should
               be rebooted
        4    - File system errors left uncorrected
        8    - Operational error
        16   - Usage or syntax error
        32   - E2fsck canceled by user request
        128  - Shared library error


   The following signals have the following effect when sent to e2fsck.

          This signal causes e2fsck to start displaying a  completion  bar
          or  emitting  progress  information.   (See discussion of the -C

          This signal causes e2fsck to stop displaying a completion bar or
          emitting progress information.


   Almost  any  piece of software will have bugs.  If you manage to find a
   filesystem which causes e2fsck to crash, or which e2fsck is  unable  to
   repair, please report it to the author.

   Please  include  as  much  information  as possible in your bug report.
   Ideally, include a complete transcript of the e2fsck run, so I can  see
   exactly  what  error  messages  are displayed.  (Make sure the messages
   printed by e2fsck are in English; if your system has been configured so
   that  e2fsck's  messages  have  been  translated into another language,
   please set the the  LC_ALL  environment  variable  to  C  so  that  the
   transcript  of  e2fsck's  output  will be useful to me.)  If you have a
   writable filesystem where the transcript can be stored,  the  script(1)
   program is a handy way to save the output of e2fsck to a file.

   It  is  also  useful  to send the output of dumpe2fs(8).  If a specific
   inode or inodes seems to be giving  e2fsck  trouble,  try  running  the
   debugfs(8)  command  and send the output of the stat(1u) command run on
   the relevant inode(s).  If the inode is a directory, the  debugfs  dump
   command  will allow you to extract the contents of the directory inode,
   which can sent to me after being first run  through  uuencode(1).   The
   most useful data you can send to help reproduce the bug is a compressed
   raw image dump of the filesystem, generated using e2image(8).  See  the
   e2image(8) man page for more details.

   Always include the full version string which e2fsck displays when it is
   run, so I know which version you are running.


   This version of e2fsck was written by Theodore Ts'o <tytso@mit.edu>.


   e2fsck.conf(5),  badblocks(8),  dumpe2fs(8),  debugfs(8),   e2image(8),
   mke2fs(8), tune2fs(8)


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