e2fsck

E2FSCK(8)                   System Manager's Manual                  E2FSCK(8)

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

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

DESCRIPTION
       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  indi-
       cates that further checking is required.

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

       Note that in general it is not safe to run e2fsck on  mounted  filesys-
       tems.  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 sub-
       sequent   problems;  pressing  Enter  will  proceed  with  the  default
       response, which is printed before the question mark.  Pressing Control-
       C terminates e2fsck immediately.

OPTIONS
       -a     This  option  does  the same thing as the -p option.  It is pro-
              vided 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 loca-
              tion of backup superblocks  is  dependent  on  the  filesystem's
              blocksize,  the number of blocks per group, and features such as
              sparse_super.

              Additional backup superblocks can be  determined  by  using  the
              mke2fs  program  using  the  -n  option  to  print out where the
              superblocks exist, supposing mke2fs is supplied  with  arguments
              that  are  consistent  with the filesystem's layout (e.g. block-
              size, blocks per group, sparse_super, etc.).

              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 dif-
              ferent 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  particu-
              lar blocksize.  If the superblock is not found, e2fsck will ter-
              minate 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 direc-
              tory.  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 pro-
              grams 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
              e2fsck).

       -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 filesys-
              tems 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  sepa-
              rated,  and  may  take  an argument using the equals ('=') sign.
              The following options are supported:

                   ea_ver=extended_attribute_version
                          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.

                   journal_only
                          Only replay the journal if required, but do not per-
                          form any further checks or repairs.

                   fragcheck
                          During pass 1, print a detailed report of  any  dis-
                          contiguous blocks for files in the filesystem.

                   discard
                          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.

                   nodiscard
                          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.

                   no_optimize_extents
                          Do not offer to optimize the extent tree  by  elimi-
                          nating unnecessary width or depth.  This can also be
                          enabled in the options section of /etc/e2fsck.conf.

                   optimize_extents
                          Offer to optimize the  extent  tree  by  eliminating
                          unnecessary  width  or  depth.   This is the default
                          unless otherwise specified in /etc/e2fsck.conf.

                   inode_count_fullmap
                          Trade off using memory for  speed  when  checking  a
                          file  system  with  a  large  number  of hard-linked
                          files.  The amount of  memory  required  is  propor-
                          tional  to  the number of inodes in the file system.
                          For large file systems, this  can  be  gigabytes  of
                          memory.   (For  example, a 40TB file system with 2.8
                          billion inodes will consume  an  additional  5.7  GB
                          memory if this optimization is enabled.)  This opti-
                          mization can also be enabled in the options  section
                          of /etc/e2fsck.conf.

                   no_inode_count_fullmap
                          Disable  the inode_count_fullmap optimization.  This
                          is  the  default  unless  otherwise   specified   in
                          /etc/e2fsck.conf.

                   readahead_kb
                          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  filesys-
                          tem);  if  this  amount is more than 1/50th of total
                          physical memory, readahead is disabled.  Set this to
                          zero to disable readahead entirely.

                   bmap2extent
                          Convert block-mapped files to extent-mapped files.

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

       -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
              list.

       -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 filesys-
              tem 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  logi-
              cally  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 back-
              wards 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.

EXIT CODE
       The  exit  code  returned  by e2fsck is the sum of the following condi-
       tions:
            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

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

       SIGUSR1
              This signal causes e2fsck to start displaying a  completion  bar
              or  emitting  progress  information.   (See discussion of the -C
              option.)

       SIGUSR2
              This signal causes e2fsck to stop displaying a completion bar or
              emitting progress information.

REPORTING BUGS
       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  tran-
       script  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.

ENVIRONMENT
       E2FSCK_CONFIG
              Determines  the  location  of  the   configuration   file   (see
              e2fsck.conf(5)).

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

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

E2fsprogs version 1.44.1          March 2018                         E2FSCK(8)
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