fsck.ext4dev <root
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 ] 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  indicates  that  further
       checking is required.

       device is the device file where the filesystem is stored (e.g.  /dev/hdc1).

       Note that in general it is not safe to run e2fsck on mounted filesystems.  The only excep‐
       tion is if the -n option is specified, and -c, -l, or -L options are not specified.   How‐
       ever,  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.

OPTIONS
       -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 cor‐
              rupted.   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 block‐
              sizes, 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 accurate.

              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 particu‐
              lar 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 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 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 direc‐
              tory, 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:

                   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  perform  any  further
                          checks or repairs.

                   fragcheck
                          During  pass 1, print a detailed report of any discontiguous 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.

       -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  bad‐
              blocks(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 adminis‐
              trator 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 tim‐
              ing 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-interac‐
              tively.  This option may not be specified at the same time as the -n or -p options.

EXIT CODE
       The exit code returned by e2fsck is the sum of the following conditions:
            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  dis‐
       played.  (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.

AUTHOR
       This version of e2fsck was written by Theodore Ts'o .

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

E2fsprogs version 1.42.13                    May 2015                                   E2FSCK(8)

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