e2fsck(8) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXIT CODE | SIGNALS | REPORTING BUGS | ENVIRONMENT | AUTHOR | SEE ALSO | COLOPHON

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

NAME         top

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

SYNOPSIS         top

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

DESCRIPTION         top

       e2fsck is used to check the ext2/ext3/ext4 family of file
       systems.  For ext3 and ext4 file systems 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
       file systems that use journaling, 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 system.

       Note that in general it is not safe to run e2fsck on mounted file
       systems.  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 file system is mounted.   If e2fsck asks whether or not
       you should check a file system 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 file system.  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.

OPTIONS         top

       -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 backup superblocks is
              dependent on the file system'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 file system's
              layout (e.g. blocksize, blocks per group, sparse_super,
              etc.).

              If an alternative superblock is specified and the file
              system is not opened read-only, e2fsck will make sure that
              the primary superblock is updated appropriately upon
              completion of the file system 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 file system 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 file system.  This option causes
              e2fsck to try to optimize all directories, either by re-
              indexing them if the file system supports directory
              indexing,  or by sorting and compressing directories for
              smaller directories, or for file systems 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 file system 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:

                   ea_ver=extended_attribute_version
                          Set the version of the extended attribute
                          blocks which e2fsck will require while
                          checking the file system.  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 file
                          system.

                   discard
                          Attempt to discard free blocks and unused
                          inode blocks after the full file system check
                          (discarding blocks is useful on solid state
                          devices and sparse / thin-provisioned
                          storage). Note that discard is done in pass 5
                          AFTER the file system 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
                          eliminating 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 proportional 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 optimization
                          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 file system); 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.

                   check_encoding
                          Force verification of encoded filenames in
                          case-insensitive directories.  This is the
                          default mode if the file system has the strict
                          flag enabled.

                   unshare_blocks
                          If the file system has shared blocks, with the
                          shared blocks read-only feature enabled, then
                          this will unshare all shared blocks and unset
                          the read-only feature bit. If there is not
                          enough free space then the operation will
                          fail.  If the file system does not have the
                          read-only feature bit, but has shared blocks
                          anyway, then this option will have no effect.
                          Note when using this option, if there is no
                          free space to clone blocks, there is no prompt
                          to delete files and instead the operation will
                          fail.

                          Note that unshare_blocks implies the "-f"
                          option to ensure that all passes are run.
                          Additionally, if "-n" is also specified,
                          e2fsck will simulate trying to allocate enough
                          space to deduplicate. If this fails, the exit
                          code will be non-zero.

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

       -F     Flush the file system 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 file
              system 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 file system.  Hence, badblocks(8) must be
              given the blocksize of the file system 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 file system 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 file
              system 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.

EXIT CODE         top

       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         top

       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         top

       Almost any piece of software will have bugs.  If you manage to
       find a file system 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 file system
       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
       file system, 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         top

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

AUTHOR         top

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

SEE ALSO         top

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

COLOPHON         top

       This page is part of the e2fsprogs (utilities for ext2/3/4
       filesystems) project.  Information about the project can be found
       at ⟨http://e2fsprogs.sourceforge.net/⟩.  It is not known how to
       report bugs for this man page; if you know, please send a mail to
       man-pages@man7.org.  This page was obtained from the project's
       upstream Git repository
       ⟨git://git.kernel.org/pub/scm/fs/ext2/e2fsprogs.git⟩ on
       2021-08-27.  (At that time, the date of the most recent commit
       that was found in the repository was 2021-08-22.)  If you
       discover any rendering problems in this HTML version of the page,
       or you believe there is a better or more up-to-date source for
       the page, or you have corrections or improvements to the
       information in this COLOPHON (which is not part of the original
       manual page), send a mail to man-pages@man7.org

E2fsprogs version 1.46.4       August 2021                     E2FSCK(8)

Pages that refer to this page: fuse2fs(1)lseek64(3)e2fsck.conf(5)ext4(5)mke2fs.conf(5)badblocks(8)debugfs(8)dumpe2fs(8)e2freefrag(8)e2image(8)e2mmpstatus(8)fsck(8@@e2fsprogs)fsck(8)mke2fs(8)mklost+found(8)quotacheck(8)resize2fs(8)tune2fs(8)