E2FSCK(8)                 (August 2021)                 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 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 contain-
          ing 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
          -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 alterna-
               tive superblock specified by superblock. This option is
               normally used when the primary superblock has been cor-
               rupted.  The location of backup superblocks is

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               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 var-
               ious 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 informa-
               tion to the specified file descriptor so that the pro-
               gress 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 descrip-
               tor 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 debug-
               ging 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

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               directory indexing,  or by sorting and compressing
               directories for smaller directories, or for file sys-
               tems using traditional linear directories.

               Even without the -D option, e2fsck may sometimes opti-
               mize 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 dupli-
               cate 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 sup-
               ported:

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

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                           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 elimi-
                           nating 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 optimiza-
                           tion.  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 sys-
                           tem); if this amount is more than 1/50th of
                           total physical memory, readahead is dis-
                           abled.  Set this to zero to disable reada-
                           head entirely.

                      bmap2extent
                           Convert block-mapped files to extent-mapped

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                           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

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               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 speci-
               fied 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

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               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
          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 comple-
               tion bar or emitting progress information.  (See dis-
               cussion of the -C option.)

          SIGUSR2
               This signal causes e2fsck to stop displaying a comple-
               tion bar or emitting progress information.

     REPORTING BUGS
          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

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          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
          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)

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