e2fsck - check a Linux ext2/ext3/ext4 file system
] [ -b superblock
] [ -l
] [ -j external-journal
] [ -E
] [ -z undo_file
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
is a block device (e.g., /dev/sdc1
) or file containing the
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
, 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.
is run in interactive mode (meaning that none of -y
, 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
- 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
- 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
- -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.
- 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.
- Print debugging output (useless unless you are debugging
- 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
- 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
- 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
- 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
- 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.
- Offer to optimize the extent tree by eliminating
unnecessary width or depth. This is the default unless otherwise specified
- 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.
- Disable the inode_count_fullmap optimization. This
is the default unless otherwise specified in /etc/e2fsck.conf.
- 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
- 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 options.
- Force checking even if the file system seems clean.
- 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.
- 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.)
- 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
- 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.
- This option does nothing at all; it is provided only for
- Print timing statistics for e2fsck. If this option
is used twice, additional timing statistics are printed on a pass by pass
- Verbose mode.
- Print version information and exit.
- 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
WARNING: The undo file cannot be used to recover from a power or system
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
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
- 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
are in English; if your system has been configured so that
'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)
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
command and send the output of the stat(1u)
run on the relevant inode(s). If the inode is a directory, the debugfs
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
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