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 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
- 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
- -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
- 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 linear
- 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
- -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
- 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.
- Only replay the journal if required, but do not perform any further checks
- 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 as default.
- 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 entirely.
- 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
- 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
- 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 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 backwards
- Print timing statistics for e2fsck. If this option is used twice,
additional timing statistics are printed on a pass by pass basis.
- 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 variable.
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 -C
- 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
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