e2fsck - check a Linux ext2/ext3/ext4 file system
e2fsck [ -pacnyrdfkvtDFV ] [ -b
superblock ] [ -B blocksize ] [ -l|-L
bad_blocks_file ] [ -C fd ] [ -j
external-journal ] [ -E extended_options ] [ -z
undo_file ] device
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.
- -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.
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
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.
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.
This version of e2fsck was written by Theodore Ts'o
<tytso@mit.edu>.