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Manual page and help for the fsck.ext2 linux command. E2fsck is used to check the ext2 / ext3 / ext4 file system family. For ext3 and ext4 logging file systems, if the file system was shut down incorrectly but without error, the file system can usually be marked as error-free after re-running the transactions in the log. Therefore, for file systems that use logging, e2fsck usually reruns the log and exits, unless the file system super block indicates that further verification is required.
Man page output
man fsck.ext2E2FSCK(8) System Manager's Manual 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
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 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 filesystems. The only
exception is if the -n option is specified, and -c, -l, or -L options are not speci‐
fied. 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.
If e2fsck is run in interactive mode (meaning that none of -y, -n, or -p are speci‐
fied), 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 de‐
fault response, which is printed before the question mark. Pressing Control-C termi‐
nates e2fsck immediately.
OPTIONS
-a This option does the same thing as the -p option. It is provided for back‐
wards compatibility only; it is suggested that people use -p option whenever
possible.
-b superblock
Instead of using the normal superblock, use an alternative superblock speci‐
fied by superblock. This option is normally used when the primary superblock
has been corrupted. The location of backup superblocks is dependent on the
filesystem'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 filesystem's layout
(e.g. blocksize, blocks per group, sparse_super, etc.).
If an alternative superblock is specified and the filesystem is not opened
read-only, e2fsck will make sure that the primary superblock is updated appro‐
priately 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 su‐
perblock 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 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.
-d Print debugging output (useless unless you are debugging e2fsck).
-D Optimize directories in filesystem. This option causes e2fsck to try to opti‐
mize all directories, either by reindexing them if the filesystem supports di‐
rectory indexing, or by sorting and compressing directories for smaller di‐
rectories, or for filesystems 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 in‐
dexed 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 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 filesystem. 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 fur‐
ther checks or repairs.
fragcheck
During pass 1, print a detailed report of any discontiguous blocks
for files in the filesystem.
discard
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.
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 unneces‐
sary width or depth. This can also be enabled in the options sec‐
tion 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 re‐
quired is proportional to the number of inodes in the file system.
For large file systems, this can be gigabytes of memory. (For ex‐
ample, 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
filesystem); if this amount is more than 1/50th of total physical
memory, readahead is disabled. Set this to zero to disable reada‐
head 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.
unshare_blocks
If the filesystem 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 filesystem does not have the
read-only feature bit, but has shared blocks anyway, then this op‐
tion 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 dedupli‐
cate. If this fails, the exit code will be non-zero.
-f Force checking even if the file system seems clean.
-F 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.
-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 filesystem. Hence, badblocks(8) must be given the blocksize of the
filesystem in order to obtain correct results. As a result, it is much sim‐
pler 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 be‐
fore the blocks listed in the file are added to the bad blocks list.)
-n 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 options.
-p 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 sys‐
tem 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 compatibil‐
ity.
-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-in‐
teractively. 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
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 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
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 e2fsck are in English; if your system
has been configured so that e2fsck's messages have been translated into another lan‐
guage, 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) 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 di‐
rectory, the debugfs dump command will allow you to extract the contents of the di‐
rectory 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 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)
E2fsprogs version 1.44.5 December 2018 E2FSCK(8)
Help output
sudo fsck.ext2Usage: fsck.ext2 [-panyrcdfktvDFV] [-b superblock] [-B blocksize]
[-l|-L bad_blocks_file] [-C fd] [-j external_journal]
[-E extended-options] [-z undo_file] device
Emergency help:
-p Automatic repair (no questions)
-n Make no changes to the filesystem
-y Assume "yes" to all questions
-c Check for bad blocks and add them to the badblock list
-f Force checking even if filesystem is marked clean
-v Be verbose
-b superblock Use alternative superblock
-B blocksize Force blocksize when looking for superblock
-j external_journal Set location of the external journal
-l bad_blocks_file Add to badblocks list
-L bad_blocks_file Set badblocks list
-z undo_file Create an undo file
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