E2FSCK(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 exter‐
nal-journal ] [ -E extended_options ] 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 commit‐
ted 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 the device file where the filesystem is stored (e.g. /dev/hdc1).
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 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.
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 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 block 32768.
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 accu‐
rate.
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 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
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 supported:
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 further 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.
-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 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
fied 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.
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 language, please set the the LC_ALL environment variable to C so that the transcript of e2fsck's out‐
put 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 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 filesystem, generated using e2image(8).
See the e2image(8) man page for more details.
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