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 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 indi-
cates 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 filesys-
tems. 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.
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 filesystem. A response of 'y' will fix the error; 'n'
will leave the error unfixed; and 'a' will fix the problem and all sub-
sequent problems; pressing Enter will proceed with the default
response, which is printed before the question mark. Pressing Control-
C terminates e2fsck immediately.
OPTIONS
-a This option does the same thing as the -p option. It is pro-
vided 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 loca-
tion 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. block-
size, 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 appropriately upon completion of the
filesystem check.
-B blocksize
Normally, e2fsck will search for the superblock at various dif-
ferent 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 particu-
lar blocksize. If the superblock is not found, e2fsck will ter-
minate 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 direc-
tory. 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 pro-
grams 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 optimize all directories, either by reindexing them if
the filesystem supports directory indexing, or by sorting and
compressing directories for smaller directories, or for filesys-
tems 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 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 sepa-
rated, 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 per-
form any further checks or repairs.
fragcheck
During pass 1, print a detailed report of any dis-
contiguous 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 elimi-
nating 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 propor-
tional 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 opti-
mization 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 filesys-
tem); 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.
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 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 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 filesys-
tem 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 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 system administrator
to take additional corrective action, e2fsck will print a
description of the problem and then exit with the value 4 logi-
cally 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 back-
wards 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.
EXIT CODE
The exit code returned by e2fsck is the sum of the following condi-
tions:
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 tran-
script 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 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.
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 AT mit.edu>.
SEE ALSO
e2fsck.conf(5), badblocks(8), dumpe2fs(8), debugfs(8), e2image(8),
mke2fs(8), tune2fs(8)
E2fsprogs version 1.45.6 March 2020 E2FSCK(8)
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