Provided by: e2fsprogs_1.47.0-2.4~exp1ubuntu4.1_amd64 
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 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.
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 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.
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 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.
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)