fsck.ext2(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 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 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 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
accurate.
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 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
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 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
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.
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 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.
-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
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
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 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 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.
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)
Opportunity
Personal Opportunity - Free software gives you access to billions of dollars of software at no cost. Use this software for your business, personal use or to develop a profitable skill. Access to source code provides access to a level of capabilities/information that companies protect though copyrights. Open source is a core component of the Internet and it is available to you. Leverage the billions of dollars in resources and capabilities to build a career, establish a business or change the world. The potential is endless for those who understand the opportunity.
Business Opportunity - Goldman Sachs, IBM and countless large corporations are leveraging open source to reduce costs, develop products and increase their bottom lines. Learn what these companies know about open source and how open source can give you the advantage.
Free Software
Free Software provides computer programs and capabilities at no cost but more importantly, it provides the freedom to run, edit, contribute to, and share the software. The importance of free software is a matter of access, not price. Software at no cost is a benefit but ownership rights to the software and source code is far more significant.
Free Office Software - The Libre Office suite provides top desktop productivity tools for free. This includes, a word processor, spreadsheet, presentation engine, drawing and flowcharting, database and math applications. Libre Office is available for Linux or Windows.
Free Books
The Free Books Library is a collection of thousands of the most popular public domain books in an online readable format. The collection includes great classical literature and more recent works where the U.S. copyright has expired. These books are yours to read and use without restrictions.
Source Code - Want to change a program or know how it works? Open Source provides the source code for its programs so that anyone can use, modify or learn how to write those programs themselves. Visit the GNU source code repositories to download the source.
Education
Study at Harvard, Stanford or MIT - Open edX provides free online courses from Harvard, MIT, Columbia, UC Berkeley and other top Universities. Hundreds of courses for almost all major subjects and course levels. Open edx also offers some paid courses and selected certifications.
Linux Manual Pages - A man or manual page is a form of software documentation found on Linux/Unix operating systems. Topics covered include computer programs (including library and system calls), formal standards and conventions, and even abstract concepts.
