NAME¶
fsck - check and repair a Linux filesystem
SYNOPSIS¶
fsck [
-lsAVRTMNP] [
-C [
fd]] [
-t
fstype] [
filesys...] [
--] [
fs-specific-options]
DESCRIPTION¶
fsck is used to check and optionally repair one or more Linux
filesystems.
filesys can be a device name (e.g.
/dev/hdc1,
/dev/sdb2), a mount point (e.g.
/,
/usr,
/home),
or an ext2 label or UUID specifier (e.g.
UUID=8868abf6-88c5-4a83-98b8-bfc24057f7bd or LABEL=root). Normally, the
fsck program will try to handle filesystems on different physical disk
drives in parallel to reduce the total amount of time needed to check all of
them.
If no filesystems are specified on the command line, and the
-A option is
not specified,
fsck will default to checking filesystems in
/etc/fstab serially. This is equivalent to the
-As options.
The exit code returned by
fsck is the sum of the following conditions:
0 - No errors
1 - Filesystem errors corrected
2 - System should be rebooted
4 - Filesystem errors left uncorrected
8 - Operational error
16 - Usage or syntax error
32 - Fsck canceled by user request
128 - Shared-library error
The exit code returned when multiple filesystems are checked is the bit-wise OR
of the exit codes for each filesystem that is checked.
In actuality,
fsck is simply a front-end for the various filesystem
checkers (
fsck.
fstype) available under Linux. The
filesystem-specific checker is searched for in
/sbin first, then in
/etc/fs and
/etc, and finally in the directories listed in the
PATH environment variable. Please see the filesystem-specific checker manual
pages for further details.
OPTIONS¶
- -l
- Lock the whole-disk device by an exclusive flock(2).
This option can be used with one device only (this means that -A
and -l are mutually exclusive). This option is recommended when
more fsck (8) instances are executed in the same time. The option
is ignored when used for multiple devices or for non-rotating disks.
fsck does not lock underlying devices when executed to check
stacked devices (e.g. MD or DM) -- this feature is not implemented
yet.
- -s
- Serialize fsck operations. This is a good idea if
you are checking multiple filesystems and the checkers are in an
interactive mode. (Note: e2fsck(8) runs in an interactive mode by
default. To make e2fsck(8) run in a non-interactive mode, you must
either specify the -p or -a option, if you wish for errors
to be corrected automatically, or the -n option if you do
not.)
- -t fslist
- Specifies the type(s) of filesystem to be checked. When the
-A flag is specified, only filesystems that match fslist are
checked. The fslist parameter is a comma-separated list of
filesystems and options specifiers. All of the filesystems in this
comma-separated list may be prefixed by a negation operator 'no' or
'!', which requests that only those filesystems not listed in
fslist will be checked. If none of the filesystems in fslist
is prefixed by a negation operator, then only those listed filesystems
will be checked.
Options specifiers may be included in the comma-separated fslist.
They must have the format opts=fs-option. If an options
specifier is present, then only filesystems which contain fs-option
in their mount options field of /etc/fstab will be checked. If the
options specifier is prefixed by a negation operator, then only those
filesystems that do not have fs-option in their mount options field
of /etc/fstab will be checked.
For example, if opts=ro appears in fslist, then only
filesystems listed in /etc/fstab with the ro option will be
checked.
For compatibility with Mandrake distributions whose boot scripts depend upon
an unauthorized UI change to the fsck program, if a filesystem type
of loop is found in fslist, it is treated as if
opts=loop were specified as an argument to the -t option.
Normally, the filesystem type is deduced by searching for filesys in
the /etc/fstab file and using the corresponding entry. If the type
can not be deduced, and there is only a single filesystem given as an
argument to the -t option, fsck will use the specified
filesystem type. If this type is not available, then the default
filesystem type (currently ext2) is used.
- -A
- Walk through the /etc/fstab file and try to check
all filesystems in one run. This option is typically used from the
/etc/rc system initialization file, instead of multiple commands
for checking a single filesystem.
The root filesystem will be checked first unless the -P option is
specified (see below). After that, filesystems will be checked in the
order specified by the fs_passno (the sixth) field in the
/etc/fstab file. Filesystems with a fs_passno value of 0 are
skipped and are not checked at all. Filesystems with a fs_passno
value of greater than zero will be checked in order, with filesystems with
the lowest fs_passno number being checked first. If there are
multiple filesystems with the same pass number, fsck will attempt to check
them in parallel, although it will avoid running multiple filesystem
checks on the same physical disk.
fsck does not check stacked devices (RAIDs, dm-crypt, ...) in
parallel with any other device. See below for FSCK_FORCE_ALL_PARALLEL
setting. The /sys filesystem is used to detemine dependencies between
devices.
Hence, a very common configuration in /etc/fstab files is to set the
root filesystem to have a fs_passno value of 1 and to set all other
filesystems to have a fs_passno value of 2. This will allow
fsck to automatically run filesystem checkers in parallel if it is
advantageous to do so. System administrators might choose not to use this
configuration if they need to avoid multiple filesystem checks running in
parallel for some reason --- for example, if the machine in question is
short on memory so that excessive paging is a concern.
fsck normally does not check whether the device actually exists
before calling a filesystem specific checker. Therefore non-existing
devices may cause the system to enter filesystem repair mode during boot
if the filesystem specific checker returns a fatal error. The
/etc/fstab mount option nofail may be used to have
fsck skip non-existing devices. fsck also skips non-existing
devices that have the special filesystem type auto
- -C [ fd ]
- Display completion/progress bars for those filesystem
checkers (currently only for ext2 and ext3) which support them. Fsck will
manage the filesystem checkers so that only one of them will display a
progress bar at a time. GUI front-ends may specify a file descriptor
fd, in which case the progress bar information will be sent to that
file descriptor.
- -M
- Do not check mounted filesystems and return an exit code of
0 for mounted filesystems.
- -N
- Don't execute, just show what would be done.
- -P
- When the -A flag is set, check the root filesystem
in parallel with the other filesystems. This is not the safest thing in
the world to do, since if the root filesystem is in doubt things like the
e2fsck(8) executable might be corrupted! This option is mainly
provided for those sysadmins who don't want to repartition the root
filesystem to be small and compact (which is really the right
solution).
- -R
- When checking all filesystems with the -A flag, skip
the root filesystem. (This is useful in case the root filesystem has
already been mounted read-write.)
- -T
- Don't show the title on startup.
- -V
- Produce verbose output, including all filesystem-specific
commands that are executed.
- fs-specific-options
- Options which are not understood by fsck are passed
to the filesystem-specific checker. These arguments must not take
arguments, as there is no way for fsck to be able to properly guess
which options take arguments and which don't.
- Options and arguments which follow the -- are
treated as filesystem-specific options to be passed to the
filesystem-specific checker.
- Please note that fsck is not designed to pass arbitrarily
complicated options to filesystem-specific checkers. If you're doing
something complicated, please just execute the filesystem-specific checker
directly. If you pass fsck some horribly complicated options and
arguments, and it doesn't do what you expect, don't bother reporting it
as a bug. You're almost certainly doing something that you shouldn't
be doing with fsck.
Options to different filesystem-specific fsck's are not standardized. If in
doubt, please consult the man pages of the filesystem-specific checker.
Although not guaranteed, the following options are supported by most
filesystem checkers:
- -a
- Automatically repair the filesystem without any questions
(use this option with caution). Note that e2fsck(8) supports
-a for backward compatibility only. This option is mapped to
e2fsck's -p option which is safe to use, unlike the
-a option that some filesystem checkers support.
- -n
- For some filesystem-specific checkers, the -n option
will cause the fs-specific fsck to avoid attempting to repair any
problems, but simply report such problems to stdout. This is however not
true for all filesystem-specific checkers. In particular,
fsck.reiserfs(8) will not report any corruption if given this
option. fsck.minix(8) does not support the -n option at
all.
- -r
- Interactively repair the filesystem (ask for
confirmations). Note: It is generally a bad idea to use this option if
multiple fsck's are being run in parallel. Also note that this is
e2fsck's default behavior; it supports this option for backward
compatibility reasons only.
- -y
- For some filesystem-specific checkers, the -y option
will cause the fs-specific fsck to always attempt to fix any detected
filesystem corruption automatically. Sometimes an expert may be able to do
better driving the fsck manually. Note that not all
filesystem-specific checkers implement this option. In particular
fsck.minix(8) and fsck.cramfs(8) do not support the
-y option as of this writing.
AUTHOR¶
Theodore Ts'o (tytso@mit.edu)
AVAILABILITY¶
The fsck command is part of the util-linux package and is available from
ftp://ftp.kernel.org/pub/linux/utils/util-linux/.
FILES¶
/etc/fstab.
ENVIRONMENT VARIABLES¶
The
fsck program's behavior is affected by the following environment
variables:
- FSCK_FORCE_ALL_PARALLEL
- If this environment variable is set, fsck will
attempt to check all of the specified filesystems in parallel, regardless
of whether the filesystems appear to be on the same device. (This is
useful for RAID systems or high-end storage systems such as those sold by
companies such as IBM or EMC.) Note that the fs_passno value is still
used.
- FSCK_MAX_INST
- This environment variable will limit the maximum number of
filesystem checkers that can be running at one time. This allows
configurations which have a large number of disks to avoid fsck
starting too many filesystem checkers at once, which might overload CPU
and memory resources available on the system. If this value is zero, then
an unlimited number of processes can be spawned. This is currently the
default, but future versions of fsck may attempt to automatically
determine how many filesystem checks can be run based on gathering
accounting data from the operating system.
- PATH
- The PATH environment variable is used to find
filesystem checkers. A set of system directories are searched first:
/sbin, /sbin/fs.d, /sbin/fs, /etc/fs, and
/etc. Then the set of directories found in the PATH
environment are searched.
- FSTAB_FILE
- This environment variable allows the system administrator
to override the standard location of the /etc/fstab file. It is
also useful for developers who are testing fsck.
SEE ALSO¶
fstab(5),
mkfs(8),
fsck.ext2(8) or
fsck.ext3(8) or
e2fsck(8),
cramfsck(8),
fsck.minix(8),
fsck.msdos(8),
fsck.jfs(8),
fsck.nfs(8),
fsck.vfat(8),
fsck.xfs(8),
fsck.xiafs(8),
reiserfsck(8).