Section: System Administration (8)
Updated: February 2009
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fsck - check and repair a Linux filesystem
is used to check and optionally repair one or more Linux filesystems.
can be a device name (e.g.
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).
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
option is not specified,
will default to checking filesystems in
serially. This is equivalent to the
The exit code returned by
is the sum of the following conditions:
Filesystem errors corrected
System should be rebooted
Filesystem errors left uncorrected
Usage or syntax error
Checking canceled by user request
The exit code returned when multiple filesystems are checked
is the bit-wise OR of the exit codes for each
filesystem that is checked.
is simply a front-end for the various filesystem checkers
(fsck.fstype) available under Linux. The
filesystem-specific checker is searched for in the
PATH environment variable. If the PATH is undefined then
fallback to "/sbin".
Please see the filesystem-specific checker manual pages for
Create an exclusive
lock file (/run/fsck/<diskname>.lock) for whole-disk device.
This option can be used with one device only (this means that -A and
-l are mutually exclusive). This option is recommended when more
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.
- -r [fd]
Report certain statistics for each fsck when it completes. These statistics
include the exit status, the maximum run set size (in kilobytes), the elapsed
all-clock time and the user and system CPU time used by the fsck run. For
/dev/sda1: status 0, rss 92828, real 4.002804, user 2.677592, sys 0.86186
GUI front-ends may specify a file descriptor
in which case the progress bar information will be sent to that file descriptor
in a machine parsable format. For example:
/dev/sda1 0 92828 4.002804 2.677592 0.86186
operations. This is a good idea if you are checking multiple
filesystems and the checkers are in an interactive mode. (Note:
runs in an interactive mode by default. To make
run in a non-interactive mode, you must either specify the
option, if you wish for errors to be corrected automatically, or the
option if you do not.)
- -t fslist
Specifies the type(s) of filesystem to be checked. When the
flag is specified, only filesystems that match
are checked. The
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
which requests that only those filesystems not listed in
will be checked. If none of the filesystems in
is prefixed by a negation operator, then only those listed filesystems
will be checked.
Options specifiers may be included in the comma-separated
They must have the format
If an options specifier is present, then only filesystems which contain
in their mount options field of
will be checked. If the options specifier is prefixed by a negation
operator, then only
those filesystems that do not have
in their mount options field of
will be checked.
For example, if
then only filesystems listed in
option will be checked.
For compatibility with Mandrake distributions whose boot scripts
depend upon an unauthorized UI change to the
program, if a filesystem type of
is found in
it is treated as if
were specified as an argument to the
Normally, the filesystem type is deduced by searching for
file and using the corresponding entry.
If the type cannot be deduced, and there is only a single filesystem
given as an argument to the
will use the specified filesystem type. If this type is not
available, then the default filesystem type (currently ext2) is used.
Walk through the
file and try to check all filesystems in one run. This option is
typically used from the
system initialization file, instead of multiple commands for checking
a single filesystem.
The root filesystem will be checked first unless the
option is specified (see below). After that,
filesystems will be checked in the order specified by the
(the sixth) field in the
Filesystems with a
value of 0 are skipped and are not checked at all. Filesystems with a
value of greater than zero will be checked in order,
with filesystems with the lowest
number being checked first.
If there are multiple filesystems with the same pass number,
will attempt to check them in parallel, although it will avoid running
multiple filesystem checks on the same physical disk.
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 determine dependencies between devices.
Hence, a very common configuration in
files is to set the root filesystem to have a
value of 1
and to set all other filesystems to have a
value of 2. This will allow
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.
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
may be used to have
skip non-existing devices.
also skips non-existing devices that have the special filesystem type
- -C [fd]
Display completion/progress bars for those filesystem checkers (currently
only for ext) 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
in which case the progress bar information will be sent to that file descriptor.
Do not check mounted filesystems and return an exit code of 0
for mounted filesystems.
Don't execute, just show what would be done.
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
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).
When checking all filesystems with the
flag, skip the root filesystem. (This is useful in case the root
filesystem has already been mounted read-write.)
Don't show the title on startup.
Produce verbose output, including all filesystem-specific commands
that are executed.
- -?, --help
Display help text and exit.
Display version information and exit.
FILESYSTEM SPECIFIC OPTIONS
Options which are not understood by fsck are passed to the filesystem-specific checker!
not take arguments, as there is no
to be able to properly guess which options take arguments and which
Options and arguments which follow the
are treated as filesystem-specific options to be passed to the
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
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
Options to different filesystem-specific fsck's are not standardized.
program's behavior is affected by the following environment variables:
If this environment variable is set,
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.
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
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
may attempt to automatically determine how many filesystem checks can
be run based on gathering accounting data from the operating system.
environment variable is used to find filesystem checkers.
This environment variable allows the system administrator
to override the standard location of the
file. It is also useful for developers who are testing
enables libblkid debug output.
enables libmount debug output.
Theodore Ts'o <firstname.lastname@example.org>
Karel Zak <email@example.com>
The fsck command is part of the util-linux package and is available from
Linux Kernel Archive
- FILESYSTEM SPECIFIC OPTIONS
- ENVIRONMENT VARIABLES
- SEE ALSO
This document was created by
using the manual pages.
Time: 03:06:06 GMT, September 19, 2018