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Section: Maintenance Commands (8)
Updated: March 2002
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fsck - check and repair a Linux file system
filesys [ ... ]
is used to check and optionally repair a one or more Linux file systems.
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 run filesystems on different physical disk drives
in parallel to reduce total amount time to check all of the filesystems.
The exit code returned by
is the sum of the following conditions:
0 - No errors
1 - File system errors corrected
2 - System should be rebooted
4 - File system errors left uncorrected
8 - Operational error
16 - Usage or syntax error
128 - Shared library error
The exit code returned when all file systems are checked using the
option is the bit-wise OR of the exit codes for each
file system that is checked.
is simply a front-end for the various file system checkers
(fsck.fstype) available under Linux. The file
system-specific checker is searched for in
first, then in
and finally in the directories listed in the PATH environment
variable. Please see the file system-specific checker manual pages for
operations. This is a good idea if you 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 file system 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 all of the filesystems in
are not prefixed by a negation operator, then only those filesystems
will be checked.
Options specifiers may be included in the comma separated
They must have the format
and may be prefixed by a negation operator. If an options specifier is
present, then only filesystems whose
entry do (or do not, if the options specifier was prefixed by a negation
in their options field of the
file 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 can not 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 file system type (currently ext2) is used.
Walk through the
file and try to check all file systems in one run. This option is
typically used from the
system initalization file, instead of multiple commands for checking
a single file system.
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,
fsck will attempt to check them in parallel, although it will avoid running
multiple filesystem checks on the same physical disk.
Hence, a very common configuration in
files is to set the root filesystem to have a
value of 1
and to set all 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.
Display completion/progress bars for those filesystems checkers (currently
only for ext2) which support them. Fsck will manage the filesystem checkers
so that only one of them will display a progress bar at a time.
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 file systems with the
flag, skip the root file system (in case it's already mounted read-write).
Don't show the title on startup.
Produce verbose output, including all file system-specific commands
that are executed.
Options which which are not understood by
are passed to the filesystem-specific checker. These arguments
not take arguments, as there is no
to be able to properly guess which arguments take options and which
Options and arguments which follow the
are treated as file system-specific options to be passed to the
file system-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
some horribly complicated option 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
Currently, standardized file system-specific options are somewhat in
flux. Although not guaranteed, the following options are supported
by most file system checkers:
Automatically repair the file system without any questions (use
this option with caution). Note that
for backwards compatibility only. This option is mapped to
option which is safe to use, unlike the
option that most file system checkers support.
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
default behavior; it supports this option for backwards compatibility
Theodore Ts'o (firstname.lastname@example.org)
program's behavior is affected by the following environment variables:
If this environment variable is set,
will attempt to run 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.)
This environment variable will limit the maximum number of file system
checkers that can be running at one time. This allows configurations
which have a large number of disks to avoid
starting too many file system 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 file system checks can
be run based on gathering accounting data from the operating system.
environment variable is used to find file system checkers. A set of
system directories are searched first:
Then the set of directories found in the
environment are searched.
This environment variable allows the system administrator
to override the standard location of the
file. It is also use for developers who are testing
- ENVIRONMENT VARIABLES
- SEE ALSO
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