fsck - check and repair a Linux file system
SYNOPSIS
fsck [ -sACVRTNP ] [ -t fstype ] filesys [ ... ] [--] [
fsck-options ]
DESCRIPTION
fsck is used to check and optionally repair a one or more
Linux file systems. 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).
The fsck 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 fsck 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 -A option is the bit-wise OR of the exit codes
for each file system that is checked.
In actuality, fsck 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 /sbin
first, then in /etc/fs and /etc, and finally in the direc
tories listed in the PATH environment variable. Please
see the file system-specific checker manual pages for fur
ther details.
OPTIONS
-s Serialize fsck operations. This is a good idea if
you 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 file system to be checked.
When the -A flag is specified, only filesystems
that match fslist are checked. The fslist parame
ter is a comma-separated list of filesystems and
options specifiers. All of the filesystems in this
operator 'no' or '!', which requests that only
those filesystems not listed in fslist will be
checked. If all of the filesystems in fslist are
not prefixed by a negation operator, then only
those filesystems listed in fslist will be checked.
Options specifiers may be included in the comma
separated fslist. They must have the format
opts=fs-option, and may be prefixed by a negation
operator. If an options specifier is present, then
only filesystems whose /etc/fstab entry do (or do
not, if the options specifier was prefixed by a
negation operator) contain fs-option in their
options field of the /etc/fstab file 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 search
ing 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 file system type
(currently ext2) is used.
-A Walk through the /etc/fstab file and try to check
all file systems in one run. This option is typi
cally used from the /etc/rc system initalization
file, instead of multiple commands for checking a
single file system.
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 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.
Hence, a very common configuration in /etc/fstab
fs_passno value of 1 and to set all filesystems to
have a fs_passno value of 2. This will allow fsck
to automatically run filesystem checkers in paral
lel if it is advantageous to do so. System admin
istrators might choose not to use this configura
tion 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.
-C Display completion/progress bars for those filesys
tems checkers (currently only for ext2) which sup
port them. Fsck will manage the filesystem check
ers so that only one of them will display a
progress bar at a time.
-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 solu
tion).
-R When checking all file systems with the -A flag,
skip the root file system (in case it's already
mounted read-write).
-T Don't show the title on startup.
-V Produce verbose output, including all file system-
specific commands that are executed.
fsck-options
Options which 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
arguments take options and which don't.
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 arbi
trarily 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
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.
Currently, standardized file system-specific options are
somewhat in flux. Although not guaranteed, the following
options are supported by most file system checkers:
-a Automatically repair the file system without any
questions (use this option with caution). Note
that e2fsck(8) supports -a for backwards compati
bility only. This option is mapped to e2fsck's -p
option which is safe to use, unlike the -a option
that most file system checkers support.
-r Interactively repair the filesystem (ask for con
firmations). 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 backwards
compatibility reasons only.
AUTHOR
Theodore Ts'o (tytso@mit.edu)
The manual page was shamelessly adapted from David Engel
and Fred van Kempen's generic fsck front end program,
which was in turn shamelessly adapted from Remy Card's
version for the ext2 file system.
FILES
/etc/fstab.
SEE ALSO
fstab(5), mkfs(8), fsck.minix(8), fsck.ext2(8) or
e2fsck(8), fsck.xiafs(8).
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