Section 8: fsck
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man pages.
FSCK(8) FSCK(8)
NAME
fsck - check and repair a Linux file system
SYNOPSIS
fsck [ -sACVRTNP ] [ -t fstype ] [--] [ fsck-options ]
filesys [ ... ]
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 fstype
Specifies the type of file system to be checked.
When the -A flag is specified, only filesystems
that match fstype are checked. If fstype is pre-
fixed with no then only filesystems whose type does
not match fstype are checked.
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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, fsck will use the type specified by the -t
option if it specifies a unique 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. If there are multiple filesystems
with the same pass number, e2fsck will attempt to
check them in parallel, although it will avoid run-
ning multiple filesystem checks on the same physi-
cal disk. 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 filesys-
tems 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 config-
uration 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
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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
Any options which are not understood by fsck, or
which follow the -- option are treated as file sys-
tem-specific options to be passed to the file sys-
tem-specific checker.
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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