fsck – Filesystem consistency check and repair
The fsck program is a frontend to filesystem-specific tools such as e2fsck and fsck.jfs. By whatever name, these programs examine a file system’s major data structures for internal consistency and can correct
Generally, fsck is run automatically at boot time
The following example checks the file system on the first partition of the second hard disk on a Linux system:
The following example checks the JFS file system on a mdadm software raid device:
fsck [ -sAVRTNP ] [ -C [ fd ] ] [ -t fstype ] [filesys ... ] [--] [ fs- specific-options ]
fsck is used to check and optionally repair one or more Linux file sys- tems. 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). Nor- mally, 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 the filesystems. 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 - File system errors corrected 2 - System should be rebooted 4 - File system 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 file systems are checked 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 directories listed in the PATH environment variable. Please see the file system-specific checker manual pages for further details.
-s Serialize fsck operations. This is a good idea if you are checking multiple filesystems and the checkers are in an inter- active 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 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 all of the filesystems in 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 sin- gle filesystem given as an argument to the -t option, fsck will use the specified filesystem type. If this type is not avail- able, then the default file system type (currently ext2) is used. -A Walk through the /etc/fstab file and try to check all file sys- tems in one run. This option is typically used from the /etc/rc system initialization 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 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 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 mul- tiple 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 [ 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 spec- ify a file descriptor fd, in which case the progress bar infor- mation will be sent to that file descriptor. -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 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 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 arbitrarily com- plicated 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 com- plicated option and arguments, and it doesn't do what you expect, don't bother reporting it as a bug. You're almost cer- tainly 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 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 compatibility only. This option is mapped to e2fsck's -p option which is safe to use, unlike the -a option that some file system 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 backwards 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 particu- lar fsck.minix(8) and fsck.cramfs(8) does not support the -y option as of this writing.