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 status returned by fsck is the sum of the following conditions:
The exit status returned when multiple filesystems are checked is the bit-wise OR of the exit statuses for each filesystem that is checked.
In actuality, fsck 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 further details.
/dev/sda1: status 0, rss 92828, real 4.002804, user 2.677592, sys 0.86186
GUI front-ends may specify a file descriptor fd, 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
Options specifiers may be included in the comma-separated fslist. They must have the format opts=fs-option. If an options specifier is present, then only filesystems which contain fs-option in their mount options field of /etc/fstab will be checked. If the options specifier is prefixed by a negation operator, then only those filesystems that do not have fs-option in their mount options field of /etc/fstab will be checked.
For example, if opts=ro appears in fslist, then only filesystems listed in /etc/fstab with the ro option 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 searching for filesys in the /etc/fstab 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 -t option, fsck will use the specified filesystem type. If this type is not available, then the default filesystem type (currently ext2) is used.
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.
fsck 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 /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 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.
fsck 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 /etc/fstab mount option nofail may be used to have fsck skip non-existing devices. fsck also skips non-existing devices that have the special filesystem type auto.
These options must not take arguments, as there is no way for fsck to be able to properly guess which options take arguments and which don’t.
Options and arguments which follow the -- are treated as filesystem-specific options to be passed to the filesystem-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 fsck 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 with fsck. Options to different filesystem-specific fsck’s are not standardized.