command invokes file-system-specific programs to check the
special devices listed in the
file or on the command line for consistency.
It is normally used in the script
during automatic reboot.
If no file systems are specified,
reads the file
to determine which file systems to check and in what order.
Only partitions in fstab that are mounted
and that have non-zero pass numbers are checked.
File systems with pass number 1 (normally just the root file system) are
checked one at a time.
When pass 1 completes, all remaining file systems are checked, with one
process spawned per disk drive.
The disk drive containing each file system is inferred from the longest
prefix of the device name that ends in a digit; the remaining characters
are assumed to be the partition designator.
By default, file systems which are already mounted read/write are not
The options are as follows:
to use the specified block as the location of the superblock.
Block 32 is usually an alternate super block.
This option is only valid for filesystems that support backup superblocks
(ffs and ext2fs).
Just print the commands without executing them.
Available only if
is compiled to support it.
Force checking of file systems, even when they are marked clean (for file systems
that support this).
Limit the number of parallel checks to
By default, the limit is the number of
disks, running one process per disk.
If a smaller limit is given,
the disks are checked round-robin, one file system at a time.
response to all questions asked by
which is assumed to be affirmative.
File systems will not be opened for writing.
This is the default for file systems to be checked that are
concurrently mounted writable.
Enter preen mode:
will check all file systems listed in
according to their pass number,
or any special devices listed on the command line,
and will make minor repairs without
Any major problems will cause
to exit with a non-zero exit code,
so as to alert any invoking program or script
that human intervention is required.
List of comma separated file system specific options for the specified
file system type, in the same format as
only for the comma separated list of file system types.
If the list starts with
only in the file system types that are
Print the commands before executing them.
as the answer to all operator questions.
If neither of the
options are specified, the user may force
to assume an answer of
to all the remaining questions by replying to a question with a value of