Generic fsck Command Syntax, Options, and Arguments
The fsck command has two components: a generic component and a component specific
to each type of file system. The generic commands apply to most types of file systems, while the specific
commands apply to only one type of file system. You should always use the generic command, which calls
the file system-specific command, as needed.
Usually, you must be superuser to run fsck. You can run the fsck
command without being superuser; but to make repairs, you should unmount the file system and you must
have read permission for the raw device file for the slice (a potential security hole).
The generic fsck command goes through /etc/vfstab to see
what file systems to check. It runs the appropriate file system-specific fsck command
on each file system listed, except those excluded by an fsck pass number of - or 0 (UFS only).
The generic fsck command has the following syntax:
/usr/sbin/fsck [-F type] [-V] [-m] [special]
/usr/sbin/fsck [-F type] [-V] -[y|Y]|[n|N] [-o specific-options][special]
|
Table 31-4 describes the options and arguments
to the generic fsck command.
Table 31-4
The
fsck Command
Options and Arguments
Option Type
|
Option
|
Description
|
Generic
|
-F
|
Specifies the file system type (type).
If type is not specified on the command line, it is obtained from /etc/vfstab by matching an entry in that
file with the special device name specified. If no entry is found, the default local file system type
specified in /etc/default/fs is used.
|
|
-V
|
Echoes the completed command line (verbose). The echoed line includes
additional information derived from /etc/vfstab. This option can be used to verify
and validate the command line. It does not execute the command.
|
|
-m
|
Performs a preliminary
check only. It returns a code indicating the state of the file system: 0 for "clean"
and 32 for "dirty." This option is used by the startup script /sbin/rcS to determine whether a file system needs to be checked.
|
|
-y or -Yor -n or -N
|
Runs the command automatically answering yes or no to all prompts.
|
|
c
|
Converts an old format file system with
statically allocated tables to new format dynamically allocated tables. Static allocation imposes a hard
maximum on table size, while dynamic allocation
means space for tables can be added as needed after the initial allocation. If the file system is in the
new format, convert it to the old format, unless the table allocation exceeds the fixed maximum allowed
in the old format. fsck lists the direction of the conversion. In interactive mode, fsck prompts for confirmation before doing the conversion. When you use the -o p
option, the conversion is attempted without asking for confirmation. This option is useful when you want
to covert a number of file systems at once. You can determine whether a file
system is in the old or new format by running the fstyp(1M) command, and looking at
the first line displayed.
|
|
w
|
Checks only file systems that permit write access.
|
|
special
|
Specifies the mount point or raw device name of one or more file systems. An entry
for the mount point must exist in /etc/vfstab. If you omit the special argument, entries in /etc/vfstab with a
specified fsck device and a fsck pass number greater than zero are
checked. If preening (-o p) is in effect and more than one entry has an fsck
pass number greater than 1, file systems on different disks are checked in parallel.
|
Specific
|
|
This is a comma-separated list of options that follow the -o option.
Describes the options that are passed to the UFS-specific fsck command for interpretation.
|
|
p
|
Preens. Runs the command automatically
in silent mode, correcting what it can, but exiting when it encounters a problem that requires intervention.
This option also enables parallel checking of UFS file systems.
|
|
b=blocknumber
|
Uses the alternative (redundant)
superblock, located
at the specified location. This option can be used to repair a bad superblock. You can display a list
of alternative superblocks by using the newfs -N command.
|