FSCK(8)             UNIX Programmer's Manual		  FSCK(8)

NAME
     fsck - file system consistency check and interactive repair

SYNOPSIS
     /usr/etc/fsck -p [ filesystem ...	]
     /usr/etc/fsck [ -P ] [ -b block# ] [ -y ] [ -n ] [ filesys-
     tem ] ...

DESCRIPTION
     The first form of fsck preens a standard set of filesystems
     or the specified file systems.  It is normally used in the
     script /etc/rc during automatic reboot.  In this case fsck
     reads the table /etc/fstab to determine which file systems
     to check.	It uses the information there to inspect groups
     of disks in parallel taking maximum advantage of i/o overlap
     to check the file systems as quickly as possible.	Normally,
     the root file system will be checked on pass 1, other
     ``root'' (``a'' partition) file systems on pass 2, other
     small file systems on separate passes (e.g. the ``d'' file
     systems on pass 3 and the ``e'' file systems on pass 4), and
     finally the large user file systems on the last pass, e.g.
     pass 5.  Only partitions in fstab that are mounted ``rw'' or
     ``rq'' and that have non-zero pass number are checked.

     The system takes care that only a restricted class of inno-
     cuous inconsistencies can happen unless hardware or software
     failures intervene.  These are limited to the following:

	  Unreferenced inodes

	  Link counts in inodes too large

	  Missing blocks in the free list

	  Blocks in the free list also in files

	  Counts in the super-block wrong

     These are the only inconsistencies that fsck with the -p
     option will correct; if it encounters other inconsistencies,
     it exits with an abnormal return status and an automatic
     reboot will then fail.  For each corrected inconsistency one
     or more lines will be printed identifying the file system on
     which the correction will take place, and the nature of the
     correction.  After successfully correcting a file system,
     fsck will print the number of files on that file system, the
     number of used and free blocks, and the percentage of frag-
     mentation.

     If sent a QUIT signal, fsck will finish the file system
     checks, then exit with an abnormal return status that causes
     the automatic reboot to fail.  This is useful when you wish
     to finish the file system checks, but do not want the
     machine to come up multiuser.

     Without the -p option, fsck audits and interactively repairs
     inconsistent conditions for file systems. If the file system
     is inconsistent the operator is prompted for concurrence
     before each correction is attempted.  It should be noted
     that some of the corrective actions which are not correct-
     able under the -p option will result in some loss of data.
     The amount and severity of data lost may be determined from
     the diagnostic output.  The default action for each con-
     sistency correction is to wait for the operator to respond
     yes or no.  If the operator does not have write permission
     on the file system fsck will default to a -n action.

     Fsck has more consistency checks than its predecessors
     check, dcheck, fcheck, and icheck combined.

     The following flags are interpreted by fsck.

     -P    This flag forces fsck to check the disk even if the
	   clean flag is set on the disk's superblock.

     -b    Use the block specified immediately after the flag as
	   the super block for the file system.  Block 16 is
	   always an alternate super block.

     -y    Assume a yes response to all questions asked by fsck;
	   this should be used with great caution as this is a
	   free license to continue after essentially unlimited
	   trouble has been encountered.

     -n    Assume a no response to all questions asked by fsck;
	   do not open the file system for writing.

     If no filesystems are given to fsck then a default list of
     file systems is read from the file /etc/fstab.

     Inconsistencies checked are as follows:

     1.    Blocks claimed by more than one inode or the free
	   list.
     2.    Blocks claimed by an inode or the free list outside
	   the range of the file system.
     3.    Incorrect link counts.
     4.    Size checks:
		 Directory size not of proper format.
     5.    Bad inode format.
     6.    Blocks not accounted for anywhere.
     7.    Directory checks:
		 File pointing to unallocated inode.
		 Inode number out of range.
     8.    Super Block checks:

		 More blocks for inodes than there are in the
		 file system.
     9.    Bad free block list format.
     10.   Total free block and/or free inode count incorrect.

     Orphaned files and directories (allocated but unreferenced)
     are, with the operator's concurrence, reconnected by placing
     them in the lost+found directory.	The name assigned is the
     inode number.  If the lost+found directory does not exist,
     it is created.  If there is insufficient space its size is
     increased.

     Checking the raw device is almost always faster.

FILES
     /etc/fstab           contains default list of file systems
			  to check.

DIAGNOSTICS
     The diagnostics produced by fsck are fully enumerated and
     explained in Appendix A of ``Fsck - The UNIX File System
     Check Program'' (SMM:5).

SEE ALSO
     fstab(5), fs(5), newfs(8), mkfs(8), crash(8V), reboot(8)

BUGS
     There should be some way to start a fsck -p at pass n.