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OpenDarwin 7.2.1 - man page for fsck (opendarwin section 8)

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FSCK(8) 			   BSD System Manager's Manual				  FSCK(8)

NAME
     fsck -- filesystem consistency check and interactive repair

SYNOPSIS
     fsck -p [-f] [-m mode]
     fsck [-b block#] [-c level] [-l maxparallel] [-q] [-y] [-n] [-m mode] [filesystem] ...

DESCRIPTION
     The first form of fsck preens a standard set of filesystems or the specified filesystems.
     It is normally used in the script /etc/rc during automatic reboot.  Here fsck reads the ta-
     ble /etc/fstab to determine which filesystems to check.  Only partitions in fstab that are
     mounted ``rw,'' ``rq'' or ``ro'' and that have non-zero pass number are checked.  Filesys-
     tems with pass number 1 (normally just the root filesystem) are checked one at a time.  When
     pass 1 completes, all remaining filesystems are checked, running one process per disk drive.
     The disk drive containing each filesystem is inferred from the longest prefix of the device
     name that ends in a digit; the remaining characters are assumed to be the partition designa-
     tor.  In preening mode, filesystems that are marked clean are skipped.  Filesystems are
     marked clean when they are unmounted, when they have been mounted read-only, or when fsck
     runs on them successfully.

     The kernel takes care that only a restricted class of innocuous filesystem inconsistencies
     can happen unless hardware or software failures intervene.  These are limited to the follow-
     ing:
	   Unreferenced inodes
	   Link counts in inodes too large
	   Missing blocks in the free map
	   Blocks in the free map also in files
	   Counts in the super-block wrong

     These are the only inconsistencies that fsck with the -p option will correct; if it encoun-
     ters 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 identi-
     fying the filesystem on which the correction will take place, and the nature of the correc-
     tion.  After successfully correcting a filesystem, fsck will print the number of files on
     that filesystem, the number of used and free blocks, and the percentage of fragmentation.

     If sent a QUIT signal, fsck will finish the filesystem checks, then exit with an abnormal
     return status that causes an automatic reboot to fail.  This is useful when you want to fin-
     ish the filesystem checks during an automatic reboot, but do not want the machine to come up
     multiuser after the checks complete.

     Without the -p option, fsck audits and interactively repairs inconsistent conditions for
     filesystems.  If the filesystem 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 correctable 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 consistency correction is to wait for the operator to respond yes or no.	If the
     operator does not have write permission on the filesystem 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.

     -b 	 Use the block specified immediately after the flag as the super block for the
		 filesystem.  Block 32 is usually an alternate super block.

     -f 	 Force fsck to check `clean' filesystems when preening.

     -l 	 Limit the number of parallel checks to the number specified in the following
		 argument.  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
		 filesystem at a time.

     -m 	 Use the mode specified in octal immediately after the flag as the permission
		 bits to use when creating the lost+found directory rather than the default 1777.
		 In particular, systems that do not wish to have lost files accessible by all
		 users on the system should use a more restrictive set of permissions such as
		 700.

     -q 	 Do a quick check to determine if the filesystem was unmounted cleanly.

     -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 except for 'CONTINUE?',
		 which is assumed to be affirmative; do not open the filesystem for writing.

     -c 	 Convert the filesystem to the specified level.  Note that the level of a
		 filesystem can only be raised.  There are currently four levels defined:

		 0	       The filesystem is in the old (static table) format.

		 1	       The filesystem is in the new (dynamic table) format.

		 2	       The filesystem supports 32-bit uid's and gid's, short symbolic
			       links are stored in the inode, and directories have an added field
			       showing the file type.

		 3	       If maxcontig is greater than one, build the free segment maps to
			       aid in finding contiguous sets of blocks.  If maxcontig is equal
			       to one, delete any existing segment maps.

		 In interactive mode, fsck will list the conversion to be made and ask whether
		 the conversion should be done.  If a negative answer is given, no further opera-
		 tions are done on the filesystem.  In preen mode, the conversion is listed and
		 done if possible without user interaction.  Conversion in preen mode is best
		 used when all the filesystems are being converted at once.  The format of a
		 filesystem can be determined from the first line of output from dumpfs(8).

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

	   Inconsistencies checked are as follows:
	   1.	Blocks claimed by more than one inode or the free map.
	   2.	Blocks claimed by an inode outside the range of the filesystem.
	   3.	Incorrect link counts.
	   4.	Size checks:
		      Directory size not a multiple of DIRBLKSIZ.
		      Partially truncated file.
	   5.	Bad inode format.
	   6.	Blocks not accounted for anywhere.
	   7.	Directory checks:
		      File pointing to unallocated inode.
		      Inode number out of range.
		      Dot or dot-dot not the first two entries of a directory or having the wrong
		      inode number.
	   8.	Super Block checks:
		      More blocks for inodes than there are in the filesystem.
		      Bad free block map format.
		      Total free block and/or free inode count incorrect.

     Orphaned files and directories (allocated but unreferenced) are, with the operator's concur-
     rence, 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.

     Because of inconsistencies between the block device and the buffer cache, the raw device
     should always be used.

FILES
     /etc/fstab  contains default list of filesystems to check.

DIAGNOSTICS
     The diagnostics produced by fsck are fully enumerated and explained in Appendix A of Fsck -
     The UNIX File System Check Program.

SEE ALSO
     fs(5), fstab(5), newfs(8), reboot(8)

4th Berkeley Distribution		   May 9, 1995			4th Berkeley Distribution
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