fsck_ufs(1M)						  System Administration Commands					      fsck_ufs(1M)

NAME

       fsck_ufs - file system consistency check and interactive repair

SYNOPSIS

       fsck -F ufs [generic-options] [special]...

       fsck -F ufs [generic-options] [-o specific-options]
	    [special]...

DESCRIPTION

       The  fsck utility audits and interactively repairs inconsistent conditions on file systems. A file system to be checked may be specified by
       giving the name of the block or character special device or by giving  the  name  of  its  mount  point	if  a  matching  entry	exists	in
       /etc/vfstab.

       The special parameter represents the character special device, for example, /dev/rdsk/c1t0d0s7, on which the file system resides. The char-
       acter special device, not the block special device should be used. The fsck utility will not work if the block device  is  mounted,  unless
       the file system is error-locked.

       If no special device is specified, all ufs file systems specified in the vfstab with a fsckdev entry will be checked. If the -p (``preen'')
       option is specified, ufs file systems with an fsckpass number greater than 1 are checked in parallel. See fsck(1M).

       In the case of correcting serious inconsistencies, by default, fsck asks for confirmation before making a repair and waits for the operator
       to  respond either yes or no. If the operator does not have write permission on the file system, fsck will default to a -n (no corrections)
       action. See fsck(1M).

       Repairing some file system inconsistencies can result in loss of data. The amount and severity of data loss  can  be  determined  from  the
       diagnostic output.

       The  fsck  utility  automatically  corrects innocuous inconsistencies such as unreferenced inodes, too-large link counts in inodes, missing
       blocks in the free list, blocks appearing in the free list and also in files, or incorrect counts in the super block. It displays a message
       for  each inconsistency corrected that identifies the nature of the correction on the file system which took place. After successfully cor-
       recting a file system, fsck prints the number of files on that file system, the number of used and free blocks, and the percentage of frag-
       mentation.

       Inconsistencies checked include:

	   o	  Blocks claimed by more than one inode or the free list.

	   o	  Blocks claimed by an inode or the free list outside the range of the file system.

	   o	  Incorrect link counts.

	   o	  Incorrect directory sizes.

	   o	  Bad inode format.

	   o	  Blocks not accounted for anywhere.

	   o	  Directory  checks,  file  pointing to unallocated inode, inode number out of range, and absence of `.' and `..' as the first two
		  entries in each directory.

	   o	  Super Block checks: more blocks for inodes than there are in the file system.

	   o	  Bad free block list format.

	   o	  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 insuf-
       ficient space in the lost+found directory, its size is increased.

       An attempt to mount a ufs file system with the -o nolargefiles option will fail if the file system has ever contained a large file (a  file
       whose  size is greater than or equal to 2 Gbyte). Invoking fsck resets the file system state if no large files are present in the file sys-
       tem. A successful mount of the file system after invoking fsck indicates the absence of large files in the  file  system.  An  unsuccessful
       mount attempt indicates the presence of at least one large file. See mount_ufs(1M).

OPTIONS

       The generic-options consist of the following options:

       -m	   Check  but do not repair. This option checks that the file system is suitable for mounting, returning the appropriate exit sta-
		   tus. If the file system is ready for mounting, fsck displays a message such as:

		       ufs fsck: sanity check: /dev/rdsk/c0t3d0s1 okay

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

       -V	   Echo the expanded command line, but do not execute the command. This option may be used to verify and to validate  the  command
		   line.

       -v	   Enables verbose output. Might not be supported by all filesystem-specific fsck implementations.

       -y|Y	   Assume a yes response to all questions asked by fsck.

       See generic fsck(1M) for the details for specifying special.

       -o specific-options    Specify  ufs file system specific options. These options can be any combination of the following separated by commas
			      (with no intervening spaces).

			      b=n    Use block n as the super block for the file system. Block 32 is always one of  the  alternate  super  blocks.
				     Determine the location of other super blocks by running newfs(1M) with the -Nv options specified.

			      f      Force checking of file systems regardless of the state of their super block clean flag.

			      p      Check  and  fix the file system non-interactively ("preen"). Exit immediately if there is a problem requiring
				     intervention. This option is required to enable parallel file system checking.

			      w      Check writable file systems only.

FILES

       /etc/vfstab    list of default parameters for each file system

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Availability		     |SUNWcsu			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       clri(1M), fsck(1M), fsdb_ufs(1M), fsirand(1M), fstyp(1M),  mkfs(1M),  mkfs_ufs(1M),  mount_ufs(1M),  mountall(1M),  newfs(1M),  reboot(1M),
       vfstab(4), attributes(5), largefile(5), ufs(7FS)

WARNINGS

       The operating system buffers file system data. Running fsck on a mounted file system can cause the operating system's buffers to become out
       of date with respect to the disk. For this reason, the file system should be unmounted when fsck is used. If this  is  not  possible,  care
       should  be taken that the system is quiescent and that it is rebooted immediately after fsck is run. Quite often, however, this will not be
       sufficient. A panic will probably occur if running fsck on a file system modifies the file system.

NOTES

       It is usually faster to check the character special device than the block special device.

       Running fsck on file systems larger than 2 Gb fails if the user chooses to use the block interface to the device:

       fsck /dev/dsk/c?t?d?s?

       rather than the raw (character special) device:

       fsck /dev/rdsk/c?t?d?s?

SunOS 5.11							    2 Aug 2005							      fsck_ufs(1M)