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 fsck_hfs(1M)							fsck_hfs(1M)




 NAME
      fsck - HFS file system consistency check and interactive repair

 SYNOPSIS
      /usr/sbin/fsck [-F hfs] [-m] [-V] [-b blocknum] [special ...]

      /usr/sbin/fsck [-F hfs] [-c size] [-f] [-p|-P] [-V] [special ...]

      /usr/sbin/fsck [-F hfs] [-b blocknum] [-c size] [-f] [-n|-N|-y|-Y]
	   [-q] [-V] [special ...]

 DESCRIPTION
      The fsck command audits and repairs inconsistent conditions for HFS
      file systems on mass storage device files identified by special.	If
      the file system is consistent, the number of files on that file system
      and the number of used and free blocks are reported.  If the file
      system is inconsistent, fsck provides a mechanism to fix these
      inconsistencies, depending on which form of the fsck command is used.

      special represents a special device (e.g., /dev/rdsk/c1d0s8).

      If the target device is a swap device, fsck does not continue to
      process.	fsck also checks the target device to ensure a mounted file
      system is not being checked.  If a mounted device is specified but the
      -f option is omitted, fsck prompts the user for a response.

      If the -p|-P option is used and special is not specified, fsck reads
      the pass numbers in /etc/fstab to determine which groups of disks to
      inspect in parallel, taking maximum advantage of I/O overlap to
      process the file systems as quickly as possible.	The -p|-P option is
      normally used in the script /sbin/bcheckrc during automatic reboot.

      Normally, the root file system is checked on pass 1, and other "root"
      (section 0) file systems on pass 2.  Other small file systems are
      checked on separate passes (such as the section 4 file systems on pass
      3 and the section 7 file systems on pass 4), and finally the large
      user file systems are checked on the last pass (for example, pass 5).
      A pass number of 0 in /etc/fstab causes a file system not to be
      checked.	If the optional fields are not present on a line in
      /etc/fstab, fsck processes the file system on such lines sequentially
      after all eligible file systems with positive pass numbers have been
      processed.

      The inconsistencies that fsck with the -p|-P option corrects are shown
      below.  These are inconsistencies that are correctable without data
      loss.  If it encounters other inconsistencies, it exits with an
      abnormal return status.  For each corrected inconsistency, one or more
      lines are printed identifying the file system on which the correction
      will take place and the nature of the correction.	 Correctable
      inconsistencies are limited to the following:




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	   +  Unreferenced inodes
	   +  Unreferenced continuation inodes (see inode(4))
	   +  Unreferenced pipes and FIFOs
	   +  Link counts in inodes too large
	   +  Missing blocks in the free list
	   +  Blocks in the free list also in files
	   +  Counts in the superblock wrong.

      The -P option operates in the same manner as the -p option except that
      cleanly unmounted file systems are not checked (see fsclean(1M)).
      This can greatly decrease the amount of time required to reboot a
      system that was brought down cleanly.

      If the -p|-P option is not specified, the pass numbers are ignored and
      the file systems are checked interactively in the order they are
      listed in /etc/fstab.

      Without the -p|-P option, fsck prompts for concurrence before each
      correction is attempted when the file system is inconsistent.  It
      should be noted that some corrective actions result in a loss of data.
      The amount and severity of data loss can 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, fsck defaults to a -n action.

    Options
      fsck recognizes the following options:

	   -F hfs    Specify the HFS file system.

	   -c size   Set the size of the buffer cache which fsck uses to
		     cache disk blocks.	 size is the number of cache blocks,
		     and is between 0 and 100 inclusive.  The most common
		     use of this option is -c 0 to disable all caches, thus
		     reducing memory usage.

	   -b blocknum
		     Use the specified blocknum as the superblock for the
		     file system.  An alternate superblock can usually be
		     found at block ((SBSIZE+BBSIZE)/DEV_BSIZE), typically
		     block 16.	DEV_BSIZE is defined in <&lt&lt&lt;sys/param.h>&gt&gt&gt;.	You
		     can also find a list of alternate superblocks in
		     /var/adm/sbtab (see mkfs(1M)).

	   -f	     Force fsck to check a mounted file system.

	   -m	     Perform a sanity check only.  Verify whether special is
		     mounted, or needs additional checking.  Refer to the
		     RETURN VALUE section for more information.





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 fsck_hfs(1M)							fsck_hfs(1M)




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

	   -p	     "Preen" the file system.  Proceed to process and repair
		     file systems without user interaction, as described
		     above.  Exit immediately if there is a problem
		     requiring intervention.

	   -P	     Same as -p except that cleanly unmounted file systems
		     are not checked.

	   -q	     Quiet.  Do not print size-check messages in Phase 1.
		     Unreferenced fifos are silently removed.  If fsck
		     requires it, counts in the superblock and cylinder
		     groups are automatically fixed.

	   -V	     Echo the completed command line, but perform no other
		     actions.  The command line is generated by
		     incorporating the user-specified options and other
		     information derived from /etc/fstab.  This option
		     allows the user to verify the command line.

	   -y|-Y     Assume a yes response to all questions asked by fsck
		     about repairing a file system.  This should be used
		     with great caution, because this is a free license to
		     continue after essentially unlimited trouble has been
		     encountered.

      In all cases, fsck checks the following inconsistencies:

	   +  Blocks claimed by more than one inode or the free list.
	   +  Blocks claimed by an inode or the free list outside the range
	      of the file system.
	   +  Incorrect link counts.
	   +  Size checks:
		   -  Directory size not of proper format.
	   +  Bad inode format.
	   +  Blocks not accounted for anywhere.
	   +  Directory checks:
		   -  File pointing to unallocated inode.
		   -  Inode number out of range.
	   +  Superblock checks:
		   -  More blocks for inodes than there are in the file
		      system.
	   +  Bad free block list format.
	   +  Total free block and/or free inode count incorrect.
	   +  Invalid continuation inode number in a primary inode.

      Orphaned files and directories (allocated but unreferenced) are, with
      the operator's concurrence, reconnected by placing them in the



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      lost+found directory.  The name assigned is the inode number.  The
      only restriction is that the directory lost+found must have empty
      slots in which entries can be made.  This is accomplished by copying a
      number of files to the directory, then removing them before fsck is
      executed.

      Unreferenced continuation inodes are removed with the -p option, since
      they do not refer back to the primary inode.  When a primary inode
      contains an invalid continuation inode number, the continuation inode
      number should be cleared (that is, set to 0).  This is not done
      automatically (with the -p option), because access control list
      information may have been lost and should be corrected.

      After fsck has checked and fixed the file system, it stores the
      correct fs_clean flag in the superblock if it is not already there.
      For a nonroot file system, FS_CLEAN is stored there.  For the root
      file system, which is mounted at the time of the fsck, no changes are
      required to the superblock if no problems were found and FS_OK was
      already set.

      Checking the raw device is almost always faster.

 RETURN VALUE
      fsck returns the following values:

	    0	Either no errors were detected or all errors were corrected.

	    1	A syntax error or other operational error occurred when
		invoked with the -V option.

	    4	Root file system errors were corrected.	 The system must be
		rebooted.

	    8	Some uncorrected errors exist on one or more of the file
		systems checked, there was a syntax error, or some other
		operational error occurred.

	   12	A signal was caught during processing.

	   32	The file system is unmounted and needs additional checking.

	   33	The file system is mounted.

	   34	The file system is damaged.

 WARNINGS
      fsck should not be run on mounted file systems or on the root device.
      If you do run on mounted file systems, be sure the system is in
      single-user state (see shutdown(1M)).





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 fsck_hfs(1M)							fsck_hfs(1M)




      The special case of the -c option, -c 0, will disable all internal
      caches, which will reduce memory usage but may impact performance.

      The -F option, from prior releases, has been replaced by the -f
      option.

 AUTHOR
      fsck was developed by HP, AT&T, the University of California,
      Berkeley.

 FILES
      /etc/fstab	    Default list of file systems to check.

      /var/adm/sbtab	    List of locations of the superblocks for file
			    systems.  The mkfs command appends entries to
			    this file.

 STANDARDS CONFORMANCE
      fsck: SVID3

 SEE ALSO
      fsck(1M), fsck_vxfs(1M), dumpfs(1M), fsclean(1M), mkfs(1M), newfs(1M),
      shutdown(1M), fstab(4), fs(4), inode(4), fs_wrapper(5), acl(5).































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