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

NAME
       fsck - file system consistency check and	interactive repair

SYNOPSIS
       /usr/etc/fsck -p	[ -f ] [ -w ] [	-l number ] [ filesystem...  ]

       /usr/etc/fsck [ -b block# ] [ -w	] [ -y ] [ -n ]	[ -c ] [ filesystem...
       ]

DESCRIPTION
       fsck is a program that checks and repairs file system  consistency.  It
       can  operate  in	two modes, "preen" and interactive.  "Preen" is	a non-
       interactive mode	which only repairs a subset of file  system  inconsis-
       tencies.	 The interactive mode allows users to audit and	repair any in-
       consistencies.

   "Preen" Mode
       With the	-p option, fsck	audits and  automatically  repairs  ("preens")
       inconsistencies on a set	of file	systems.  If a list of file systems is
       specified on the	command	line, fsck sequentially	checks each one;  oth-
       erwise,	fsck  reads the	table /etc/fstab to determine the file systems
       to check.  It then inspects disks in parallel, taking advantage of  I/O
       overlap to check	the file systems quickly.  The number of disks checked
       in parallel can be limited using	the -l	option.	  This	helps  systems
       that  do	 not  have  sufficient memory to run enough fscks to check all
       disks in	parallel.  Preen mode is normally used in the  /etc/rc	script
       during automatic	reboot.

       Each  file  system's  super block clean flag is examined	and only those
       file systems not	marked clean or	stable are checked.  A message identi-
       fying  the name of the device and its file system's state is printed if
       the clean flag indicates	that checking is not  necessary.   If  the  -f
       (force)	option is in effect, fsck checks the file system regardless of
       the state of its	clean flag.

       Only partitions marked in /etc/fstab with a file	system type  of	 "4.2"
       and  a non-zero pass number are checked.	 If the	force option is	in ef-
       fect, file systems with pass number 1 (typically	/, /usr, and /usr/kvm)
       are  checked  one at a time.  When pass 1 completes, all	remaining file
       systems are checked, running one	process	per disk drive.	 If the	 force
       option  is not in effect	(the default case), all	file systems with non-
       zero pass numbers are checked in	as parallel a manner as	possible.

       fsck 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, automatically.  It	displays a message for
       each inconsistency corrected that identifies the	nature	of,  and  file
       system  on  which, the correction is to take place.  After successfully
       correcting a file system, fsck sets the file system's super block clean
       flag  to	 stable,  prints  the number of	files on that file system, the
       number of used and free blocks, and the percentage of fragmentation.

       If fsck encounters other	inconsistencies	that it	cannot	fix  automati-
       cally,  it  does	not change the state of	the super block	clean flag and
       exits with an abnormal return status (and the reboot fails).  A list of
       file  systems  containing such uncorrectable inconsistencies is printed
       just before fsck	exits.

       If sent a QUIT  signal  while  preening	the  file  systems  listed  in
       /etc/fstab, fsck	finishes the file system checks, then exit with	an ab-
       normal return status and	the automatic reboot fails.   This  is	useful
       when you	wish to	finish the file	system checks, but do not want the ma-
       chine to	come up	multiuser.

   Interactive Mode
       Without the -p option, fsck audits and interactively repairs  inconsis-
       tent  conditions	 on file systems.  File	systems	are checked regardless
       of the state of their clean flag.  In this case,	fsck asks for  confir-
       mation  before  attempting any corrections.  Inconsistencies other than
       those mentioned above can often result  in  some	 loss  of  data.   The
       amount  and severity of data lost can be	determined from	the diagnostic
       output.

       The default action for each correction is to wait for the  operator  to
       respond	either yes or no.  If the operator does	not have write permis-
       sion on the file	system,	fsck defaults to a -n (no corrections) action.

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

       Inconsistencies checked in order	are as follows:

	      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.
	      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.
	      o	 Clean flag state.

       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 its size is increased.

       A file system may be specified by giving	the name of the	cooked or  raw
       device  on  which it resides, or	by giving the name of its mount	point.
       If the latter is	given, fsck finds the name of the device on which  the
       file system resides by looking in /etc/fstab.

OPTIONS
       -b     Use  the block specified immediately after the flag as the super
	      block for	the file system.  Block	32 is always an	alternate  su-
	      per block.

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

       -l number
	      Limits the number	of fscks that are run  concurrently  in	 preen
	      mode.  (See -p.)

       -w     Check writable file systems only.

       -y     Assume  a	 yes  response	to  all	 questions asked by fsck; this
	      should be	used with extreme caution, as it is a free license  to
	      continue,	even after severe problems are encountered.

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

       -p     Audit and	automatically repair inconsistencies on	 file  systems
	      whose  state  is	either active or unknown.  If no other options
	      are specified, fsck inspects file	systems	listed	in  /etc/fstab
	      in  parallel,  simultaneously checking one file system per disk.
	      If file systems are specified on the command line, inspection is
	      sequential.

       -c     If  the file system is in	the old	(static	table) format, convert
	      it to the	new (dynamic table) format.  If	the file system	is  in
	      the  new	format,	 convert it to the old format provided the old
	      format can support the file system configuration.	  In  interac-
	      tive mode, fsck lists the	direction the conversion is to be made
	      and asks whether the conversion should be	done.  If  a  negative
	      answer  is given,	no further operations are done on the filesys-
	      tem.  In preen mode, the direction of the	conversion  is	listed
	      and  done	 if  possible without user interaction.	 Conversion in
	      preen mode is best used when all the file	systems	are being con-
	      verted  at  once.	 The format of a file system can be determined
	      from the first line of output from dumpfs(8)

FILES
       /etc/fstab	   default list	of file	systems	to check
       /etc/mtab	   list	of mounted file	systems

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

       2      A	QUIT signal was	caught while preening the file systems	listed
	      in /etc/fstab; abort the reboot procedure.

       4      Errors on	the root or a mounted file system 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 er-
	      ror occurred.

       12     An INTERRUPT signal was caught during processing.

DIAGNOSTICS
       The diagnostics produced	by fsck	are fully enumerated and explained  in
       the  System  and	Network	Administration Manual with the following addi-
       tions.

       1.     After checking a file system in non-preening mode, the question:
		  CLEAN	FLAG IN	SUPERBLOCK IS WRONG; FIX?
	      is asked if the file system's clean state	is wrong.  A "yes" re-
	      sponse instructs fsck to reset this state	to active if there are
	      inconsistencies, or to stable if there are no uncorrected	incon-
	      sistencies.   A "no" response instructs fsck to leave the	exist-
	      ing state	unchanged.

       2.     When fsck	is run in preen	mode, the file systems that need addi-
	      tional attention are normally scrolled off the screen.  With the
	      enhanced version of fsck these file systems listed as  fsck  ex-
	      its.  This provides the user with	a list of the the file systems
	      that require attention.  An example follows:
		      .
		      .
		      .
		  /dev/rsd6a: UNEXPECTED INCONSISTENCY;	RUN fsck MANUALLY.

		  THE FOLLOWING	FILE SYSTEMS HAD AN UNEXPECTED INCONSISTENCY:
		      /dev/rsd6a (/sd6a), /dev/rsd6b (/sd6b)
		      Reboot failed...help!

CAVEAT
       Because super block consistency checks are not made when	the -b	option
       is  used, it is recommended that	-b be augumented with the -n option to
       verify fsck actions.  Once you are satisfied that the fsck actions  are
       correct,	then remove the	-n.

SEE ALSO
       fs(5),  fstab(5),  dumpfs(8),  newfs(8),	mkfs(8), panic(8S), reboot(8),
       rexecd(8C), ypserv(8)

       System and Network Administration

				 18 June 1991			       FSCK(8)

NAME | SYNOPSIS | DESCRIPTION | OPTIONS | FILES | EXIT STATUS | DIAGNOSTICS | CAVEAT | SEE ALSO

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