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

NAME
       fsck -- file system consistency check and interactive repair

SYNOPSIS
       fsck  [-Cdfnpvy]	[-B | -F] [-T fstype:fsoptions]	[-t fstype] [-c	fstab]
	    [special | node] ...

DESCRIPTION
       The fsck	utility	invokes	file system-specific  programs	to  check  the
       special	devices	listed in the fstab(5) file or in the command line for
       consistency.

       It is normally used in the  script  /etc/rc  during  automatic  reboot.
       Traditionally,  fsck is invoked before the file systems are mounted and
       all checks are done to completion at that time.	If background checking
       is available, fsck is invoked twice.  It	is first invoked at the	tradi-
       tional time, before the file systems are	mounted, with the -F  flag  to
       do checking on all the file systems that	cannot do background checking.
       It  is then invoked a second time, after	the system has completed going
       multiuser, with the -B flag to do checking on all the file systems that
       can do background checking.  Unlike the foreground checking, the	 back-
       ground checking is started asynchronously so that other system activity
       can proceed even	on the file systems that are being checked.

       If  no  file  systems are specified, fsck reads the table /etc/fstab to
       determine which file systems to check.  Only partitions	in  /etc/fstab
       that  are mounted "rw", "rq" or "ro" and	that have non-zero pass	number
       are checked.  File systems with pass number 1 (normally just  the  root
       file system) are	always checked one at a	time.

       If not in preen mode, the remaining entries are checked in order	of in-
       creasing	 pass  number  one at a	time.  This is needed when interaction
       with fsck is required.

       In preen	mode, after pass 1 completes, all remaining file  systems  are
       checked,	 in  pass  number  order running one process per disk drive in
       parallel	for each pass number in	increasing order.

       In other	words: In preen	mode all pass 1	partitions are checked sequen-
       tially.	Next all pass  2  partitions  are  checked  in	parallel,  one
       process per disk	drive.	Next all pass 3	partitions are checked in par-
       allel, one process per disk drive.  etc.

       The  disk drive containing each file system is inferred from the	short-
       est prefix of the device	name that ends in a digit; the remaining char-
       acters are assumed to be	the partition and slice	designators.

       If the -t or -T flags are not specified,	fsck will attempt to determine
       the file	system type and	call the appropriate file system  check	 util-
       ity.   Failure  to  detect the file system type will cause fsck to fail
       with a message that the partition has an	unknown	file system type.

       The options are as follows:

       -C      Check if	the "clean" flag is set	in  the	 superblock  and  skip
	       file  system  checks if file system was properly	dismounted and
	       marked clean.

       -c fstab
	       Specify the fstab file to use.

       -d      Debugging mode.	Just  print  the  commands  without  executing
	       them.  Available	only if	fsck is	compiled to support it.

       -f      Force  checking of file systems.	 Running "fsck -f" ignores the
	       journal and does	a full consistency check of the	disk  so  will
	       find and	fix the	errors about which the journal is unaware.

       -n      Causes  fsck  to	 assume	no as the answer to all	operator ques-
	       tions, except "CONTINUE?".

       -p      Enter preen mode.  In preen mode, only a	 restricted  class  of
	       innocuous  file	system	inconsistencies	will be	corrected.  If
	       unexpected inconsistencies caused by hardware or	software fail-
	       ures are	encountered, the check program will exit with a	 fail-
	       ure.   See  the	manual pages for the individual	check programs
	       for a list of the sorts of failures that	they correct when run-
	       ning in preen mode.

       -F      Run in foreground mode.	The check program for each file	system
	       is invoked with the -F flag to determine	whether	it  wishes  to
	       run as part of the boot up sequence, or if it is	able to	do its
	       job  in	background after the system is up and running.	A non-
	       zero exit code indicates	that it	wants to run in	foreground and
	       the check program is invoked.  A	zero exit code indicates  that
	       it  is able to run later	in background and just a deferred mes-
	       sage is printed.

       -B      Run in background mode.	The check program for each file	system
	       is invoked with the -F flag to determine	whether	it  wishes  to
	       run as part of the boot up sequence, or if it is	able to	do its
	       job  in	background after the system is up and running.	A non-
	       zero exit code indicates	that it	wanted to  run	in  foreground
	       which  is  assumed  to  have  been  done, so the	file system is
	       skipped.	 A zero	exit code indicates that it is able to run  in
	       background  so the check	program	is invoked with	the -B flag to
	       indicate	that a check on	the active file	system should be done.
	       When running in background mode,	only one file system at	a time
	       will be checked.	 Note  that  background	 fsck  is  limited  to
	       checking	 for  only the most commonly occurring file system ab-
	       normalities.  Under certain circumstances, some errors can  es-
	       cape background fsck.  It is recommended	that you perform fore-
	       ground  fsck  on	your systems periodically and whenever you en-
	       counter file-system-related panics.

       -t fstype
	       Invoke fsck only	for the	comma separated	list  of  file	system
	       types.	If  the	list starts with "no" then invoke fsck for the
	       file system types that are not specified	in the list.

       -v      Print the commands before executing them.

       -y      Causes fsck to assume yes as the	answer to all  operator	 ques-
	       tions.

       -T fstype:fsoptions
	       List  of	 comma	separated file system specific options for the
	       specified file system type, in the same format as mount(8).

FILES
       /etc/fstab  file	system table

SEE ALSO
       fstab(5), fsck_ffs(8), fsck_msdosfs(8), mount(8)

HISTORY
       A fsck utility appeared in 4.0BSD.  It was reimplemented	as a  filesys-
       tem   independent   wrapper   in	 NetBSD	 1.3  and  first  appeared  in
       FreeBSD	5.0.   The  original  filesystem   specific   utility	became
       fsck_ffs(8) at this point.

FreeBSD	13.2			 March 5, 2019			       FSCK(8)

NAME | SYNOPSIS | DESCRIPTION | FILES | SEE ALSO | HISTORY

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