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fsck(8)								       fsck(8)

       fsck, ufs_fsck - Check and repair UFS file systems

       /usr/sbin/fsck [fs_options] [filesystem...]

       The following options are interpreted by fsck: Uses the specified block
       number as the super block for the file system. Block 32 is  usually  an
       alternate  super	 block.	 Converts UFS Version 4 back to UFS Version 3.
       When you use the -B option on a UFS Version 4 file system, it  will  be
       marked  as a Version 3 file system if there are no files or directories
       with more than 32767 hardlinks or 32765 subdirectories.	 If  the  file
       system  is in the old (static table) format, this option converts it to
       the new (dynamic table) format. If the file system is in the  new  for‐
       mat,  this  option converts it to the old format, provided that the old
       format can support the file system configuration.  In interactive mode,
       fsck  lists  the direction of the conversion and asks if the conversion
       should be done. If you answer "no," no further operations are  done  on
       the  file  system.  If the -p option is specified, the direction of the
       conversion is listed and	 the  conversion  is  performed	 without  user
       interaction  if	possible. The -p option should be used if all the file
       systems are being converted simultaneously. The format of a file system
       can  be	determined  from the first line of output from the dumpfs com‐
       mand.  Forces fsck to check the root file system, even  when  the  file
       system  is  mounted  as writable. Use this option with caution, because
       running fsck on a mounted root file  system  can	 cause	its  files  to
       become out of synchronization with running system data.	If the problem
       occurs, the fsck program displays a message recommending you reboot the
       system.	 Limits the number of parallel checks to the number specified.
       By default, the limit is the number of disks running  one  process  per
       disk.  If a smaller limit is given, the disks are checked using a round
       robin-type schedule, one file system at a time.	Uses the  mode	speci‐
       fied  in	 octal	as  the	 permission  bits  to  use  when  creating the
       lost+found directory rather than the default 777. In  particular,  sys‐
       tems that do not want to have lost files accessible by all users on the
       system should use a more restrictive set of permissions, such  as  700.
       Answers	"no" to all the prompts except for the “CONTINUE?” prompt. The
       option does not write to the lost+found file in the  file  system.   If
       you  do	not have write permission on the file system, fsck defaults to
       the behavior of the -n option.  Causes fsck  to	unconditionally	 check
       the  file system even if the file system's clean byte is set.  That is,
       a file system is checked even if it has been unmounted cleanly.	Nonin‐
       teractively  corrects the following file system inconsistencies: unref‐
       erenced inodes, link counts in  inodes  that  are  too  large,  missing
       blocks  in the free map, blocks in the free map that are also in files,
       and wrong counts in the super-block.  Causes more extensive messages to
       be  displayed  during  the  file system checks (verbose mode).  Answers
       "yes" to all the prompts. This  option  should  be  used	 with  caution
       because	the  integrity	of  the	 file  system data can be corrupted by
       answering "yes" to all the prompts.

       The fsck command is a front-end program for the ufs_fsck program, which
       checks  and repairs UFS file systems. Do not use this command for AdvFS
       file systems:  instead, see advfs(4).

       The fsck program has more consistency checks than  its  check,  dcheck,
       fcheck, and icheck predecessors combined.

       You must be root to use this command.

       If  you do not specify a file system in the command line, the fsck com‐
       mand checks the file systems in the /etc/fstab file.

       With one exception, the fsck command cannot be used on an  active  file
       system.	The  command  checks  to determine whether the partition to be
       checked, or an overlapping partition, is in use.	 The exceptional  case
       occurs when you run the command on an active root file system and spec‐
       ify the -f option. Use this option with caution, because it  can	 cause
       the  data  on  the running system (the in-memory data) to become unsyn‐
       chronized from the file system data (the on-disk data).

       The fsck program interactively repairs inconsistent file system	condi‐
       tions.	If  the	 file  system is found to be consistent, the number of
       files, blocks used, and free blocks are reported.  If the  file	system
       is  inconsistent, you are prompted before each correction is attempted.
       For each corrected inconsistency, one  or  more	lines  are  displayed,
       identifying the file system on which the correction takes place and the
       type of correction.  After successfully correcting a file  system,  the
       fsck program displays the number of files on that file system, the num‐
       ber of used and free blocks, and the percentage of fragmentation.

       The default behavior of the fsck program is to interactively check  the
       following UFS file system inconsistencies:

       Blocks claimed by more than one inode or the free map
       Blocks claimed by an inode outside the range of the file system
       Incorrect link counts
       Size checks: directory size not of proper format; partially truncated file
       Bad inode format
       Blocks not accounted for anywhere
       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
       Super Block checks: more blocks for inodes than there are in the file system
       Bad free block map format
       Total free block and/or free inode count incorrect

       If you use the -p option, the fsck program noninteractively attempts to
       correct specific file system inconsistencies.  The corrections are made
       only  if they can be done safely. The fsck program can noninteractively
       correct the following file system inconsistencies:

       Unreferenced inodes
       Link counts in inodes that are too large
       Missing blocks in the free map
       Blocks in the free map that are also in files
       Wrong counts in the super-block.

       If fsck encounters any other inconsistencies, it exits with an abnormal
       return status and a subsequent reboot will fail.

       The  system makes sure that only a restricted class of innocuous incon‐
       sistencies can occur unless hardware or software failures intervene.

       Note that some of the corrective actions can result in a loss of	 data.
       The  amount  and severity of data lost can be determined from the diag‐
       nostic output.

       At system boot, fsck -p runs automatically  and	reads  the  /etc/fstab
       file to determine which file systems to check. Only partitions that are
       mounted rw or ro and have a  non-zero  pass  (1	or  more)  number  are
       checked.	 File systems that have a pass number 1 (usually only the root
       file system) are checked one at a time.	When  pass  1  completes,  the
       remaining  pass	numbers	 are  processed with one parallel fsck process
       running per disk drive in the same pass.

       The per disk drive logic is based on the /dev/disk/dsk0a	 syntax	 where
       different  partition  letters  are  treated  as	being on the same disk
       drive.  Partitions layered on top of an LSM device may not follow  this
       naming  convention.  Where LSM is used, you can use unique pass numbers
       in the /etc/fstab file to sequence the fsck checks.

       If a QUIT signal is sent, fsck finishes the file system checks and then
       exits  with  an abnormal return status that causes the automatic reboot
       to fail. This is useful if you want to finish the  file	system	checks
       during  an  automatic  reboot  but  do  not want the machine to come up
       multiuser after the checks complete.

       If the fsck default program fails (terminates with a  non-zero  value),
       fsck terminates with the exit value.  This ensures that the auto-reboot
       dependencies, such as those commonly used in the	 run  command  script,
       continue to function.

       If  orphaned  files  or	directories  (allocated	 but unreferenced) are
       found, you are asked if you want to reconnect the files and directories
       that  are  not  empty by putting them in the lost+found directory.  The
       program indicates whether the file or directory is empty or not	empty.
       The  fsck program reconnects directories that are not empty and assigns
       the inode number for the name.  If the lost+found  directory  does  not
       exist,  it  is  created,	 and if it has insufficient space, the size is
       increased. Empty files and directories are removed unless  you  specify
       the -n option.

       The following message indicates that the system is avoiding a potential
       panic by skipping the  file  system  check:  /dev/disk/dsk2g:  skipping
       filesystem already mounted (read-write) on '/usr'

       The  following  message	indicates  that	 the  file  system is mounted:
       /dev/disk/dsk2g on /usr: Device busy

       The following message indicates that the partition you are checking  is
       open:  ERROR: /dev/rdisk/dsk3a or an overlapping partition is open fsck
       cannot be run on an active filesystem

       The following is an example of an /etc/fstab file that is used  in  the
       examples in this section:

       /dev/disk/dsk2a	   /	       ufs rw 1 1 /dev/disk/dsk0g     /usr ufs
       rw  1  2	 /dev/disk/dsk2b      swap1	ufs  sw	 0  2  /dev/disk/dsk0b
       /public	 ufs   sw   0	2   /dev/disk/dsk2g	  /var ufs   rw	  1  2
       /dev/disk/dsk3c	   /usr/users ufs rw 1 2

       The following command checks all the file  systems  in  the  /etc/fstab
       file but makes no corrections: # fsck -n

       The following example checks a file system found in the /etc/fstab file
       and checks a file system that is not found in the  /etc/fstab  file:  #
       fsck  /dev/rdisk/dsk3c  /dev/rdisk/dsk1a

       The  following  command noninteractively checks the file systems in the
       /etc/fstab file: # fsck -p

       Specifies the command path.  Specifies the command path.	 Contains  the
       default list of file systems to check.

       Commands: newfs(8)


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