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NAME    [Toc]    [Back]

       fsck, ufs_fsck - Check and repair UFS file systems

SYNOPSIS    [Toc]    [Back]

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

OPTIONS    [Toc]    [Back]

       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  format,
       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 command.
       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 specified
  in octal as the permission bits to use when creating
       the lost+found directory rather than the default  777.  In
       particular,  systems  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.
       Noninteractively corrects 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, 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

DESCRIPTION    [Toc]    [Back]

       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

       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 command checks the file systems in the /etc/fstab

       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
       specify  the  -f  option.  Use  this  option with caution,
       because it can cause the data on the running  system  (the
       in-memory  data)  to  become  unsynchronized from the file
       system data (the on-disk data).

       The fsck program interactively repairs  inconsistent  file
       system conditions.  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 number 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  inconsistencies  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 diagnostic 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  nonzero
  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 nonzero
 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.

ERRORS    [Toc]    [Back]

       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

EXAMPLES    [Toc]    [Back]

       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

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

FILES    [Toc]    [Back]

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

SEE ALSO    [Toc]    [Back]

       Commands: newfs(8)

[ Back ]
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