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



NAME
       fsck - file system consistency check and interactive repair

SYNOPSIS
       /etc/fsck -p [ filesystem ...  ]
       /etc/fsck [ -b block# ] [ -y ] [ -n ] [ filesystem ] ...

DESCRIPTION
       The  first  form  of  fsck  preens a standard set of filesystems or the
       specified file systems.  It is normally used in the script /etc/rc dur-
       ing  automatic reboot.  In this case fsck reads the table /etc/fstab to
       determine which file systems to check.  It uses the  information  there
       to  inspect groups of disks in parallel taking maximum advantage of i/o
       overlap to check the file systems as quickly  as  possible.   Normally,
       the  root  file system will be checked on pass 1, other ``root'' (``a''
       partition) file systems on pass 2, other small file systems on separate
       passes  (e.g.  the ``d'' file systems on pass 3 and the ``e'' file sys-
       tems on pass 4), and finally the large user file systems  on  the  last
       pass, e.g. pass 5.  A pass number of 0 in fstab causes a disk to not be
       checked; similarly partitions which are not  shown  as  to  be  mounted
       ``rw'' or ``ro'' are not checked.

       The  system takes care that only a restricted class of innocuous incon-
       sistencies can happen unless hardware or software  failures  intervene.
       These are limited to the following:

              Unreferenced inodes

              Link counts in inodes too large

              Missing blocks in the free list

              Blocks in the free list also in files

              Counts in the super-block wrong

       These  are  the only inconsistencies which fsck with the -p option will
       correct; if it encounters  other  inconsistencies,  it  exits  with  an
       abnormal  return  status  and  an automatic reboot will then fail.  For
       each corrected inconsistency one or more lines will be printed  identi-
       fying  the file system on which the correction will take place, and the
       nature of the correction.  After successfully correcting a file system,
       fsck  will print the number of files on that file system and the number
       of used and free blocks.

       Without the -p option, fsck audits and interactively repairs  inconsis-
       tent  conditions  for file systems.  If the file system is inconsistent
       the operator is prompted for  concurrence  before  each  correction  is
       attempted.   It should be noted that a number of the corrective actions
       which are not fixable under the -p option will result in some  loss  of
       data.   The amount and severity of data lost may 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 will default to a -n action.

       Fsck has more consistency checks than its predecessors  check,  dcheck,
       fcheck, and icheck combined.

       The following flags are interpreted by fsck.

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

       -y    Assume a yes response to all questions asked by fsck; this should
             be used with great caution as this is a free license to  continue
             after essentially unlimited trouble has been encountered.

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

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

       Inconsistencies checked are as follows:

       1.    Blocks claimed by more than one inode or the free list.
       2.    Blocks  claimed by an inode or the free list outside the range of
             the file system.
       3.    Incorrect link counts.
       4.    Size checks:
                   Directory size not of proper format.
       5.    Bad inode format.
       6.    Blocks not accounted for anywhere.
       7.    Directory checks:
                   File pointing to unallocated inode.
                   Inode number out of range.
       8.    Super Block checks:

                   More blocks for inodes than there are in the file system.
       9.    Bad free block list format.
       10.   Total free block and/or free inode count incorrect.

       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. The  only
       restriction  is that the directory lost+found must preexist in the root
       of the filesystem being checked and must  have  empty  slots  in  which
       entries  can be made.  This is accomplished by making lost+found, copy-
       ing a number of files to the directory, and then removing them  (before
       fsck is executed).

       Checking the raw device is almost always faster.

FILES
       /etc/fstab           contains default list of file systems to check.

DIAGNOSTICS
       The diagnostics produced by fsck are intended to be self-explanatory.

SEE ALSO
       fstab(5), fs(5), newfs(8), mkfs(8), crash(8V), reboot(8)

BUGS
       Inode  numbers  for  .  and ..  in each directory should be checked for
       validity.

       There should be some way to start a fsck -p at pass n.



4th Berkeley Distribution       4 February 1983                        FSCK(8)