FSCK(8)                                                   FSCK(8)

     NAME
          fsck - file system consistency check and interactive repair

     SYNOPSIS
          /etc/fsck -p [ filesystem ...  ]
          /etc/fsck [ -y ] [ -n ] [ -sX ] [ -SX ] [ -t filename ] [
          filesystem ] ...

     DESCRIPTION
          The first form of fsck preens a standard set of filesystems
          (those mentioned in /etc/fstab) or the specified file sys-
          tems.  It is normally called from /etc/rc during automatic
          reboot.

          The file /etc/fstab defines the order in which disks are
          checked by assigning each file system to a ``pass'' of fsck.
          Normally, the root file system will be checked on pass 1,
          and other files on later passes.  For savecore(8) to work,
          no more than three large file systems should be checked on
          each pass.  A file system is not checked if its pass number
          is 0 or it is not to be mounted.

          Fsck with the -p option will repair only the following ail-
          ments:

               unreferenced i-nodes;

               wrong link counts in i-nodes;

               missing blocks in the free list;

               blocks in the free list also in files; and

               counts wrong in the super-block.

          If fsck encounters other inconsistencies, it exits with an
          abnormal return status and the automatic reboot aborts.  For
          each corrected inconsistency one or more lines will be
          printed identifying the file system and the nature of the
          correction.  After successfully preening 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
          inconsistent conditions on file systems. If the file system
          is inconsistent the operator is prompted for concurrence
          before each correction is attempted.  The operator may
          require arcane knowledge to guide fsck safely through repair
          of a badly damaged file system.

     FSCK(8)                                                   FSCK(8)

          The following flags are interpreted by fsck.

          -y    Assume a yes response to all questions asked by fsck;
                this should be used with great caution.

          -n    Assume a no response to all questions asked by fsck;
                do not open the file system for writing.  This option
                is enabled automatically if the file system is not
                writable.

          -sX   Ignore the actual free list and (unconditionally)
                reconstruct a new one by rewriting the super-block of
                the file system. The file system should be unmounted
                while this is done; if this is not possible, care
                should be taken that the system is quiescent and that
                it is rebooted immediately afterwards.  This precau-
                tion is necessary so that the old, bad, in-core copy
                of the superblock will not continue to be used, or
                written on the file system.  If the file system has a
                bitmap free list (see filsys(5)), the free list is
                always reconstructed unless the -n option is enabled.

                The -sX option allows for creating an optimal free-
                list organization.  The following forms of X are sup-
                ported for the following devices:

                     -s3 (RP03)
                     -s4 (RP04, RP05, RP06)
                     -sBlocks-per-cylinder:Blocks-to-skip (for anything else)

                If X is not given, the values used when the filesystem
                was created are used.  If these values were not speci-
                fied, then the value 400:9 is used.

          -SX   Conditionally reconstruct the free list. This option
                is like -sX above except that the free list is rebuilt
                only if there were no discrepancies discovered in the
                file system. The -S option enables -n.

          -t    If fsck cannot obtain enough memory to keep its
                tables, it uses a scratch file. If the -t option is
                specified, the file named in the next argument is used
                as the scratch file, if needed. Without the -t flag,
                fsck will prompt the operator for the name of the
                scratch file. The file chosen should not be on the
                filesystem being checked, and if it is not a special
                file or did not already exist, it is removed when fsck
                completes.

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

     FSCK(8)                                                   FSCK(8)

          Inconsistencies checked are as follows:

          Blocks claimed by more than one inode or the free list.
     the file system.
          Blocks claimed by an inode or the free list outside the range of
          Incorrect link counts.
          Size checks:
          Directory size not 16-byte aligned.
          Bad inode format.
          Blocks not accounted for anywhere.
          Directory checks:
          File pointing to unallocated inode.
               Inode number out of range.
          Super Block checks:
          More than 65536 inodes.
               More blocks for inodes than there are in the file sys-
               tem.
          Bad free block list format.
          Total free block and/or free inode count incorrect.

          Orphaned files and directories (allocated but unreferenced)
          are 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 exist in the root of
          the filesystem being checked and must have empty slots in
          which entries can be made.

          Checking the raw device is almost always faster for 1K-block
          file systems, but bitmap file systems must be checked using
          the block device.

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

     SEE ALSO
          fstab(5), filsys(5), crash(8), reboot(8)

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

          The `three large filesystems' rule assumes a system with 4
          megabytes of memory and a 20 megabyte swap area.  Your
          mileage may vary.  The goal is to avoid overwriting the part
          of the swap area where the dump lives.