AST RESEARCH, INC.         TECHNICAL BULLETIN #0874               10-11-93




             CO UNIX fsck(ADM) COMMAND AND AST COMPUTER SYSTEMS


PROBLEM:       The message "FREE BLK COUNT WRONG IN SUPERBLK" is encountered
               when executing the fsck command on the root filesystem.
               
SYSTEMS
AFFECTED:      All AST computer systems using SCO UNIX or SCO ODT operating
               systems.

CAUSE:         The root filesystem is mounted when the fsck command is
               executed.

SOLUTION:      Boot from the Emergency Boot Floppy set and execute fsck on
               the root filesystem.  (Reference SCO's Installation Guide for
               more information regarding creating an Emergency Boot Floppy
               set)

               If the floppy set isn't available, customers have reported
               that synching the cache and disk filesystem structures three
               times immediately prior to executing fsck often results in
               fsck executing without errors.  For example:

               1.   Enter single-user mode
               2.   sync;sync;sync;fsck -b /dev/root

NOTE:  Erroneous errors can be reported any time fsck is executed on a
       mounted filesystem, including incorrect free block count, incorrect
       free inode count, lost inodes, etc.  This is because the UNIX
       filesystem keeps in-memory caches of filesystem structures, but fsck
       reads the filesystem directly from the disk.  It is normal for the in-
       memory and on-disk filesystem structures to be slightly out of sync.