




Command:   fsck, fsck1 - perform file system consistency check
Syntax:    fsck [-aclmrs] [device] ...
Flags:     -a  Automatically repair inconsistencies
           -c  Check and list only the specified i-nodes
           -l  List the files and directories in the filesytem
           -r  Prompt user for repairs if inconsistencies are found
           -s  List the superblock of the file system
Examples:  fsck /dev/hd4            # Check file system on /dev/hd4
           fsck -a /dev/at0         #  Automatically   fix   errors   on
                                      /dev/at0
           fsck -l /dev/fd0         # List the contents of /dev/fd0
           fsck -c 2 3 /dev/hd3     # Check and list /dev/hd3 i-nodes  2
                                      & 3

     Fsck performs consistency checks on the file systems  which  reside
on  the  specified  devices.   Fsck1  is an alternate version for use on
obsolete V1 file systems.  When either the -a or -r flags are given, the
file  system  will be repaired if errors are found.  Before running fsck
on a mounted file system, it must first be unmounted.  Trying to  repair
a mounted file system is dangerous and should not be attempted.

     To repair the root file system (which cannot be  unmounted),  first
hit  the F1 key to find the pid of the /etc/update process.  Then become
superuser and send update signal 9 using kill.  After doing this, hit F1
again  to  verify that /etc/update has vanished.  Next run fsck and then
immediately reboot the computer, WITHOUT doing a sync.

     This is the only situation in which you can (in fact, must)  reboot
without doing a sync.  Rebooting is needed because fsck repairs the disk
but does not affect the (possibly incorrect) information held in memory.
Doing  a  sync  would  force  the  (possibly incorrect) information from
memory back onto the disk, thus ruining  the  work  done  by  fsck.   By
rebooting  immediately, memory is reloaded with correct information from
the disk.  It is necessary to kill /etc/update before repairing the root
file system to prevent it from issuing sync calls while fsck is running.
Because /etc/update only affects mounted file systems  (and  the  root),
when repairing a nonroot file system, unmounting it is sufficient; it is
not necessary to kill /etc/update.




















                                                                        

