UPDATE(VIII) 11/1/73 UPDATE(VIII)





UPDATE(VIII)                 11/1/73                 UPDATE(VIII)







NAME

     update - periodically update the super block



SYNOPSIS

     update



DESCRIPTION

     Update is a program that executes the sync  primitive  every

     30  seconds.  This insures that the file system is fairly up

     to date in case of a crash.   This  command  should  not  be

     executed  directly,  but  should  be  executed  out  of  the

     initialization  shell  command  file.   See  sync  (II)  for

     details.



SEE ALSO

     sync (II), init (VIII)



BUGS

     With update running, if the CPU is halted just as  the  sync

     is  executed,  a  file  system  can  be  damaged.   This  is

     partially due to DEC hardware that  writes  zeros  when  NPR

     requests  fail.   A  fix  would  be to have sync temporarily

     increment the system time by at least 30 seconds to  trigger

     the  execution  of update.  This would give 30 seconds grace

     to halt the CPU.
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