# 2.11BSD#431 - /usr/man/cat8/update.0

    UPDATE(8)	    UNIX Programmer's Manual		UPDATE(8)

    NAME
         update - periodically update the super block

    SYNOPSIS
         update

    DESCRIPTION
         Update is a program that executes the sync(2) 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 ALSO
         sync(2), sync(8), init(8), rc(8)

    BUGS
         With update running, if the CPU is halted just as the sync
         is executed, a file system can be damaged.  This is par-
         tially due to DEC hardware that writes zeros when NPR
         requests fail.  A fix would be to have sync(8) 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.

    Printed 11/26/99	November 17, 1996			1

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