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.