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Command: update | Section: 8 | Source: UNIX v7 | File: update.8
UPDATE(8) System Manager's Manual UPDATE(8)
NAME
update - periodically update the super block
SYNOPSIS
/etc/update
DESCRIPTION
Update is a program that executes the sync(2) primitive every 30 sec-
onds. 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(1), init(8)
BUGS
With update running, if the CPU is halted just as the sync is executed,
a file system could be damaged. (This used to be the case with DEC
hardware that wrote zeros when NPR requests failed.) A fix would be to
have sync(1) temporarily increment the system time by at least 30 sec-
onds to trigger the execution of update. This would give 30 seconds
grace to halt the CPU.
UPDATE(8)