[Discuss] Issuing the 'sync' command more than once (and a tangent on how not to run a high-tech company)

[gaf at blu.org (Jerry Feldman)]

On 06/16/2012 08:54 PM, Richard Pieri wrote:
> On 6/16/2012 3:34 PM, MBR wrote:
>> Even though the OS guys knew that typing 'sync', waiting about 5
>> seconds, then typing 'halt' was really all that was necessary, most of
>> the programmers writing application level code didn't know that.
>
> As Jerry noted, some early Unixes had issues.  Invoking halt after
> sync is a race condition regardless of how many sync invocations are
> used. Three invocations of sync -- "sync;sync;sync;halt" as a single
> shell command -- was considered sufficient for nearly every occasion. 
> The exceptions could then be relegated to incompetent users waiting
> until literally the last milliseconds to save their work or act of
> $DEITY, take your pick.
>
I don't think it caused a race condition in older system V (Cadmus where
I worked), or on BSD. At Digital we generally used the shutdown(8) command.

-- 
Jerry Feldman <gaf at blu.org>
Boston Linux and Unix
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