Re: [gentoo-amd64] Clock skew

[Richard Freeman]

On Tue, October 18, 2005 7:03 pm, Michael Kjorling wrote:
> So they say, but I'd be careful with running ntpdate from a cron job.
> I recall a recent discussion (think it was on linux@×××××××××××.com,
> but could be wrong) where one person was having real trouble because
> of it resetting the system clock. When he converted to running ntpd
> instead, the problem disappeared.
>

Hmm, my guess (somewhat educated) is that ntpdate is abruptly changing the
clock, while ntpd normally just slews the clock by adjusting the timer
settings.  This means that every second on the clock still ticks with
ntpd, but not with ntpdate.  That probably has a big impact on anything
that uses real-time-clock scheduling - especially if you're running
ntpdate once a minute or something like that.

I'm not sure how multimedia works in linux - it may not use the system
clock for timing.  If it did I could definintely see issues happening if
buffers run out or if video/audio get out of sync.

I personally just let leave the RTC on GMT and run ntpd.  It is mostly
fire-and-forget.  As others have pointed out though, it doesn't handle
clock slews this large easily (maybe there is a parameter or
source-code-constant that can be tweaked to compensate).
-- 
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