[ntp:questions] Re: simple time server
bryanh at giraffe-data.com
Thu Aug 3 15:47:24 UTC 2006
>If you are willing to settle for time to the nearest second you can use
>rdate. If you need better; e.g. time to the nearest 100 milliseconds or
>better, SNTP *might* do it for you but I wouldn't want to rely on it myself.
SNTP looks, from reading the introduction in the spec, like what I
want because it's provides rdate-like service, but using essentially
NTP (which I like because it's so common) and subsecond precision.
But I would still need an SNTP server program unlike what's available
today, whereas an adequate rdate ("time" protocol) server already
exists. So I'll have to weigh my options -- thanks for providing
>You can, if you wish, use ntpdate to set your clocks from some NTP
>server. You could run it in a cron job once an hour or something like
>that and it should keep your clock within a hundred milliseconds of the
>server unless you have a machine with a really bad local clock.
For my computers on the Internet, I have been doing something like
this, but much less, for many years and have been quite happy with it.
My cron job runs Ntpdate once a _week_ and I monitor the amount of
correction it has to make. When the system clock is properly
calibrated, it's about 50 milliseconds each week. On a few of the
computers, the clock speed changes so that a couple of times a year
the correction grows beyond 250 milliseconds, and I manually change
the clock speed (Linux adjtimex) to get back to the 50 ms/week. Note
that for corrections less than 500 ms, Ntpdate slews the correction
For what these computers do, this is more than enough precision and I
appreciate the simplicity and flexibility of it compared to the
conventional NTP deployment (simplicity and flexibility usually mean
less maintenance work for me and fewer disasters).
[By contrast, what I'm asking about now has to do with the computers
that are not on the Internet; it would be nice if I could use the
exact same strategy on them, except point them to a simple NTP server
(on one of my computers) that serves the local system clock time.]
>Ntpdate does not provide the full functionality of ntpd and it is
>"deprecated" and sooner or later will be dropped from the
Not a problem, since I already have my copy, and the program probably
won't need any maintenance.
Bryan Henderson Phone 408-621-2000
San Jose, California
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