On Fri, 2011-07-15 at 18:05 +0200, Per Jessen wrote:
Roger Oberholtzer wrote:
On Fri, 2011-07-15 at 17:04 +0200, Per Jessen wrote:
Roger Oberholtzer wrote:
I may not have understood all of your problem, but without a frequent connection to an accurate time-source, any system will have to rely on a local clock for periods of time. AFAICT, both chrony and ntp know how to determine the local oscillator drift and massage the clock such that the local clock remains fairly accurate. If you need a higher degree of accuracy without a more accurate external time source, you have to improve the local time source - temperature controlled xtal oscillator etc.
This massaging does seem to happen when ntp is running and after it has a server. But I am not convinced that anything is done when ntp starts and before it gets in contact with a server.
If properly configured ntp will _always_ have a server - the local clock. The drift of the local clock oscillator will have been determined, so ntp will use that to keep massaging the clock until a better source becomes available.
But the localclock, when ntp is used, is from the BIOS, which is UTC, which is incorrect.
And that is what chrony provides. A useful estimate of time before the first server is found.
I don't know anything about chrony, so I have to wonder what information it has that ntp does not?
It is not so much that it has different information. In fact, in many ways it is like ntp. The difference is subtle. Whereas ntp does not seem to retry non-existent servers (real 'not localhost'), chrony does. Obviously, until chrony gets a hold of an external server, the time will not be in sync. In the case of GPS receivers, chrony takes great advantage of the new PPS driver. When the GPS starts sending data, chrony detects this immediately and gets the time correct. -- Roger Oberholtzer OPQ Systems / Ramböll RST Ramböll Sverige AB Krukmakargatan 21 P.O. Box 17009 SE-104 62 Stockholm, Sweden Office: Int +46 10-615 60 20 Mobile: Int +46 70-815 1696 SHAW'S PRINCIPAL Build a system that even a fool can use, and only a fool will want to use it. -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org For additional commands, e-mail: opensuse+help@opensuse.org