On 2011-03-08, Chuck Swiger <cswi...@mac.com> wrote: > Seriously, each physical machine only has one RTC and crystal > oscillator. It's useful to run one instance of ntpd in the Dom0 (or > host ESX) context where it can actually work and keep this real > hardware clock in sync.
NTP disciplines the system (i.e. kernel) clock, not the hardware clock on the mother board. > Running ntpd's in the other DomUs/guest VMs is almost entirely > pointless; it might be useful only if Dom0->DomU time is busted, > and even in that case, ntpd is unlikely to ever obtain good time > synchronization running in a DomU. That's debatable. I have a Debian 6.0 system running as a VMWare guest. ntpd on this system has no problem disciplining the clock. Recent peer billboard snapshot: steve@www:/var/log/ntpstats$ ntpq -p remote refid st t when poll reach delay offset jitter ================================================================ +ntp.my.isp .GPS. 1 u 34 1024 377 60.665 1.623 1.617 -enob... .PPS. 1 u 1041 1024 377 39.552 -8.220 2.120 *emit... .PPS. 1 u 184 1024 377 27.404 3.936 1.347 +yamo... [snip] 2 u 768 1024 377 33.565 -1.757 2.256 -3snd... [snip] 2 u 102 1024 377 26.294 7.261 1.179 Peerstats summary (last 10 days): steve@www:/var/log/ntpstats$ (cat peerstats; zcat peerstats*.gz) | wc -l 2682 steve@www:/var/log/ntpstats$ (cat peerstats; zcat peerstats*.gz) | awk -f /root/peer.awk ident cnt mean rms max delay dist disp ================================================================ [snip] 516 -1.502 1.466 6.665 38.392 960.567 24.501 [snip] 535 -7.244 1.515 8.454 41.862 962.327 23.952 [snip] 532 2.820 1.760 8.235 28.227 956.364 23.869 [snip] 521 -0.673 1.389 8.210 54.179 968.552 24.196 [snip] 534 8.565 1.741 7.829 28.114 955.486 24.080 > You are better off running ntpdate (or sntp) periodically via cron in > the DomUs. Perhaps in certain cases, but not across the board. -- Steve Kostecke <koste...@ntp.org> NTP Public Services Project - http://support.ntp.org/ _______________________________________________ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
