On 2011-12-10, Harlan Stenn <[email protected]> wrote: > Steve wrote: > >> Bruce wrote: >> >> > Those times apply *after* enough samples have been gathered for >> > an offset estimate, which happens *after* a system peer has been >> > selected. That can take many minutes. With ntp-wait, the boot >> > sequence would be effectively stalled for the duration. >> >> There is no need to use ntp-wait. >> >> Use sntp. >> >> Use a separate 'ntpd -gq' invocation. > > Why?
Because the current practice of using ntpdate to initially set the clock is GoodEnough(tm) for most users; and both sntp and 'ntpq -gq' are, for the most part, the functional equivalent of ntpdate. > ntp-wait will block until leap != 11, which means that ntpd is > satisfied that it has a sufficient understanding of time sync that > steps should not be needed and timekeeping is on its way to stability. > > ntp-wait can be used to wait until this is true, at which time it is > considered safe to start things like database servers and dovecot. > > If you are not running any of these sort of services there is no need > to run ntp-wait. It may be interesting to find out how many people currently use ntp-wait. >> > 2. your estimate of "fully sync'd in 11 seconds' time" seemed >> > overly optimistic (and still does, even with minimum polling times and >> > maximum slew rate). >> >> The 11 second figure applies to the initial setting of the clock with >> 'ntpd -gq' (which is analogous to the use of ntpdate for the same >> purpose) and not to disciplining the clock to maximum stability. > > I'm not gonna dig deeply into that one, but I will say that I remember > seeing similar values for "delay" when using ntp-wait. The 11 second figure for 'ntpd -gq' came from warm-restart tests I ran on my previous home LAN under optimal conditions (local DNS and a LAN time server). -- Steve Kostecke <[email protected]> NTP Public Services Project - http://support.ntp.org/ _______________________________________________ questions mailing list [email protected] http://lists.ntp.org/listinfo/questions
