On Sat, Jun 30, 2012 at 03:58 UTC, Hal Murray wrote: > Many data base systems freak out if time goes backwards. I assume they are > setup to pass the slew-only flag to ntpd. I think that will take a bit over > 1/2 hour to catch up a second. It probably depends upon the normal drift of > the system.
To be pedantic, there isn't really a slew-only knob. There is always some threshold above which offset ntpd will step the clock. The long name for ntpd's -x command-line option, --no-slew, misleads, as it changes the threshold from 0.128s to 600s, not infinity. With that it mind, it should come as no surprise to you that --no-slew doesn't change leap insertion from a step into a slew. It does disable the use of the kernel discipline, which means modern ntpd implements the leap insertion by stepping back one second. With a sufficiently old ntpd, I think 4.2.4 and earlier, ntpd does not step the clock with the kernel discipline disabled -- it would eventually believe the 1s offset and start to run the clock at -500 PPM until the offset was slewed away. Cheers, Dave Hart _______________________________________________ pool mailing list [email protected] http://lists.ntp.org/listinfo/pool
