On Fri, Jun 19, 2015 at 06:29:34PM +0000, Mel Beckman wrote:
The universal workaround is to simply disable NTP on your devices sometime on Leap-Second eave. This will let the clocks free-run over the one-second push, an event of which they will be blissfully ignorant. When you re-enable NTP after The Leap, normal, non-destructive, NTP convergence will occur.
<randy>I encourage all my competitors to use this approach.</randy> If you're more than 128 ms off when NTP is flipped back on, it will still probably step the clock, then start slewing it. So you've skipped the leap per se, but your clocks will still jump forward quite a bit. This might isolate you from any leap second related failures, but it does not protect you against the system clock being stepped. If the leap pending information data persists, you might not even be isolated from any leap second failures. You could manage to upset the system clock even more. Are your time servers correctly armed for the leap?
Better, if you have a master NTP site clock, you need only disable it’s upstream NTP feed to isolate all the subsidiary devices. If you don’t have such a master clock, this is an excellent time to set one up one. I have found the Time Machines TM1000A GPS time server very inexpensive and super reliable:
http://www.newegg.com/Product/Product.aspx?Item=0N6-001Y-00007
$20 says that doesn't leap correctly. A lot of the inexpensive units appear to be using NMEA speaking GPS modules, and there's no real way to get leap information out of them. Many of them may ignore the timestamps and just use the PPS, in which case they may persist a second behind the world for quite some time. --msa