Leap second, NTP and HP-UX system time

[Fedon Kadifeli]

On the last day of this year (Dec 31, 2005) we are going to add a leap second. As far as I understand (see: http://www.eecis.udel.edu/~mills/leap.html ) the NTP protocol adjusts itself by setting the "NTP Leap Bit" during the last day of the year, informing the NTP clients in advance that there will be a time like "23:59:60" at the end of the day. I wonder how this is handled in HP-UX and what the effect will be on the applications.

Last time this happened in the end of year 1998. Any experiences will be appreciated.

[Jeff Schussele]

Hi Fedon,

I suspect an NTP patch will be issued - if not already out there.
Search the patch DB for NTP to see if one is available.
Short of that contact your local HP ASE for further info.

Rgds,
Jeff

[James R. Ferguson · Accepted solution]

Hi:

There is a new Technical Knowledge Base document that discusses how HP-UX's version of 'xntpd' handles the leap second. See document #KBAN00001231 released this month.

Regards!

...JRF...

[Robert-Jan Goossens_1]

Hi,

and a itrc thread with this discussion.

http://forums1.itrc.hp.com/service/forums/questionanswer.do?threadId=971488

Best regards,
Robert-Jan

[Steven E. Protter]

Shalom Fedon,

As far as I remember ntp handles it, nothing on your systems will notice it at all.

SEP

[Fedon Kadifeli]

Thanks for the quick replies. (I did a search on the forum for this topic, but it didn't return the thread you specified; thank you again for pointing me to the correct thread.)

As far as I understand, there will not be a time like 23:59:60, but instead the system time will be stepped or slewed accordingly. Similar to a case where the hardware clock runs 1 sec ahead. I am right?

[James R. Ferguson]

Hi (again) Fedon:

As far as I understand, if you or I actually watch, yes, we would see "23:59:60". The choice of how our server synchronizes to that moment -- either by a step or by a slew is dependent on the configuration we chose for 'xntpd'.

If you wish to slew time, specify :

XNTPD_ARGS=-x

in '/etc/rc.config.d/netdaemons'.

If you wish to step time changes, omit the '-x' switch. If you change the way you implement the daemon, simply stop and re-start with:

# /sbin/init.d/xntpd stop
# /sbin/init.d/xntpd start

The document reference I posted plus the man pages for 'xntpd' have additional information.

Regards!

...JRF...

[Fedon Kadifeli]

James,

Sorry for asking the same question again. But since the system will step back the time (assuming NO -x option on xntpd) 1 sec (presumably at 00:00:01 to 00:00:00) I assume there will not be a need for 23:59:60. I am missing something? Or did I misunderstand?

What I understand is something like this:

23:59:58
23:59:59
00:00:00
00:00:00 <== "leap second occurred, stepped time back 1 second"
00:00:01

[James R. Ferguson]

Hi Fedon:

The document shows examples of adding and subtracting leap seconds. Since we are apparently adding one, the document notes we will see:

23:59:58
23:59:59
23:59:60 <= leap second
00:00:00
00:00:01

Note that the adjustment occurs during the last hour of the day.

Regards!

...JRF...

[Fedon Kadifeli]

I have posted my comments to the following thread:

http://forums1.itrc.hp.com/service/forums/questionanswer.do?threadId=971488