I have noticed that when I start ntpd on a server, checks against that server reveal that it has a stratum of zero. If I understand this correctly, I believe this means that ntpd is currently only using itself as the time source.

After a minute or so, it checks against the server, and the stratum is no longer zero.

Do I understand this correctly, and can I speed up time the time before it becomes non-zero?

  • In your ntp configuration, there should be a "local clock" reference. What is the stratum listed there? – Matt Simmons May 6 '11 at 13:12
  • That isn't in the ubuntu server default configs. – Kyle Brandt May 6 '11 at 13:17
  • Interesting. The CentOS/RHEL config has two servers configured with "server 127.1271.0 stratum 10". Looking at that again, I'm pretty sure it doesn't change the behavior you're talking about. – Matt Simmons May 6 '11 at 13:27
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    OK, mine defaults to stratum 16 when it's in the initial startup. What ntp server are you running? – Matt Simmons May 6 '11 at 13:38
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    Guys, clearly the part that Kyle left out is that he's got his server hooked up to a TARDIS. – Phil Hollenback May 6 '11 at 15:22

This sounds like a bug (or a configuration edit gone horribly wrong) - As Matt Simmons pointed out ntpd usually defaults to Stratum 16 ("Unsynchronized").

My (admittedly limited) understanding of NTP strata is that Stratum 0 is reserved for reference clocks (a cesium clock for example, or a GPS Time receiver) that you would attach to a computer to create a stratum 1 server (using the stratum 0 device as its reference).

  • Hmm... could be the Nagios check_ntp_time gone wrong as well.... – Kyle Brandt May 6 '11 at 15:31
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    Could be - I'm not sure how good the Nagios NTP stuff is. What does ntpq -c readlist show as the stratum? – voretaq7 May 6 '11 at 15:38
  • @vortaq7: It shows 16, so apparently it is this program being silly. – Kyle Brandt May 6 '11 at 20:28

Local clock should not be used.

you can speed up synchronization by using the iburst keyword for your server definitions.

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