ntpdate's behavior when DNS returns multiple values
Hi All,
I have recently purchased a computer with edgy eft preinstalled. The behavior of ntpdate on it is different from what I am used to and I was wondering if anybody can explain. For example, suppose I enter: Code:
ntpdate -q 0.us.pool.ntp.org 1.us.pool.ntp.org 2.us.pool.ntp.org Has ntpdate's behavior been changed recently, has Ubuntu modified it, or what? I can't find any option listed in the man page to revert to the old behavior. Can somebody tell me what's going on? Thanks for any replies. |
I'm not sure if I can actually answer your question, but when I use ntpdate (usually in VMs these days) I just use 'ntpdate pool.ntp.org' and it just works.
The 'pool' server it responsible for picking a random ntp host to sync with. |
Oh, it "works" all right. After polling 12 NTP servers!!! (Using your command.) That is not the behavior I expect or what I have seen before. And while polling 3 servers seems perfectly reasonable to me, polling ten or more seems abusive of the good people who are kind enough to run the servers in the pool. I am just trying to get to the bottom of this. Maybe I need to file a bug report somewhere.
Thanks for your response. I'll flesh out my test below. Giving the command on the Ubuntu system: Code:
root@ubuntu:~# ntpdate pool.ntp.org Monitoring with tcpdump on the gateway computer (The long listing is greatly truncate here -- analysis of the complete file below): Code:
[root@Acer root]# tcpdump -nni eth1 udp port 123 Analyze complete output for the IP addresses which responded: Code:
<03:15:53(jim)jim>$cat /tmp/ntpdate_dump | sed -n "s/^.* \([[:digit:].]*\).123 > 192.*$/\1/p" | sort | uniq -c |
I agree that seems to be odd behaviour and not something I've seen before. Anything interesting in your /etc/ntpd.conf (or ntpdate.conf or whatever it's called)?
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Code:
user@ubuntu:~$ cat /etc/default/ntpdate |
Should there be two NTPSERVERS lines? That doesn't seem right, although I'm not sure if that would cause the behaviour your seeing.
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I was hoping somebody on the Ubuntu project might respond on this thread, as this is a real head scratcher. I though each of the forums for specific distros had some people from the respective projects monitoring them. Anyway, thanks for your replies. I'll be happy to answer any other questions or try any experiment you might think up. |
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