[ntp:questions] Why does ntp keep changing my conf file?

Daniel Havey dhavey at yahoo.com
Thu Sep 16 18:31:39 UTC 2010


I've been looking through that /etc/init.d/ntpd script and I have bash on the brain ;^)

But no.  No firewall, only iptables and there are no rules.  Emulab sets up a VLAN between the two machines.  So there are two CentOs 5.4 machines connected to a switch, and there is a VLAN making this their own little world.

Also I just talked to the Emulab admin (sit's behind me ;^) and there is no firewall between the machines unless I set one up.

Did you mean between my testbed and ntp.aero.org/dns.aero.org (the servers in my ntp.conf file)?  There could be a firewall there but then I shouldn't be able to do this:
[dhavey at node0 ~]$ sudo ntpdate ntp.aero.org
16 Sep 11:31:08 ntpdate[13121]: adjust time server 130.221.24.100 offset 0.017606 sec

I don't think it is a firewall issue.


--- On Thu, 9/16/10, Rob <nomail at example.com> wrote:

> From: Rob <nomail at example.com>
> Subject: Re: [ntp:questions] Why does ntp keep changing my conf file?
> To: questions at lists.ntp.org
> Date: Thursday, September 16, 2010, 11:05 AM
> Daniel Havey <dhavey at yahoo.com>
> wrote:
> > Well you are right.  The init.d script does
> something that rewrites the ntp.conf file.  I don't
> understand enough bash to figure it out so I just started
> ntp manually.  It doesn't change the ntp.conf ;^)
> >
> > But it doesn't work properly either ;^(
> > First of all this looks fishy:
> > [dhavey at node0 /etc]$ ntpq -p
> >      remote       
>    refid      st t when poll
> reach   delay   offset 
> jitter
> >
> ==============================================================================
> >  cogsworth.aero. .INIT.     
>     16 u    - 1024    0 
>   0.000    0.000   0.000
> >  dns.aero.org    .INIT.   
>       16 u    - 1024   
> 0    0.000   
> 0.000   0.000
> >
> > Those delay, offset, and jitter values are too good to
> be true and the other machine won't connect:
> > [dhavey at node1 ~]$ sudo ntpdate
> node0.rms01.wgs.sntb.aero.org
> > 16 Sep 10:24:03 ntpdate[25389]: no server suitable for
> synchronization found
> >
> > Hmmm...
> 
> There is probably a firewall running that blocks all your
> NTP traffic.
> 
> Such an automatically managed system is nice, but when you
> don't understand
> it is is more of a hindrance.
> 
> There probably is some checkmark somewhere that tells the
> system to open
> up the firewall for NTP traffic and then the startup script
> for the firewall
> will write a config file just as it did for ntp, containing
> an allow entry
> for UDP port 123.
> 
> Now you only need to find where it is.
> 
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