Xen virtual machines and ntp

[Schaffrath, Rene]

Hello,

have you tried to set "xen.independent_wallclock=1" in
/etc/sysctl.conf (activate with sysctl -p).

No time drifting in our domUs - even under very high cpu load...

Hope this helps,
René


> -----Original Message-----
> From: redhat-list-bounces at redhat.com 
> [mailto:redhat-list-bounces at redhat.com] On Behalf Of ESGLinux
> Sent: Wednesday, May 13, 2009 9:14 AM
> To: General Red Hat Linux discussion list
> Subject: Xen virtual machines and ntp
> 
> Hi,
> 
> I´m running a  Xen server with several virtual machines on 
> it. I have a
> problem with the time of the machines.
> They unsynchronize very fast (in an hour several seconds). I 
> try to use ntpd
> to syncronize them but It doesn´t work.
> 
> I have set up a local ntp server with this ntp.conf:
> 
> #grep  ^[^#] /etc/ntp.conf
> restrict default kod nomodify notrap
> restrict 192.168.1.0 mask 255.255.255.0 nomodify notrap
> server 1.rhel.pool.ntp.org
> server 2.rhel.pool.ntp.org
> server 127.127.1.0
> fudge   127.127.1.0 stratum 10
> driftfile /var/lib/ntp/drift
> keys /etc/ntp/keys
> restrict 1.rhel.pool.ntp.org mask 255.255.255.255 nomodify 
> notrap noquery
> restrict 2.rhel.pool.ntp.org mask 255.255.255.255 nomodify 
> notrap noquery
> server hora.roa.es
> restrict hora.roa.es mask 255.255.255.255 nomodify notrap noquery
> 
> and the clients like this:
> 
> restrict default kod nomodify notrap nopeer noquery
> tinker step 0
> restrict 127.0.0.1
> restrict -6 ::1
> server 192.168.1.1
> server 0.rhel.pool.ntp.org
> server 1.rhel.pool.ntp.org
> server 2.rhel.pool.ntp.org
> driftfile /var/lib/ntp/drift
> keys /etc/ntp/keys
> restrict 0.rhel.pool.ntp.org mask 255.255.255.255 nomodify 
> notrap noquery
> restrict 1.rhel.pool.ntp.org mask 255.255.255.255 nomodify 
> notrap noquery
> restrict 2.rhel.pool.ntp.org mask 255.255.255.255 nomodify 
> notrap noquery
> restrict 192.168.1.1 mask 255.255.255.255 nomodify notrap noquery
> 
> 192.168.1.1 is the first machine, the one I want to be the 
> ntp local server.
> 
> the param tinker step 0 I get from this
> http://wiki.dovecot.org/TimeMovedBackwards
> My real problem began with dovecot, because if the machine is not well
> syncronized the dovecot kills itself ( dovecot: Time just 
> moved backwards by
> 8 seconds. This might cause a lot of problems, so I'll just 
> kill myself now.
> http://wiki.dovecot.org/TimeMovedBackwards)
> 
> 
> so, I have two questions:
> 
> 1 - Why my virtual machines unsynchronize so quickly?
> 2 - What am I doing wrong with ntpd?
> 
> thanks in advance
> 
> ESG
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