Comments on: Why does my Linux virtual machine lose time?

By: Harald van Breederode

Harald van Breederode — Mon, 23 Mar 2009 22:11:50 +0000

Hi Dick,

I recently installed a new kernel and somehow the extra kernel arguments “clock=pmtmr divider=10″ from /etc/grub.conf were lost in this process. I re-added them and time keeping is back to normal.
-Harald

By: dikkiedick

dikkiedick — Mon, 23 Mar 2009 19:21:58 +0000

Harald,

I noticed on the training you gave last week that the time on your VMWare-servers was getting further and further behind on your Windowslaptop-time. Why was that then? As you’ve found a solution for the problem.

Greetings, Dick

By: Timekeeping in VMware… o my… « SE Stuff and the like…

Timekeeping in VMware… o my… « SE Stuff and the like… — Tue, 03 Mar 2009 10:13:37 +0000

[...] then me Marco Gralike • Prutser for breaking open the kernel discussion, good article there. http://prutser.wordpress.com/2009/02/08/why-does-my-linux-virtual-machine-lose-time/ • VMware for maintaining there KB so well • You for taking the time to read this [...]

By: Harald van Breederode

Harald van Breederode — Fri, 13 Feb 2009 08:13:34 +0000

Hi Ilmar,

Many many thanks for pointing me to this KB article. Yesterday I installed a 1000Hz kernel in both a EL4 and EL5 VMware Server VM and they both run on time with the mentioned kernel parameters, even without NTP. This saves me quite some kernel compilations.

If I knew this a week ago I didn’t have to write this posting ;-)
-Harald

By: Adrian Hollay

Adrian Hollay — Thu, 12 Feb 2009 11:53:24 +0000

Hello,

for Suse SLES running 32-bit and 64-bit kernels I am using the “clock=pit” kernel setting and just crontab to set the clock every minute using ntpdate:
* * * * * /usr/sbin/ntpdate 192.168.1.1 2&>1 >> /var/log/ntpdate.log

The offsets are very small:

…
12 Feb 12:44:06 ntpdate[24789]: adjust time server 192.168.1.1 offset 0.000422 sec
12 Feb 12:45:06 ntpdate[26079]: adjust time server 192.168.1.1 offset -0.000209 sec
12 Feb 12:46:06 ntpdate[27386]: adjust time server 192.168.1.1 offset 0.000134 sec
12 Feb 12:47:06 ntpdate[28688]: adjust time server 192.168.1.1 offset 0.007115 sec
12 Feb 12:48:06 ntpdate[29965]: adjust time server 192.168.1.1 offset -0.010231 sec
12 Feb 12:49:06 ntpdate[31267]: adjust time server 192.168.1.1 offset 0.005129 sec
…

This config works for me couple of years, already, and it is also suitable for running Oracle Clusterware on it.

Adrian Hollay

By: Ilmar Kerm

Ilmar Kerm — Tue, 10 Feb 2009 09:35:39 +0000

Yes, I have used these parameters with RHEL 3, 4 and 5 and they work. But I use only VMWare Infrastructure, not VMWare Server.

By: Paul van Eldijk

Paul van Eldijk — Mon, 09 Feb 2009 22:33:14 +0000

@ Ilmar:
Have you tried VMWare’s solutions? I’ve never gotten them to work, but OK, YMMV.

@ Harald:
It seems that more recent Linux-releases (e.g. RH-ES 5, CentOS 5) actually do work properly under VMWare

regards,
Paul

By: Ilmar Kerm

Ilmar Kerm — Mon, 09 Feb 2009 13:17:34 +0000

In VMWare KB there is an article about timekeeping in Linux.
No kernel recompilation is required.

http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1006427