Linux – CentOS 5 clock running twice as fast

centoscentos5linuxtime

The system clock on a CentOS 5 install is running twice as fast as it should. The hardware clock is fine, and when I run a ntp sync, it resets to the correct time. But within 2 minutes, it is already 2 minutes too fast. The OS is not running virtualised, this is a native CentOS install on an AMD Opteron server.

Any clues?

Best Answer

Can you provide the specific version of CentOS 5 as well as the server manufacturer and model. That may help...

But one thing you can try on CentOS 5 is appending clock=pmtmr to the end of your kernel boot line in the Grub menu or in /etc/grub.conf and restarting the system. Explanation here.

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Linux – Server clock running too slow

You can resolve the problem by running NTP. If it isn't already installed you should be able to do something like

  yum install ntp
  chkconfig --levels 235 ntpd on
  service ntpd start

You may have to give it a while to sync the first time.

Linux – the largest hardware clock update the Linux kernel “11-minute mode” can make

From the hwclock man page on RHEL 4.6:

This mode (we'll call it "11 minute mode") is off until something turns it on.  The ntp
daemon  xntpd  is  one thing  that  turns  it on.  You can turn it off by running
anything, including hwclock --hctosys, that sets the System Time the old fashioned way.

To see if it is on or off, use the command adjtimex --print and look at the value of
"status".  If the "64" bit of this number (expressed in binary) equal to 0, 11 minute mode 
is on.  Otherwise, it is off.

So by the virtue of you running hwclock --set you have likely turned it off. By the same token you can check the output of the adjtimex --print to confirm.

Best Answer

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