Time Service on Hyper-v SBS Server

Posted: September 1, 2011 in General Blog Comments, Hyper-v, SBS 2008, SBS 2011, Virtual Machine, Virtual Machines, vm, Windows 7, Windows Time Server

I was pulling my hair out, wondering why the clock on client machines in a SBS 2011 domain were off about 5 minutes fast.  Surely the server time was the issue, and I kept resetting it only to see it go back to its five minutes fast setting again.  So I rolled up my sleeves, dug into all the command options of w332tm and registry settings, and they all looked fine.  My server was set to use time.windows.com.

Why didn’t this work?

I finally paid attention to the result of this command:

w32tm /query /status

I slapped my forehead and also did another command

w32tm /query /source to amplify the results I was looking for

Here is what I got

Since I had set the time server to time.windows.com, I was puzzled why that time server did not show up and what the heck was VM IC Time?  Almost instantly it hit me: the hyper-v SBS 2011machine was getting its time from the host, and my settings were not overriding that.

Sure enough, I looked at the host machine (not part of the domain) and it was not using an authoritative time server and was – gasp! – about 5 minutes fast.  A few simple things fixed it all.

On the Hyper-v Host

From either the control panel or time in systray, set the computer clock.  Click on the Internet Time tab and if it is not set to synchronize, click Change Settings…. In the dialogue box that appears, click the Synchronize box and leave the server as time.windows.com or change to another value.  Click update now button, then OK to close.  Click OK again.

On the SBS 2011 Server

Open a command prompt in elevated mode (run as administrator).  Enter this command

w32tm /resync

You should see the clock change to match the value on the hyper-v host machine.

On Client Machines

You will see the time change when the client machines follow the time synchronization schedule, but you can do it immediately if you want.  Use the procedure above for the SBS Server but on your client machines.

That’s it.

There’s Another Way……

This made me think, there’s gotta be another way to deal with this.  Sure enough, a bit of snooping led me to play with the hyper-v host settings, and here is a way to let your SBS 2011 hyper-v machine throw off the shackles of the host time server.

On the hyper-v management console, click on the SBS 2011 server and choose settings.  On the left hand pane under Management, click on Integrated Services and clear the check mark next to Time Synchronization then OK or Apply.  You can actually do this while the hyper-v machine is running.

Once you have done this, log onto the SBS 2011 server, run command prompt and type

w32tm /query /source

You should now see the source changed to time.windows.com or whatever other time server source you have configured.

Either method you choose will work, but I prefer the change in Integration Services to make your SBS server less dependent on its host.

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