title: Time sync issues with VMware guests link: https://onemoretech.wordpress.com/2008/08/19/time-sync-issues-with-vmware-guests/ author: lembobro description: post_id: 468 created: 2008/08/19 21:13:29 created_gmt: 2008/08/19 21:13:29 comment_status: open post_name: time-sync-issues-with-vmware-guests status: publish post_type: post

Time sync issues with VMware guests

I was experiencing serious time sync problems with all my Windows guests on VMware Server, which was causing me no end of grief when reading fast-incoming mail on my Outlook client in one of those guests.

There’s this VMware tome on what turns out to be a very complex subject, but I found that on the free VMware Server v1.0.5 and above the following solution works:

1. Install VMware tools in the guest.

2. Edit the .vmx file on your host for the guest to include the following line:

tools.syncTime = "TRUE"

3. Edit /etc/vmware/config on your host and add the following lines:

host.cpukHz = "2800000" host.noTSC = "TRUE" ptsc.noTSC = "TRUE"

The host.cpuKHz value should be approximately the same as your real CPU’s clock speed (if it was advertised as 2.8 GHz, as mine was, put in an even 2800000 - on Linux do a cat /proc/cpuinfo, for most Intel processors the speed is noted in the “model name :” line).

What happens behind the scenes is that your VMware guest’s clock will run just a tad slower/faster than your actual host clock, which VMware Tools will respond to by dynamically adjusting as necessary.

In actual practice I’ve found that my own guests don’t run much slower than a couple of minutes when this solution is applied — much better than the 10 or 15 minutes they would get out of sync after a few days.

By the way, this problem doesn’t occur at all with any of my Linux VMs, since they’re all configured to do constant ntp updates on their own.

Thanks to Adrian Bradshaw for pulling together the links for this solution and giving his own succinct step-by-step instructions for implementing it.

Copyright 2004-2019 Phil Lembo