ESX Server system time jumps +2 hours when rebooting

[Haseldow]

Hi,

Whenever I reboot any of my ESX hosts the system time jumps forward by +2 hours. I guess it's because the OS gets the time from BIOS and adds time zone (GMT +2) to the time or something similar.

This is probably a trivial problem, but I can't seem to find any good solutions for it. I would rather not configure ESX to update from a NTP server. Any help appreciated.

-Haseldow

"Never underestimate the power of stupid people in large groups"

[jhanekom]

My guess is that you set the "System clock uses UTC" option during ESX installation, but that a combination of that setting, the fact that the system clock is not set to UTC and the time zone on your ESX host causes the behaviour you're seeing.

Can you take a look in /etc/sysconfig/clock and see what the ZONE and UTC settings are set to?

[Haseldow]

Thanks jhanekom, you were correct I had "UTC=true".

"Never underestimate the power of stupid people in large groups"

[jhanekom]

Cool - did that actually fix the problem? It was an (educated) guess, so if you haven't yet rebooted I wouldn't get too happy just yet.

[Haseldow]

No, I didn't reboot, but the answer is logical.

"Never underestimate the power of stupid people in large groups"

[jhanekom]

The following post goes into quite a lot of details about why you SHOULD set UTC=true: http://communities.vmware.com/message/623206

You need to then make sure that the timezones on the ESX host as well as your VMs are set correctly.

Also, as a best practice you should synchronise your ESX host with at least one (preferably a couple) of reliable time sources. You seem to not like this idea... may I ask why?

[Haseldow]

After I rebooted the ESX servers and the system clock skipped forward by two hours, I migrated all of our windows domain controllers to that host. This caused the windows domain controlelrs to synchronize their clock from the ESX host and do the two hour time travel to the future as well. This in turn caused all windows users not to be able to access any network resources or services. This was a major problem for us and caused a lot of wasted time and money.

I don't want to have ESX servers to update time from time servers as I do not want to open any ports to the ESX servers themselves. This does not in any way mean that I'm against ESX hosts synchronizing time, or that I wouldn't do it in the future. I just don't feel like it's that critical and the server clock itself seems to be accurate enough for me. All virtual machines synchronize time from our own time servers.

"Never underestimate the power of stupid people in large groups"

[jhanekom]

You don't need to "open any ports" to the ESX servers to allow them to synchronise time. You also don't need to synchronise time with an external source. What's more important is that they synchronise to the same source as the rest of your internal network. An internal router is a common source for smaller setups.

(If you'll be putting your domain controllers on ESX and want to sync ESX with the same source as the rest of your network, it might be a good idea to leave the PDC emulator role on a separate physical machine for timekeeping reasons - don't synchronise ESX with a VM!)

You'd do well to read through the following paper: http://www.vmware.com/pdf/vmware_timekeeping.pdf

It's also a good idea to disable the Windows Time service on your VMs if you synchronise your VMs clocks with ESX (which, in my opinion, is a good practice.) Two conflicting time synchronisation methods are not a good idea.