Virtual PC: Issues with clock when guest Linux has a different timezone to the host OS

Question

I'm running Linux (Centos) under Virtual PC in Windows 7.

Guest is set to a different time zone then host OS and none of them are UTC.

The issue is that when guest boots its time is always set to the host OS time but time zone is still whatever guest uses eg
host is 14/5/2011 09:00 NZST,
guest after booting becomes 14/5/2011 09:00 CDT (same relative time as host but different TZ)
where it should really be 13/5/2011 16:00 CDT (same absolute time).

Basically on each boot time jumps forward and correcting it later causes all sort of issues like crashed imap server and so on.

As far as i understand it happens because /etc/sysconfig/clock allows only two options for a clock setting: use hardware clock (host OS clock) as is (ie local time) or as UTC time, so i cant see a way to fix on the guest side.

Is there any way so specify time zone for a guest on virtual machine level? Maybe Virtualbox or VMWare does allow something like it?

Answer 1

Not convinced the other softwares would change anything as it sounds like the regional settings of your (host) computer are being inherited.

A common solution would be NTP (Network time protocol)

Try installing NTP on CentOS and configuring it to pull the correct time and date from a time server/ntpd.

Tutorial here: http://www.cyberciti.biz/faq/howto-install-ntp-to-synchronize-server-clock/

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Comment included: "@alexeit I only describe this as a solution as I hit the same problem with a virtual host company once based in the US hosted my system. I needed a GMT/UTC0 timezone and as such had to configure NTP to solve my issue as I could not control the timezone/time of the VM host.

Additional to my last comment: Sorry this was a while back - I do actually recall having to create a start up script to 'soft' set the timezone correctly then sync with NTP."

Answer 2

Fresh answer. I have just tested this on Ubuntu not CentOS but the same principal applies.

As you mentioned there are two clocks - The hardware clock and the UTC (I generally think of this as OS level) clock.

The virtual machine host controls the hardware clock and in live environments it may not always be possible to change this (for example a VPS). So instead, I recommend using NTP to keep the time synchronized based on the timezone of your VM.

Step 1. [May not always be required] Set the timezone on your OS using /etc/localtime (It's possible to use CentOS' redhat-config-date or just setup). Further details please see: http://www.cyberciti.biz/faq/howto-linux-unix-change-setup-timezone-tz-variable/

Step 2. To test this then synchronizes, use ntpdate utility along with your chosen time server. You should find when you type date the expected output with correct time and zone is received.

ntpdate [server]

Step 3. Either set a daily crontab to run the same ntpdate command or install and configure ntp daemon to keep the time in sync on a more regular basis.

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In testing, my host was BST (British Standard Time) and was showing as Mon May 16 00:00:00 BST 2011 on the hardware clock which initially inherited to the virtual system.

I then changed /etc/localtime to a symbolic link of Japan JST and rebooted. Time now shows as Mon May 16 08:01:00 JST 2011.

I purposely put the time out of sync by several hours (date -s "15 May 2011 16:00:00") Time now shows as Sun May 15 16:00:00 JST 2011.

I then ran ntpdate ntp.ubuntu.com Time now shows as Mon May 16 08:04:00 JST 2011