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ldigioia

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Hi guys,

I have been troubleshooting this problem for about a month now. I am running Linux guests on Windows 10 Hyper-V hosts. 

Creating mainly Debian Linux guest VMs, when I am all done and allow the Windows host to sleep - the VM will automatically save just fine. When the Windows machine wakes, the Linux VM also does. However, the time in the VM will be whatever time it was when it slept.

All I need to do to correct this is save it and restart it, then time is correct. Or, within the guest, change any time sync setting, and it snaps back to the correct time immediately. Rebooting the guest or host obviously works too. It is only the sleep/wake situation where the guest loses sync. I have looked at event logs on the host, nothing interesting there. This is all completely new hardware, completely clean installs - the problem is easily reproducible, even after re-installing both host and guest.

I actually have another Windows 10 host that does NOT have this problem - and it is older hardware. I also tried another fresh install on another late model Windows 10 machine here, same problem. I explored all the Hyper-V guest extension support modules and so on - and verified multiple times that they are installed and running correctly in the guests. The correct and necessary modules are baked in to Debian 8.6. Even so, since MS appears to favor CentOS a bit more support-wise, I tried a CentOS guest - same issue exactly.

This is an annoying problem, but it is not intermittent and seems like it should be easily fixed - what am I missing? Thanks.

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wobble_wobble

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Reply with quote  #2 
Can't answer why its doing the time issue.

but a solution is to ge tthe guests to use an external NTP source for their time.

From a Debian Wiki - https://wiki.debian.org/NTP
From a tech support page - https://support.rackspace.com/how-to/using-ntp-to-sync-time/


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ldigioia

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You would think. But no, internal or external makes no difference. Changing the setting either way makes the time sync instantly. Saving the machine and starting it up again fixes it. The problem only occurs after sleeping. I also forgot to add that of course it does not happen with Windows guests.
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wobble_wobble

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Reply with quote  #4 
You probably have, but my next suggestion is the Hyper-V Linux integration tools...
https://www.microsoft.com/en-ie/download/details.aspx?id=46842

If you have tried, and that doesn't work, have you tried a Server OS as the laptop OS and see what happens?


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ldigioia

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Reply with quote  #5 
Sure, one of the first things I looked at were those tools, but after much study and testing I verified that they are already built-in and running. There is no laptop. It is a desktop computer, and to run a server OS would defeat the purpose. I have tried the same Linux distributions on Hyper-V 2016, and they are fine - but a server OS does not sleep.
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wobble_wobble

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Reply with quote  #6 
I suspect you've come across some of the limitations of Hyper-V on a client OS.

I'd suggest you add in a scheduled task on the Linux guests to check the NTP Server regularly...
Crontab tasks - http://www.howtogeek.com/101288/how-to-schedule-tasks-on-linux-an-introduction-to-crontab-files/


With regard to sleeping/ hibernation on a Server OS, my laptop with 2012R2 will differ.
Runs like a pig post wake-up, but then again runs like a pig anyway [smile]


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ldigioia

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Well, you nailed it. It turns out that my NTP setting actually takes a reboot to take effect - (although I am sure I could have restarted a process.) And the default poll is 64 seconds, which I was never patient enough to wait for. I changed it to 10 seconds and I am fine now. Thanks.
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wobble_wobble

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NP and welcome to the forum!


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