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maulermark
Contributor
Contributor

Independent nonpersistent snapshots

We're running several Windows XP and Windows 2003 server guest VMs in a classroom setting. After class is over the instructor wants to reset the VMs back to default. We initially configured the disks as independent, nonpersistent with the idea that the students could reboot the VMs during class and keep all changes made, but a shutdown at the end of class would reset the disks back to the default setup. This worked well initially.

Now the instructor wants to snapshot the VMs at the end of each day as a fallback point in case of the VM accidently getting shutdown and reset back to defaults. Each daily lab in class builds upon the others and a power failure or accidental shutdown would lose all work in progress.

My testing has shown that I am unable to apply a snapshot taken on the independent nonpersistent disk since the disk changes are discarded when the VM is powered down. I am unable to snapshot memory and receive an error message when trying.

Am I missing something? Is it possible to take snapshots and apply them to independent nonpersistent disks to get back to previous configuration without resetting the disk back to defaults?

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a_p_
Leadership
Leadership

"Independent disks are not affected by snapshots"

That is what you see in the virtual machine's settings when you select the disk.

One way to achieve what you need would easily be possible by changing the disk mode to non-independent and taking an initial snapshot.

After each class you could revert to the initial snapshot (manually or scripted)

This way the data is persistent until you "reset" the VMs.

André

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continuum
Immortal
Immortal

I found a workaround ...

You can setup your VMs in such a way that the VM will ask you if you want to keep or discard the changes you have done during last usage.

But this comes with a very high price - you must run the VM as very old virtual hardware

and I mean really very old Smiley Wink

config.version = "6"
virtualHW.allowVeryOldVersion = "TRUE"

see http://sanbarrow.com/vmx/vmx-undoable-mode-for-vmserver.html






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Do you need support with a VMFS recovery problem ? - send a message via skype "sanbarrow"
I do not support Workstation 16 at this time ...

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