Comments on: Cloning VirtualBox VM Snapshots

By: Jonathan Dickinson

Jonathan Dickinson — Tue, 28 Jun 2011 16:52:58 +0000

Ah I just read up on it on Wikipedia and it looks like my previous literature was incorrect – Type 1 hypervisors are the ones I was thinking about (where Type 2 are user-space applications such as VBox).

By: Oded

Oded — Tue, 28 Jun 2011 09:05:45 +0000

Thanks for the comment, but I don’t think you are right in this – a hypervisor is not an operating system: both ESXi and Xen are software stacks that run on top of an operating system – the commercial products actually package a small Linux distribution and install that “underneath” the hypervisor.

Technically term “hypervisor” is currently used to mean the software that interacts with the CPU to run another operating system in “protected mode” that is protected from the host operating system (whether it is a prepackaged light weight Linux or an operating system that is used to run other things such as a graphical desktop), and in that sense both VirtualBox and HyperV are fully qualified hypervisor. You can say that commercially you prefer to use the term “hypervisor” to only mean products that run on top of a packaged operating system and do not let you access the host operating system as a general purpose computing platform, but I don’t think that is technically correct.

By: Jonathan Dickinson

Jonathan Dickinson — Tue, 28 Jun 2011 08:53:07 +0000

FYI: VBox is not a hypervisor – things like ESXi and Xen are hypervisors (because they don’t run inside your primary operating system a.k.a. domain0, your primary operating system runs in them) – funny thing is Microsoft HyperV fails to qualify as a hypervisor because it runs partially inside domain0 .

At any rate thanks for the article, most helpful.

By: David

David — Fri, 26 Feb 2010 20:38:52 +0000

Thank you Oded – just what I wanted to know

By: Oded

Oded — Fri, 26 Feb 2010 11:59:28 +0000

With VirtualBox 3.1 It will be as you plan. The way to do it is:
1. install your base OS, then shut it down and get a snapshot.
2. Run your VM and install whatever extra stuff you need, then shut it down and take a snapshot.
3. Choose the first snapshot from VirtualBoxe’s Snapshots tab and click “Restore”. It will warn about losing the current state so just OK that (the current state is identical to the last snapshot).
4. Now run the VM and install other extra stuff that you need, shut it down and take a snapshot.

What you will have then is 3 snapshots:
- Snapshot 1: Just your base OS ready to install other stuff
- Snapshot 2: Base OS with software setup A – you can always restore to it and boot your VM and you’ll get that setup.
- Snapshot 3 (from step 4 above): Base OS with software setup B – you can always restore to it and boot your VM and you’ll get that setup.

Also – when you’re done with one setup and want to switch to the otherside of the fork, don’t bother shutting down properly – just close the VM and tell it to “restore to snapshot” and then it will revert to how it was just after the snapshot – ready to be run again with no messy shutdown process, and no “current state” to worry about. You can also get the snapshot while the VM is running, and then when you restore to the snapshot and power on the VM it will immediately be running!

I personally am still using my original setup (before VirtualBox 3.1) because I want the ability to run both copies of the setup at the same time .

By: David

David — Fri, 26 Feb 2010 01:14:57 +0000

If you “fork” as per your “Update” at the end of your article, is the old ‘head’ retained or do you lose it?

What I want to do is create a ‘base OS install’ and then fork different VMs from that, so I only install the OS once. I don’t want to damage my existing VMs if I fork from this base state at a later time.

By: Oded

Oded — Thu, 30 Jul 2009 07:48:20 +0000

Yes, but that would export what is called the HEAD in SCM terms. For my purpose though, which is creating different VMs with different configurations: For example on one VM I’d install Flash Player 9 and on another I’d install Flash Player 10.

What I can do is take a snapshot after I got base working and before installing my target configuration, then install the target configuration and clone the HEAD (latest configuration). Then I’d revert back to base and install a new configuration.

Good idea – it’d probably be easier then the process I described above.

By: Robert Lancer

Robert Lancer — Thu, 30 Jul 2009 04:44:27 +0000

You can also export a virtual appliance of the latest snapshot and that consolidates it very well into one VDI