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I am running on Ubuntu. I have a set of linux machines (5 to 6 machines). Which I want to combine as a single resource pool and on demand create multiple virtual instances of machines out of it.

This is comparable to what VirtualBox does in a single system. I stumbled across many key words: Xen, Eucalyptus, OpenStack etc. But things are very vague as to which will help me achieve this requirement.

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You have quite a bit to learn!

The first thing is to make sure that you understand how much resource will be needed by your virtual machines. You will need a fairly meaty machine to achieve what you want. Hard to say exactly without knowing a lot more about the specifications of the machines you are replacing.

As you have realised, there are many ways to do what you want. All the way from Open Source though to full commercial, enterprise grade, systems. I'm guessing from the phrasing that you want to err more towards the free end of things.

Almost certainly the easiest method is to use VirtualBox. It's command line tools allow you to script the creation of new machines from existing ones and there is a PHP-based web interface too that someone has created. Alternatively, one of the free versions of VMware.

With VirtualBox, the easiest way to deploy multiple instances of a virtual system from a single master image is to set the master images virtual drive to be "immutable". VB contains something called a "differencing engine", so any changes to a running system are stored in the differencing layer. By default, these changes are lost when the "system" is powered off, however, you can change this if you want to. See here for more info.

The alternative is to clone the virtual disk image. You have to use the VB command line to do this otherwise VB will not recognise the cloned image.

There are also ways to convert physical to virtual machines. Personally, I would only do this if I really had to. Better by far to create a clean image.

You can do pretty much all of this using the other tools you have also mentioned but, as a beginner, I would recommend using VirtualBox as your starting point. Once you have understood the concepts and had a go at setting everything up, I would then do some extended testing to make sure that the performance is everything you need it to be. If not, only then would I start to look at the other options.

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One of the easiest solutions I've found for hosting your virtual machines on your own hardware is Proxmox ( That doesn't necessarily help with the conversion of physical machines to virtual hard-drive images, but does help with the hosting of them after-the-fact. – killermist Jun 25 '12 at 14:33
Can proxmox make use of the computing power of multiple machines in the cluster together? And can a virtual machine span across multiple nodes ? – NS Gopikrishnan Jun 27 '12 at 5:13

Look at OpenNebula, it integrates with XCP to run multiple VMs distributed over several physical hosts, as detailed on this page.

I'm also in the research phase on the topic of virtualization. It seems there is more technology than documentation at this point.

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