Linked Clone in VirtualBox, What is it and How to Clone Virtual Machine?

Cloning is one of the important feature every virtualization software must have. Oracle VirtualBox started to carry this feature from latest major release 4.1. This article explains about clone especially linked clone in VirtualBox and how to clone virtual machines.

Oracle’s powerful open source desktop virtualization software VirtualBox came up with new features in major release 4.1, I already covered them when it was in beta stage. Also when I conveyed my personal opinion on missing options in VirtualBox, the cloning was one of the feature from beginning whereas VMware and Parallels software are having it. Even though there is a manual method to clone a virtual machine in virtualbox, but it is a difficult task for normal users.

What is Clone/Cloning?

Cloning is a process of creating a new virtual machine by copying the existing one. It will copy the virtual hard disk file (VDI) and configuration files in to new location. This helps in reducing the time and disk space for creating similar virtual machines.

Here is an example,

You have installed Windows 2003 server OS in VirtualBox as guest machine and done the all updates and driver installation. Now, you need to have another two similar virtual machines to have a domain controller testing setup.

The existing original Windows 2003 server virtual machine consumed 8GB disk space in host and 2 hours to complete the entire setup (Windows updates, drivers and Guest additions). Now, how are you going to make another two virtual machines? here comes ‘cloning feature’. If you do not have clone feature in virtualization software then you need to waste another 16GB host disk space (8GB x 2) and 4 hours (Of course you can start the installation in both virtual machines simultaneously, but somehow you need to spend extra time). By using cloning this requirement can be fulfilled very easily and quickly.

There are Two Types on Cloning Available

1) Normal Clone

2) Linked Clone

If you want to create similar two 2003 server virtual machines by normal clone, then you will need 16GB host disk space but less time. Because it will create new virtual machines by copying the 8GB VDI hard disk file. So, you are saving the time by skipping installation of OS, drivers and updates which consumed 2 hours.

Linked clone is more advance and helpful. If you use linked clone feature in Oracle VirtualBox to create these two new virtual machines, then it will take very less host disk space, let’s say 10MB (5MB per VM) and very less time too. Because this will create a separate small sized ‘linked’ virtual hard disk to original (first Windows 2003 OS VM) VDI 8GB file. So, the new cloned virtual machines will be working with ‘linked’ virtual hard disk and all new changes will be saved in newly created disk. But, the original source VDI file must be available in same place. Finally, you save huge amount of disk space and time by linked clones in this example.

To understand more about the advantages of linked clones, check this guide.


How to Create Linked Clone in VirtualBox

1) It is very simple, just right click on the virtual machine and click clone.

linked clone in virtualbox


2) Give the name for new virtual machine. It’s always better to select ‘Reinitialize the MAC address of all network adapters’ to have an unique MAC address for the virtual machines in a network.

3) Next option is to select the clone type. I have already explained the different between these two types. Here we select Linked clone and press Clone.

Once you create the clone successfully, you can see an additional notification on original virtual machine which is stating that this machine is a Linked Base for particular another VM. Therefore, if you delete or move the original virtual machine then the linked clone virtual machine will not work.

desktop virtualization software


Also, you could see an additional snapshot created in original VM automatically. In fact, this snapshot will be the base for cloned virtual machine, because the new changes you make in original virtual machine should not effect the other linked cloned virtual machines. Therefore, the particular snapshot should be safe for the smooth running of cloned virtual machine.

linked clone snapshot


Now, the original and cloned VMs will work perfectly and any changes can be done on these machines. But, technically the original VM’s base file and particular snapshot should be untouched and protected.

So, Oracle VirtualBox has become more powerful and advanced free desktop virtualization software with cloning feature. No doubt this will be the great feature for learners and testers who wants to have multiple virtual machines.

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