How to Create Linked Clones in Virt-Manager (GUI)

If you run virtual machines locally using QEMU/KVM, you should be using Linked Clones.

Instead of copying a 2GB+ master template file over and over (which takes time and wastes SSD space), a linked clone creates a tiny, empty file (often just a few kilobytes). It treats your master template as a read-only base layer.

• When the VM reads data, it reads from the master.
• When the VM writes data, it writes only to the new, tiny clone file.

Creating linked clones via the command line is simple (qemu-img create -b ...), but trying to do it entirely within the Virt-Manager GUI can be incredibly confusing. There is no simple "Linked Clone" button.

Here is the exact workflow to achieve this using Virt-Manager's Storage Pools and Backing Stores.

The Secret: Storage Pools

Virt-Manager is very strict about where files live. To create a linked clone in the GUI, both your master template and your new clone must live inside recognized Storage Pools.

If you just leave your master template in your ~/Downloads folder, Virt-Manager's UI will not let you select it as a backing file.

Step 1: Create a Template Pool

Let's create a dedicated, organized space for our master OS images.

1. Open Virtual Machine Manager.
2. Go to Edit (in the top menu bar) and select Connection Details.
3. Click the Storage tab.
4. Click the + (Add Pool) button at the bottom left.
5. Name the pool templates and set the Type to dir: Filesystem Directory. Click Forward.
6. Set the Target Path to a clean directory (e.g., /home/youruser/VMs/templates) and click Finish.

Now, use your regular Linux file manager (Nautilus, Dolphin, etc.) to move or copy your master .qcow2 image into that new folder.

⚠️ Crucial Warning: Never boot a VM directly from this master template! If the master file gets modified, any linked clones relying on it will break instantly. Keep this file pristine.

Step 2: Generate the Linked Clone

Now that Virt-Manager knows where your templates live, creating the clone is easy.

1. Still in the Connection Details -> Storage window, select your default active pool on the left (usually called default, pointing to /var/lib/libvirt/images/). This is where you want the actual VM to live and run.
2. Click the + (New Volume) button located above the volume list.
3. Configure the new volume:
   • Name: my-new-vm-disk.qcow2 (or whatever you prefer)
   • Format: qcow2
4. Look at the bottom of this window and expand the Backing Store section.
5. Click Browse... next to the backing store path.
6. In the window that pops up, select your templates pool from the left menu.
7. Click on your master .qcow2 file and click Choose Volume.
8. Click Finish.

Virt-Manager will instantly generate the tiny, linked clone disk inside your active pool. It acts as a lightweight delta layer pointing directly to your master template!

Step 3: Build the VM

Finally, let's attach our new linked clone to a VM.

1. Close the Connection Details window.
2. Click the New Virtual Machine button (top left icon).
3. Select Import existing disk image and click Forward.
4. Click Browse... and select the my-new-vm-disk.qcow2 you just generated in your active pool.
5. Finish the setup wizard by allocating RAM and CPUs.

That's it! You have successfully deployed a space-saving linked clone entirely within the Virt-Manager GUI.

What's Next?

If you are using this method to provision cloud images (like Ubuntu Cloud or Amazon Linux), check out my full guide on How to Run Amazon Linux 2023 Locally with QEMU/KVM and Cloud-Init to learn how to inject your SSH keys and configure your instances on first boot!

Found this helpful? Follow me for more real-world Linux troubleshooting and DevOps content.

Originally published on khadirullah.com