How to convert VM disk from qcow2 to raw format

This article provides a 5 step process to convert an existing virtual machine disks format from qcow2 to raw format.

NOTE: This article assumes to have existing Virtual Machines (VMs) in order to following these steps!

1. Backup current virtual machine config

   virsh dumpxml vm-name > vm-name.xml

   replace vm-name with your virtual machine name. In this example, we will use the virtual machine 'alpha':

   root@vmsvr# virsh dumpxml alpha > ~/alpha.xml

   If you are unsure or just want to double check the virtual machine name, you can find this information by running the following command:

   virsh list --all

   for example:

   root@vmsvr# virsh list --all
    Id   Name          State
   ------------------------------
    1    alpha         running
    2    bravo         running
    4    charlie       running
    5    echo          running
    12   foxtrot       paused
    -    golf          shut off
    -    vmtest        shut off

2. Find the path of the exisiting disk image

   virsh dumpxml vm-name | grep file

   in our example:

   root@vmsvr# virsh dumpxml alpha | grep file
     <disk type='file' device='disk'>
       <source file='/var/lib/libvert/images/alpha/tmplEzSU838.qcow2'/>

from the about output, we can confirm that our disk image is named '/var/lib/libvert/images/alpha/tmplEzSU838.qcow2'


3. Convert the disk image

   qemu-img convert <image-name>.qcow2 <image-name>.raw

   in our example:

   root@vmsvr# qemu-img convert /var/lib/libvert/images/alpha/tmplEzSU838.qcow2 \
                     /var/lib/libvert/images/alpha/tmplEzSU838.raw

4. Edit the VM config

   virsh edit <vm-name>

   then find the driver and source lines:

      <disk type='file' device='disk'>
         <driver name='qemu' type='qcow2'/>
         <source file='/var/lib/libvert/images/alpha/tmplEzSU838.qcow2'/>
         <target dev='vda' bus='virtio'/>
         <address type='pci' domain='0x0001' bus='0x00' slot='0x04' function='0x0'/>
      </disk>

   replace qcow2 with raw in the highlighted places. The changes should look something like:

   <disk type='file' device='disk'>
         <driver name='qemu' type='raw'/>
         <source file='/var/lib/libvert/images/alpha/tmplEzSU838.raw'/>
         <target dev='vda' bus='virtio'/>
         <address type='pci' domain='0x0001' bus='0x00' slot='0x04' function='0x0'/>
       </disk>

   save changes and exit the editor.
   
   
5. Start the VM

   virsh start vm-name

   in our example:

   root@vmsvr# virsh start alpha