Extending the System Drive on Windows 2008 Running Under KVM

While I was writing this post I first allocated 15GB for my Windows install. I quickly realized that after a plethora of updates that is not enough space. Luckily it’s pretty easy to remedy that with a two step process.

1. Increase the Underlying Hard Disk IMG file Used in KVM

Shutdown the VM and then using virsh figure out the full path of the IMG file used by the desired VM. Here is a list of all the VMs that are powered off:

[virtuser@kvm ~]$ virsh -c qemu:///system list --inactive
 Id Name                 State
----------------------------------
  - VM1                  shut off
  - VM2                  shut off
  - kelatov_Win2k8       shut off
  - kelatov_win7_2       shut off

Let’s see we wanted to resize the Hard Disk of the “kelatov-win7-2” VM. So go ahead and find out where the IMG file is for that VM:

[virtuser@kvm ~]$ virsh -c qemu:///system domblklist kelatov_win7_2
Target     Source
------------------------------------------------
hda        /images/kelatov_win7_2.img
hdc        -

Now let’s make sure the size of the file is 15GB like we expect:

[virtuser@kvm ~]$ ls -lh /images/kelatov_win7_2.img
-rw-------. 1 root root 16G Jun 21  2012 /images/kelatov_win7_2.img

That looks correct. Now let’s go ahead and add 5GB to the IMG file:

[virtuser@kvm images]$ sudo qemu-img resize kelatov_win7_2.img +5G
Image resized.

Let’s make sure the new size shows up:

[virtuser@kvm ~]$ ls -lh /images/kelatov_win7_2.img
-rw-------. 1 root root 21G Jun 21  2012 /images/kelatov_win7_2.img

2. Extend the Volume Inside the Windows 2008 OS

Power on the VM and from within Windows run:

diskmgmt.msc

And you will see the following:

Then right click on the C: partition and then select “Extend Volume”:

Then the “Extend Volume Wizard” will startup:

Click “Next” and it will automatically select the available space on that disk:

In our case we have 5GB available which as I mentioned is automatically selected. At this point just click “Next” and then “Finish”. After the process is finished, you will see the C: partition take up the rest of the drive:

Now we can apply more updates :)