problem on upgrade 10.04 to 12.04

[satimis]

Hi all,

Following guide;
Upgrade to Ubuntu 12.04 from Ubuntu 10.04 via the Terminal
http://www.liberiangeek.net/2012/04/upgrade-to-ubuntu-12-04-from-ubuntu-10-04-via-the-terminal/

worked for me to upgrade all Ubuntu 10.04 to 12.04 on all VMs of VirtualBox.

But it didn't work on Guests of KVM.

$ sudo do-release-upgrade

Checking for a new ubuntu release
No new release found


$ lsb_release -a

NO LSB modules are available
Distributor ID: Ubuntu
Description: Ubuntu 10.04.4 LTS
Release: 10.04
Codename: lucid


Pls help. TIA

B.R.
satimis