Offline upgrade from 12.10 to 13.04 using installation disk won't work
Fresh Ubuntu 12.10, fully updated, in a test virtual machine. What I'm trying to achieve is to upgrade from 12.10 to 13.04 **without** an Internet connection.
Steps to replicate:
1. In a virtual machine, install a clean, fresh Ubuntu 12.10 system. Apply all available updates;
2. Shutdown the VM;
3. Disconnect network cable from the VM (this is an option in VirtualBox). Make sure your VM has no Internet link;
4. Insert the Ubuntu 13.04 beta 2 installation ISO in the VM. Reboot the VM;
5. Select your desired language, and click "Install";
6. On "Preparing to install Ubuntu" screen, make sure again that you see no Internet connection available. This prerequisite should be marked by an X on this screen. If an Internet link has been found by Ubiquity, disable this connection before continuing;
7. Then, on "Installation type screen", observe that the "Upgrade Ubuntu 12.10 to Ubuntu 13.04" option is greyed!!! It cannot be selected.
What is strange is the upgrade option as again available if an Internet connection is found by the installer. Repeat the previous steps, but this time, make sure your VM has an Internet link. Back on the "Installation type" screen, the upgrade option can be selected.
Is this a bug in Ubiquity? Is it normal -- the expected behavior -- for Ubiquity to require an Internet connection in order to performe an upgrade from Ubuntu 12.10 to 13.04?