I am using OS 12.04 version, but using upgrade command results in the desktop being changed for the new version 13.04.How do I downgrade to the old version using the command-line?From this:root@metal004:~# lsb_release -a  No LSB modules are available.  Distributor ID:   Ubuntu  Description:  Ubuntu 13.04  Release:  13.04  Codename: raringTo:root@metal004:~# lsb_release -a  No LSB modules are available.  Distributor ID:   Ubuntu  Description:  Ubuntu 12.04.3 LTS  Release:  12.04  Codename: precise
how to downgrade in command line for ubuntu?
ubuntu;upgrade