Это бага в бубунте 8. Надо поправить /etc/hosts прописав туда
127.0.0.1 localhost alex-linux
Можно сделать это, загрузившись с live-cd или
system > Administration > Network
> unlock the widow with your password > go to the tab Host, on the second part of the the first line ( 127.0.0.1 ) type / replace the missing host by your host name, in my case that was jp-desktop the host given during the install.