Installing LinuxCNC 2.8 on Ubuntu Precise

Following the html documentation at:
linuxcnc.org/docs/2.8/html/getting-start...ng_on_ubuntu_precise
on a fresh install of Ubuntu Precise (3.13.0-117-generic) I was able to get LinuxCNC 2.8 installed and running, but with some minor deviations from the docs. Section "7.4 Installing on Ubuntu Precise" does not mention bringing up the GRUB menu on startup or editing /etc/default/grub which is needed to select the RTAI kernel (3.4-9-rtai-686-pae) just installed. The RTAI kernel disables networking so the advice to boot into it, and then run "sudo apt-get install linuxcnc" does not work, because this command needs the network. I found it necessary to install linuxcnc before rebooting into the RTAI kernel. Is this sequence likely to cause any obscure problems? Also hints on restoring the networking in the RTAI kernel would be appreciated. The system thinks the ethernet connector is unplugged but it's clearly not, as the networking works fine upon rebooting into the standard 3.13 kernel.

I have no experience with Ubuntu Precise, but RTAI and networking are not necessarily mutually exclusive. Networking works fine on my Ubuntu Lucid installs, and Debian Wheezy and Debian Buster (with RTAI) without any special effort. No idea what could be causing it to fail on your system.