How to install network drivers via terminal?

I have a PC with:

32GB RAM

1T harddisk

8 core cpu

ubuntu server 12.04

I installed virtualbox and created four VMs. I think my mistake was I didn't leave any space for the host so I got "The system is running in low-graphics mode" error. I tried to reinstall the OS but I keep getting the network configuration error during the installation. I figured out that the problem was with network driver so I tried to install it again using apt-get or via dvd but nothing worked..

To make sure that the problem is the network, I installed windows server and the network wasn't working too so i installed the driver and it worked!

So I need to know how to install ubuntu network drivers via terminal, coz I couldn't install GUI without network :(

Please help!!