I need to use two different linux distros simulanously work some learning (network administration learning) purposes, I chose Ubuntu/Fedora or ubuntu/SUSE families. and decided to select a lightweight derivation of such of these three, for Ubuntu selected Lubuntu, But I do not know lightweight but complete distros that derived from the other two families. which you recommend. I have a two year old laptop (Core i5 cpu, 4G ram) and cannot dedicate lots of resources to virtual machines. I don't need X, and can (and prefer to) shut it down at first. I run Lubuntu (without X) with 128MB of RAM and it works fine.