So I applied for a job that had experience with linux operating systyems listed as a requierment, and since I did use Ubuntu for a while I said I did have some experience but it turns out they want someone who knows how to work with Linux servers, I have basically no knowledge of servers, other than that they are used to host webpages and such so was wondering if anyone could point me to some good resources for learning about this stuff in case I get a call back from these people.