I've just installed Ubuntu Server 12.04 on my spare box, and I'm using a command line interface only to get my feet a little wet. ping google.com does work, so I know my connection is up and running. At first, sudo apt-get update gave me a 404 error, so I followed this advice and added those lines to my sources.list file. While I no longer get the 404 error, I now get many errors like the following one:
Err mirror://mirrors.ubuntu.com precise-updates/restricted i386 packages
No mirror file '/var/lib/apt/mirrors/mirrors.ubuntu.com_mirrors.txt' found [Mirror:]
I get this error with /restricted, as in above, and also with /universe and /multiverse.
I also get this error with precise-updates, as in above, and also with precise-backports and precise-security. I suppose this makes sense, since this is everything that was added into sources.list, but I have no idea where to go from here since searching yields nothing, or if the problem is on my end or theirs.