[lug] Debian lifesaver

[Daniel Webb]

Just found out I upgraded Firefox from 1.5 to 2.0 a few days ago during an
upgrade, and now none of my extensions work!  So how to get back a previous
package if you flushed the apt packages cache?

deb http://snapshot.debian.net/archive/date/7-days-ago/debian testing main
	contrib non-free

Then downgrade the package to the old version using aptitude (or apt-get with
the version specifier), then set the package to "hold".  I never even knew
this existed, but man is it a lifesaver!