How do I install older PostgreSQL (8.4) in Ubuntu 12.04?

Question

Well, it's the whole question. I installed 9.1 before, but I need older version now and I haven't yet found out how to do that.

Answer 1

If the old version of PostgreSQL is not available in Ubuntu repositories see PostgreSQL Apt Repository:

This repository will integrate with your normal systems and patch management, and provide automatic updates for all supported versions of PostgreSQL throughout the support lifetime of PostgreSQL.

Answer 2

sudo apt-get install postgresql-8.4 

Seems to do the trick (well, not really a trick).