Core PostgreSQL easily allows multiple servers to run on the same system, but there are a few wrinkles to be aware of.
Some installer versions create a PostgreSQL data directory named data. It then gets a little difficult to have more than one data directory without using different directory structures and names.
Debian/Ubuntu packagers chose a layout specifically designed to allow multiple servers, potentially running with different software release levels. You might remember this from the Locating the database server files recipe in Chapter 2, Exploring the Database.
Starting from /var/lib/postgresql, which is the home directory of the Postgres user, there is a subdirectory for each major version, for example, 8.4 or 9.3 ...