Running multiple PostgreSQL servers on one physical system is possible if this is more convenient for your needs.
Make sure you've read the recipe Deciding on a design for multi-tenancy, so that you're certain this is the route you wish to take. Other options exist, and it is possible they may be preferable in some cases.
Core PostgreSQL easily allows multiple servers running on the same system. There are a few wrinkles of which to be aware.
Some installer versions create a PostgreSQL data directory named "data". It then gets a little difficult to have more than one data directory without different directory structures and names.
The Debian/Ubuntu layout is specifically designed to ...