How to install Postgres on LINUX with two verions?

Question

I want to upgrade my postgres8.3 to 8.4 for single domain. Don't affect other domain. How to manage it. Is it possible?

Answer 1

It is possible... but not easy in all cases. In most distributions, it will be hard to install both of them using the package manager (because they will both provide the same capabilities). Supposing 8.3 has been installed using the package manager, you have to install 8.4 manually (using directly the archives you'll find on the official site).

The important step I can directly see :

• Install it in a logical place - respect the Unix architecture as far as possible.
• You have to create a dedicated script to declare it as a service. You certainly can use the one for 8.3 as a base. It will be in /etc/init.d, and you'll have to create the good links to be sure the service automatically starts on boot
• You have to be sure there are not any conflict between the thwo DB configurations. Particularly, be sure you don't listen on the same port. And be sure to declare the good port in the good configuration...
• You have to be sure that you don't erase the former binaries, those in /bin (or /usr/bin, or wherever they arae) that will let you manage your database. I don't know how freely you can use them with two databases installed.

Hope it will help you.

Answer 2

Assuming you're compiling from source, no problem. Set an appropriate prefix and data dir during the configure step, and you're good to go. If you're relying on your system's package manager, that's probably not going to work. If you're doing this as a migration process from 8.3 to 8.4, it'll be cleaner to take a reliable backup and then upgrade in place; if that's what you're doing, consider the forthcoming 9.x branch of postgres.