$ sudo apt-get update
$ sudo apt-get install rt4-db-postgresql 

rt4-db-postgresql is installed in your system.

Make ensure the rt4-db-postgresql package were installed using the commands given below,

$ sudo dpkg-query -l | grep rt4-db-postgresql *

You will get with rt4-db-postgresql package name, version, architecture and description in a table

rt4-db-postgresql package basic information: