To run Links programs that manipulate the database you need to install one of the following database engines on your system: MySQL, PostgreSQL, SQLite or MonetDB. Once you have done that you need to compile Links with at least one of these database backends enabled.

1. Install postgresql package using your package manager, eg. on Debian or Ubuntu this will be something like:

   apt-get install postgresql
   

   Once you've done that you need to configure the database by creating a new user and creating at least one database for that user. If you want to run the Links test suite you should create a database called links. Refer to PostgreSQL documentation for details.

2. Install OCaml bindings for PostgreSQL. This can be done using OPAM:

   opam install postgresql
   

   Note that these bindings require some extra development libraries installed on your system. OPAM will guide you in case these are missing.