I’ve been making a lot of use of PostgreSQL and PostGIS for working with geo-data over the past year and, having finally gotten over my hatred of the non-standard administrative commands, I am seriously impressed with what this setup makes possible. Even on a MacBook Air with just 8GB of RAM! However, one area where I’ve run into problems is the use of extensions on OS X so this post is intended as a handy reference for how to install them.