The documentation was not up to date and the files mentioned are not included with mojoPortal. I've updated the article to show the contents of those files so you can create them. I think the error is just because the files don't exist on disk, with the updated article you could create them.
To be honest I'm no linux super guru myself. I generally prefer the gui tools, I would guess that Ubuntu has something available or you might try installing pgAdmin. I have pgsql running on a linux box but I connect to it from windows using pgAdmin to create and manage databases.
Or if you just want to play with mojoPortal you could try the Sqlite package for Mono since it has a zero configuration database. For a real production site pgsql would be a better choice.
Hope it helps,