Keter is the Yesod’s deployment system, fully featured and a joy to use, but there are some pitfalls that the documentation doesn’t cover, and that the user has to find out for her self; So I’ll try to give them away here together with a walk-through tutorial.
Although Keter is flexible and general enough to be used with various kind of applications and web frameworks, here I’m going to assume you’re using it to deploy Yesod applications. Moreover, I’ll assume you’re using Yesod’s scaffolding, as it is the preferred way to write production ready applications.