As of today, brtmr.de is part of the letsencrypt.org closed beta. If you inspect the certificate by clicking on the little lock-symbol in the adress bar of your browser, you should see something like this:
The process was mostly painless - I just cloned the github repo, as explained in the official documentation:
git clone https://github.com/letsencrypt/letsencrypt cd letsencrypt
Afterwards, installation and configuration of the required packages can be run with the
One issue I was not previously not aware of is that the installation of the client is rather memory hungry. So if you are like me, and you are running your site on a tiny VPS, then you might run into a rather cryptic error message, like this. This problem can be fixed by creating a swapfile so that the installation process does not run out of memory, as pointed out in this github-issue.
After that, everything worked smoothly. I also enabled the rewrite option, so that apache rewrites every http connection into https.
My thanks to the people at letsencrypt for making this process easy and free, and providing an important step to hopefully making the web https-only.