At the moment this is a quick and dirty built, but it works. If I find the time I will make it a litte more "solid"
You can build the docker image with the command:
docker build -t 5_2_0/nagiosxi .
You can start the container with the command:
docker run -d -p 80:80 -p 5666:5666 -p 5667:5667 --name nagiosxi 5_2_0/nagiosxi
Afterwards you can access the console at:
http://YOUR_IP/nagiosxi/
Finish the installation wizard and enjoy!
You can safelly ignore the "SSH" error and "ntpd" warning in Nagios. it's normal because the container doesn't have SSH enabled. Also ntpd can 't run, because it cannot change the system time.
For licensing, change to "free license" to keep using the product. The free license implice a 7 host limit.