Which is why I think you should not try to build generic images like this. I looked at the source and it seems like s lot of work had been put into creating a f

Which is why I think you should not try to build generic images like this. I looked at the source and it seems like s lot of work had been put into creating a fragile mess. After having been burned several times by images I prefer writing my docker images from scratch (based on the Debian or Alpine images) for production systems. I only use ready-made images for quickly getting something running locally to evaluate it.