There is a lot of misleading marketing hype, misunderstanding, and plain misinformation about how containers/Docker make updates, and in particular security updates, easier, when the opposite is the reality. A lot of people buy into the CoreOS marketing hype, as though it was the only Linux distribution to offer automatic security updates. If you use containers as recommended, in fact the only thing CoreOS gives you are kernel updates, which is less than what other distributions provide. To get userland updates with Docker, you have to update your base image, then rebuild and re-deploy your application image, for every single application that you have. Or use custom kludge layers for updates:
https://github.com/SUSE/zypper-docker https://github.com/projectatomic/rpm-ostreeMaking maintenance and updates harder is definitely a container specific problem.