Infrastructure
Docker from Scratch: Images, Containers, and Registries
What Docker actually is under the hood - from a Dockerfile to a running container, and where registries fit in.
Infrastructure
Linux for Developers Who Aren't Sysadmins
You don't need to be a sysadmin to be effective on Linux - you need to understand processes, file descriptors, permissions, and signals well enough to debug what goes wrong in production.