One surefire way to gauge the health of a software ecosystem: The amount of third-party work done on its behalf. If everyone and their brother (and cousins and neighbors) are diving in and producing, odds are it's going well. Case in point: Docker.
As the software containerization technology matures from a nifty idea to a useful tool, the accompanying cornucopia of third-party goodies has also matured. Here are four of the more useful prizes we've found in the Docker treasure chest of late.
Wsargent's Docker Cheat Sheet
Alternate title: Everything You Always Wanted to Know About Docker but Couldn't Find or Didn't Know How to Ask For. GitHub-hosted for easy pull-request additions, Wsargent's Docker Cheat Sheet is a succinct rundown of all aspects of Docker -- not only the command-line operations, but the instructions used in Dockerfiles, a quick inventory of common security tips, and some gotchas one might encounter in day-to-day work. Check back often, as it's updated regularly.
Docker's logo may feature a whale, but your Docker containers don't have to be similarly outsized. Docker-slim is "a magic diet pill for your containers" -- it lets you analyze a container image and prune superfluous items.
Your savings depend entirely on what you're culling, but dramatic changes are possible. A sample Python container went from around 433MB down to 15.97MB; a sample Java app went from 743MB to 100.3MB. The analysis can be performed apart from the actual reduction, so you can use the information gleaned to perform your own cleanup.
For another approach to the same basic idea, see also Skinnywhale.
Most Docker users work from the command line. A few might use a GUI like Kitematic, but most of the action is in the CLI. That's even more reason why a better CLI -- one better attuned to Docker behavior -- might be in order.
Wharfee tries to be exactly that: a shell that takes the repetition, puzzlement, and guesswork out of using Docker. Everything from Docker commands to the names of containers and running images can be autocompleted as you type, along with shortcuts for common behaviors like removing all dangling images. You could set up many of those shortcuts in your own shell, but the point of Wharfee is that you don't have to.
If you're averse to the idea of a container stuffed with anything more than it needs, Chaperone lets you start slender and stay slender. It provides a single process that can be bundled into a container for managing how services start, how processes are administered, how tasks within the container are scheduled (à la cron jobs), and many other little duties that are normally handled by systemd or another top-heavy service.
"If you are currently starting up your container services with bash scripts," reads the project's README file, "Chaperone is probably a much better choice."