That's very true, although there is usually quite a lot more to configuring Chef, I can see that it can be done without too much complication using Dockerfiles.

That's very true, although there is usually quite a lot more to configuring Chef, I can see that it can be done without too much complication using Dockerfiles. I apologize for not mentioning this. I prefer Chef (or some other provisioners) as a special case because it is a common case. It is just software, but if all your servers (or a majority) are configured using Chef, its nice to have an abstraction to make this easy. The same argument could've been said for Vagrant early on, probably: I could've just supported shell scripts, because shell scripts could install Chef, then run Chef. Perhaps so, but having the "just set this one to handful of options and you get Chef for free" functionality was a big win for both Vagrant and Chef adoption (as well as other provisioners, I'm just using Chef as an example here). Likewise, I'm finding that having Docker as a special case in Packer/Vagrant is doing the same: it is educating more people about Docker with a low barrier and bringing more people into an ecosystem I like (VMs, containerization, immutability, or any mix there-in). I'm super excited about where Docker is headed, and glad containers are finally reaching a point where they're friendlier for laypeople (as in... not super experienced Linux sysadmins) can use them. :)