Bare metal doesn't mean what it used to.
Nowadays it is fashionable to deploy applications consisting of hundreds of files in a complex structure, but this is fashion and not technology and that's easy to demonstrate: in the old days, a C application consisted of hundreds of files in a complex structure, that would compile into one self-contained executable. There's no technical reason you couldn't take a RoR app (for example) and "compile" it and manage it just like any other process. Start it, stop it, move it around, one binary executable and one plain text file for configuration, that's really all you need for any application. Really.
I look at things like Docker and think, you are solving a completely artificial problem, and as soon as fashion swings the other way (10 years at most) people will wonder why people ever did this.
And that's what Docker is built on: processes + namespaces to restrict what each process group can access.
> I look at things like Docker and think, you are solving a completely artificial problem, and as soon as fashion swings the other way (10 years at most) people will wonder why people ever did this.
Things like Docker will still have value with single-executable containers. Problems that people have had for years. Even with single-executables.
You still need to manage privileges. You still need service discovery. You still need to manage the network. You still need to manage data volumes. You still need to manage the environment.
Docker provides mechanisms that either solves all of that, or provides information for tools to hook into (e.g. ability to query what ports the currently running containers expose).
I agree with you that there is distinct benefit in self-contained executables, and I think you'll find a lot of people working with Docker thinks the same. Partly this is part of what Docker gives us: We get to treat a bigger hairball of an environment pretty much like a single entity, even if we're not able to slim it down.
But partly, note that a lot of the adoption of Go within devops tools appears to at least partially be motivated by the simplicity of distribution and installation from getting static binaries (without having to use C). I prefer Ruby, and find Go to be a ugly, too low level, language, but I definitively understand the appeal Go has when it comes to simplicity.
Yet despite having those devops tools as single executables, people want to put them in containers to manage them properly.
If anything, I hope and think that things will move even further down this route. For my part, I'm containerising my desktop environment part by part. There's no reason we should not move to far more locked down process environments.
1. Docker appears to only allow a single entry point per container. What do I do if I want to run a container consisting of say postfix and dovecot together? If this is possible can someone please point me at it.
2. Go doesn't allow you to bundle resources with the executables (as say Java/C#) so you have to rely on 3rd party libraries to do this that aren't very good. I can't easily ship my templates with my web server for example as part of the "go build" process. Again if I'm wrong, please point me at a solution.
But if you absolutely want to put them in the same container, the solution is to run a process manager as the entrypoint. E.g. base it on something like baseimage-docker [1]
Re: 2. I don't use Go, so I can't answer that part.
Been trying to build a canned mail server for a few years so this is probably a nice solution if I can get my head around it.
Docker configuration files are standardised. Application configuration files generally aren't.
I still have no idea how TFA is using it.