Docker

So in my last article I created a Docker container with nothing but a statically compiled helloworld in it. That demonstrated how it’s possible to define a very very (very very) simple container. Here I define a similarly simple container with more complex dependencies - a hello world perl script requiring the Modern::Perl perl module. Now I don’t even need to build the executable binary, but all of a sudden I need to include enough of an environment to support my simple perl script. As far as working with Docker this is not much more complex than changing “FROM scratch” to “FROM debian:latest”. The result is a much bigger container which will take more resources to run, but other than providing the computing resources to support that I really don’t have to care about it that much. The Dockerfile now looks like this: ...

Docker is a framework which makes it easy to wrap linux applications in “containers” - a sort chroot’d jail but with tools to take away the pain of setting up dependencies and also providing tools to help automate setting up dependencies between those containers. The Docker Hub provides a bunch of pre-defined containers from major projects like Ubuntu, mysql, Redis, nginx, wordpress, postgres and java. It’s also a central store (like github, but for Docker) of publicly created and licensed Docker containers. What’s the simplest quickest way to start? Well there is a special base container called SCRATCH, which is used in the Docker official hello world container. A container based on SCRATCH has nothing in it, so whatever you add has to be fully self sufficient. The Docker official hello world does this with some assembly code compiled by nasm which certainly covers the angle of a stand-alone executable but I think is arguably more complex than a statically compiled hello world - so here we go: ...