A couple of useful aliases for docker

Writing Dockerfiles is pretty funny experience. I like the idea of writing the minimum amount of instructions that will make it possible to run kafka, redis, influxdb or whatever. While taking my first steps in developing a Dockerfile I noticed I keep typing the same commands over and over. Since I’m a bit lazy I started looking into aliases other people were using to solve the same problem (being lazy also means you don’t want to re-invent the wheel). I think I found something that really fits my needs and it is done the way I would do it. However, I couldn’t find the reference anymore so I finished re-implementing the aliases on my own (that felt like re-inventing the wheel somehow) and I can’t give credit to the person that originated this idea.

The basic idea is adding aliases to docker in a way they feel like native commands. They look like:

docker clean

instead of following the usual alias foo=bar approach. In order to achieve the native feeling I implemented the following function:

docker() {
  if command -v "docker-$1" > /dev/null 2>&1; then
      subcommand=$1
      shift
      docker-$subcommand $@
  else
    /usr/local/bin/docker $@
  fi
}

The function is using its first argument to check if there is a command on the system that matches the argument itself using a convention that I have already seen in git (there is a nice stackoverflow discussion about how to check if a command exists here). Basically, if you want to add a docker clean command, you need to make an executable named docker-clean available in your path. If this command exists, it gets executed. Otherwise the function delegates the execution of the given command to docker. Pretty simple and pretty neat. So far I added two aliases for commands I’m executing all the time. I have a docker clean that looks like this:

#/bin/bash

docker rm $(docker ps -a -q)

Simple and effective. And then I have a docker sh that looks like this:

#/bin/bash

docker run -i -t --entrypoint=/bin/bash $1 --

Very helpful to look around in a container while building it.

The only thing I miss is auto-completion for my custom commands but I may add it soon. I hope it helps you simplify your workflows while building Dockerfiles.

See also