Docker One Liners

If you want to install a specific set of software, you use a `Dockerfile` to create an `image`. If the `image` is already on docker hub, you don't need to write a Dockerfile.

Images are used to create containers, which are images that have started up. They could then be stopped and restarted if you need to, but they have long running state. Starting a container with `–rm` means that it cleans itself up after it ends, which is often what I want; go away after my attention wanders off.

Volumes – either docker managed or a directory exposed on the local file system – is a way for the storage that a container uses to be more durable. If you are running something "for real" you probably want to keep the data somewhere "outside" of the container so that if it goes away, or you update to a different image, you still have the data. I don't really use this feature.

My usage of Docker can either be to poke at a piece of software, play around with it for a bit longer, or use it more seriously. One gets a transient container that deletes on shutdown, the next gets a name and sticks around, and the final one has long term storage outside of the container.

In my projects I have a file called `LOCALSERVERS` that I run to make sure that the right containers are installed and started up when I start developing. The pattern is to create one if it doesn't exist, and then start it if it's not started. These containers are meant to stick around at least until I move on to other projects.

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if [ "$(docker container ls -a | grep pg-postgis | wc -l)" == "0" ]; then
    echo Creating pg-postgis container
    docker run --name pg-postgis -d -p 5432:5432 mdillon/postgis
fi

if [ "$(docker ps | grep pg-postgis | wc -l)" == "0" ]; then
    echo Starting pg-postgis container
    docker start pg-postgis
fi

When you have a bunch of interelated services, using docker-compose.yml is a great way to set things up. Especially if you have volumes to attach and keep around. It's worth mentioning that this is super useful, even if it doesn't fit into the 'one-liner' limitation.

Lets startup a postgres container that has postgis extensions installed:

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  docker run --name postgis -d -p 5432:5432 mdillon/postgis

Need a web interface to run SQL commands?

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docker run -p 4000:80 \
       --name pgadmin \
       -e 'PGADMIN_DEFAULT_EMAIL=wschenk@gmail.com' \
       -e 'PGADMIN_DEFAULT_PASSWORD=SuperSecret' \
       -d dpage/pgadmin4

Explore your built images:

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docker run --rm -it \
    -v /var/run/docker.sock:/var/run/docker.sock \
    wagoodman/dive:latest <image>

Easy temporary redis instance.

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docker run --rm -it redis

1. Installing Docker
2. mdillon/postgis
3. PgAdmin Container
4. Dive
5. Redis