Docker knowledge to get you through the day

Mar 15, 2021 · 6 min read

Following on from the “Git commands to get you through the day” post, Paddy Morgan and I delivered a Docker 101 workshop today at work.

This post covers what we ran through.

Time allocation: 60 minutes

This workshop will be a high level overview of the basic docker commands you will use daily. It’s an entry level workshop, so if you’re comfortable with docker on the CLI, this probably isn’t for you.

What we will cover:

Some up front terminology


We need to make sure we have docker installed, so let’s run that first.


If Docker is installed, this will output a raft of commands that we can make use of. If you haven’t got Docker, checkout the installation page.

You may notice that some of the commands are the same, e.g.

Take some time to review the output from the main docker command.


Let’s start with understanding what images we have on our machine.

docker images

This shows us all the images that are pre-built and stored on your machine. Any images listed here are available to be run locally. If you have not used Docker before, the list is likely to be empty.

Let’s pull down the hello-world image.

docker pull hello-world

If you now run docker images you should see something very similar to this:

❯ docker images
hello-world     latest    d1165f221234   7 days ago     13.3kB

Running basic commands

Let’s now run that image as a container.

docker run hello-world

So docker is the main command. run is the subcommand which allows us to run the hello-world image as a container.

If we now run docker ps -a you will see containers that are: running, have ran and stopped.

❯ docker ps -a
CONTAINER ID   IMAGE         COMMAND    CREATED              STATUS                          PORTS     NAMES
1fd4a9f1b80b   hello-world   "/hello"   About a minute ago   Exited (0) About a minute ago             practical_blackwell

Ideally, we want to clean-up after ourselves. So lets run the container again.

docker run --rm hello-world

Notice the --rm flag, which will remove the container once execution has finished.

If we run docker ps -a again you will notice there isn’t a new entry in the list.


Let’s cover two scenarios

  1. An environment you want to work in.
  2. Shipping something.


Let’s look at a VS Code Dev Environment.

Key items to cover off are:

Shipping something

Let’s look at Hagen which is a CLI tool for getting some data out of GitHub. This is running a Go binary inside the container.

Key items to cover off are:


Let’s look at the Hagen example again.

docker build -t benmatselby/hagen .

Breaking this down we have docker build as the command.

-t defines the string we will tag the image with. You can specify multiple tags, and they will all show when you run docker images.

And finally the . provides the context to the build command.

Running more advanced commands

For a more in-depth review of what you can do whilst running containers, please see the documentation.

An example of sharing environment variables, and files from the host to the container.

docker run \
  --rm \
  -t \
  -v "${HOME}/.benmatselby":/root/.benmatselby \

Breaking this down.

What if you want to get your terminal back, and run the container unsupervised? Then you can do this

$ docker run \
  --rm \
  -p 8080:80 \
  -v "$(pwd):/usr/share/nginx/html" \
  -d \
$ curl http://localhost:8080/

The extra bits here are:

Process management

Want to know what processes are running?

docker ps will give the current containers running.

docker ps -a will give you all the containers that are running and stopped.

Want to connect to a container that is running, then you can do this:

docker exec -it dcc55061e1118f7b6ccf2c3708d717531bf0c92327ed42f94f08d13020e901ea bash

Breaking this down, we have docker exec for executing something, but we run interactively with -it options and then run bash. This could be zsh or actually any command that is available in the container. Notice we are using the same container from the nginx example.

Want to know more about a running container, then run

docker inspect dcc55061e1118f7b6ccf2c3708d717531bf0c92327ed42f94f08d13020e901ea

To stop a container you can run

docker stop dcc55061e1118f7b6ccf2c3708d717531bf0c92327ed42f94f08d13020e901ea


These commands will help keep your machine tidy:


docker system prune


See also