Andrew Miotke

Posting about IT stuff. Sometimes programming, usually Python or Swift.

Expect this post to be updated over time.

Here are the notes I’ve taken so far while learning Docker over the last few days.

Resources

docker pull

Command:
  • docker pull [image name or url]

Pulls the docker image from the docker registry. The docker registry is similar to Github in that it hosts a bunch of docker images.

Use docker images to list all of the images on the local machine.

docker run

Command:

  • docker run [image name]

Flags

  • -d detaches the terminal window from the running docker container.
  • -P publishes all exposed ports to random ports so that the application inside the container can be accessed. You can also specify which port to use with docker run -p 8888:80 ....
  • --name gives the container a human readable name.

Runs a docker container based on the image that is passed in.

docker run -it [image name] attaches you to an interactive shell in the container itself.

docker stop

Command:

  • docker stop [container ID or name]

Stops the running container when running in detached mode.

docker ps

Command:

  • docker ps

Flags:

  • -ashows all containers that have been run.

Shows all of the containers that are currently running. Docker creates a new container everytime the command is run. That way the environment is always as you expect.

docker rm

Command:

  • docker rm [container ID]

Container stick around on the disk even after they are no longer running and have a STATUS of Exited. Run docker ps -a to get the container ID then run docker rm [container ID], i.e. docker rm 605982f999a1.

You can also pass in the --rm flag during the docker run command to delete the container after it’s been ran. i.e. docker run --rm busybox echo "Hello".

docker container prune will delete all exited containers at once. This way you don’t need to copy and paste each container ID in the docker rm command.

To get a list of containers use docker ps for active containers or docker ps -a for all containers that are currently running, exited, ect.

docker rmi

Command:

  • docker rmi [image name]

Deletes the docker image you no longer need.

To get the list of images use docker images.

Dockerfile

Dockerfile reference: https://docs.docker.com/engine/reference/builder/

A Dockerfile is a text file that outlines what a docker image should look like. It contains a list of commands that docker uses to build and create an image which can later be used to create a container.

Creating a Dockerfile by just creating a new file named Dockerfile.

Example Dockerfile I used from Docker for beginners

# Specify the base image first.
FROM python:3

# Set a working directory for our app
WORKDIR /usr/src/app

# Copy all the files to the container
COPY . .

# Install Python dependencies using the requirements.txt file
RUN pip install --no-cache-dir -r requirements.txt

# Expose the port that the app will run on
EXPOSE 5000

# Run the command for running the application
CMD ["python", "./app.py"]

docker build

Command:

  • Create a local docker imagedocker build [dockerhubUsername/image name] [location of Dockerfile]

Flags

  • -t to give the image a specific tag. Generally a version number.

docker build creates a docker image out of the Dockerfile. To add a tag the docker image use :[tag name] after the image name, docker build [dockerhubUsername/image name]:[tag name] [location of Dockerfile]

docker push

Command:

  • docker push [dockerhubUsername/image name]

Pushes the docker image to DockerHub.