Docker

Useful concepts and snippets for using Docker

Guidelines

• Always add .dockerignore file.

• Try to use and exploit multi-stage builds.

Recipes

Installing Docker

sudo apt-get update
curl -sSL https://get.docker.com/ | sh
sudo usermod -aG docker $USER
sudo service docker start

Installing Docker-compose

sudo curl -L "https://github.com/docker/compose/releases/download/1.26.2/docker-compose-$(uname -s)-$(uname -m)" -o /usr/local/bin/docker-compose
sudo chmod +x /usr/local/bin/docker-compose
sudo ln -s /usr/local/bin/docker-compose /usr/bin/docker-compose
docker-compose --version

Dockerfile With python venv's

FROM python:3.8-slim-buster

ENV VIRTUAL_ENV=/opt/venv
RUN python3 -m venv $VIRTUAL_ENV
ENV PATH="$VIRTUAL_ENV/bin:$PATH"

# Install dependencies:
COPY requirements.txt .
RUN pip install -r requirements.txt

# Run the application:
COPY myapp.py .
CMD ["python", "myapp.py"]

Remove all exited containers: docker rm $(docker ps -a -f status=exited -q)

Building docker images:

• https://codefresh.io/docker-tutorial/build-docker-image-dockerfiles/

Remove all images docker rmi $(docker images -a -q)

Remove dangling images

docker image prune

Remove dangling volume

docker volume prune

Kill all system garbage

docker system prune

Run container

docker run --network="host" -p 8080:8080 --name <name-of-the-container> wilmerags/image-name:tag
# network host to make it visible

**Add parameters to docker image build **

docker build --build-arg APP_ENV=DESIRED_ENV -f Dockerfile -t wilmerags/twitter-executor:IMAGE_TAG .

# ...
COPY env/${APP_ENV}/.env /app/
# ...

Tag image for pushing

docker tag 434eb3701cc9 wilmerags/twitter-executor # 434.. is the image ID

Building local image into docker-compose:

• https://stackoverflow.com/questions/46032392/docker-compose-does-not-allow-to-use-local-images

Resources

• https://pythonspeed.com/articles/multi-stage-docker-python/

• https://medium.com/capital-one-tech/multi-stage-builds-and-dockerfile-b5866d9e2f84

• https://pythonspeed.com/docker/

• The Rabbit Hole of Using Docker in Automated Tests

• Bridget Kromhout has a useful blog post on running Docker in production at Dramafever.

• There's also a best practices blog post from Lyst.

• Building a Development Environment With Docker

• Discourse in a Docker Container