• Build image from Dockerfile

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• In CICD, Jenkins takes the github repo to perform actions
• At last, it takes the Dockerfile to create the docker image and push it to Container Repository
• Dockerfile is like a blueprint to build images
  • available docker file commands - FROM, ENV, RUN etc
  • always called Dockerfile

    # start with a base images
    FROM node
    # set env variables
    ENV MONGO_DB_USERNAME=admin \
    MONGO_DB_PWD=password
    # RUN command executes inside the container
    # so directory is created inside of container
    # RUN <any linux commands>
    RUN mkdir -p /home/app
    # COPY executes on the HOST machine
    # COPY source on host -> target on container
    COPY . /home/app
    ENTRYPOINT ["docker-entrypoint.sh"]
    # CMD is entry point command
    # as server.js copied to /home/app folder
    CMD["node", "/home/app/server.js"]
    # this is equivalent of `node server.js` on local host machine
    

CMD vs RUN in Dockerfile

• you can have multiple RUN commands
• but only 1 CMD command as entrypoint command

Build image from Dockerfile

# -t app-name and tag
docker build -t my-app:1.0 .
# . => same dir has Dockerfile

docker ps -a | grep my-app
# filter containers having my-app

• every time you change Dockerfile, you need to run docker build command.