CONTINUAL INTEGRATION

Problem scenario
You want to create your own Dockerfile. You also want to invoke reserved words such as FROM, RUN, COPY, WORKDIR, ADD, and LABEL. You want to then create a Docker image from it. You want to ultimately create a working Docker container from that image. How do you do all of this?

Solution

1. In a given directory, create a file called extra.txt. It can have nothing in it and be created with a "touch" command.

2. In this directory create a file calle hello.py with this as its content:

from flask import Flask
app = Flask(__name__)

@app.route('/hi')
def hello_world():
    return 'Hello World!'

if __name__ == '__main__':
    app.run(host='0.0.0.0', port=5000)

3. In this directory create a file called Dockerfile with the content below:

FROM ubuntu:latest

LABEL Remarks="www.continualintegration.com created this Dockerfile"

RUN apt-get update
RUN apt-get install -y python3 python-pip
RUN apt-get clean all

RUN pip install flask

ADD hello.py /tmp/hello.py
# This stanza expects a hello.py file to be in the same directory as the Dockerfile itself.

COPY extra.txt /tmp/extra.txt
# This stanza expects an extra.txt file to be in the same directory as the Dockerfile itself.

EXPOSE 5000

ENV HOME /home/   
# This stanza will set Docker container's home directory in container's env settings 

WORKDIR /tmp/  
# The default directory when you enter the container will be the directory set above

CMD ["python","/tmp/hello.py"]

4. Run this command (but replace "foobar" and "contint" as you see fit):

docker build -t foobar:contint .

5. Replace abcd1234 below with the alphanumeric value that was displayed (associated with the newly created image ID):

docker create -it abcd1234 bash

# Run the above command with the substituted abcd1234 / container ID.

6. The above command should produce a new container. The container ID should be displayed. Run this command, but substituted wxyz6789 with the container ID you just created:

docker start wxyz6789

7. Run this command, but substitute wxyz6789 with the container ID you just started:

docker exec -it wxyz6789 bash