Docker Workshop

This repo contains three sample projects for the docker workshop I ran on 14th of October, 2019. The slides used for the workshop are here.

Hello World!

Check if docker is working.

docker run hello-world

• This pulls down the hello-world image from docker hub.
• Then it creates & runs a new container, based on that image.

Run an Ubuntu Container

1. Pull the latest ubuntu image.

docker pull ubuntu:latest

2. Run a instance of the ubuntu image (ie. the container).

docker run -it --name ubuntu-container ubuntu 

3. Stop the container.

docker container stop ubuntu-container

3. Remove the container.

docker container rm ubuntu-container

5. Remove the image (optional).

docker image rm ubuntu:latest

Simple Python Container

This example shows you how to run python script in a docker container.

1. Build the image.

docker image build -t python-image ./python-app

2. Run the container, using the image we just built.

docker container run --name python-container python-image

3. Remove the container.

docker container rm python-container

5. Remove the image (optional).

docker image rm python:3

Simple Flask Container

We're now building ontop of the previous example. In this example we run a web server that just returns "Hello World!" when we visit http://localhost:5000

Flask is just a python library that allows us to run a web server.

1. Build the image.

docker image build -t flask-image ./flask-app

2. Run the container, using the image we just build.

docker container run -d -p 5000:5000 --name flask-container flask-image

• -d ~ run as a daemon process.
• -p HOST_PORT:CONTAINER_PORT ~ map host & container port

3. Stop the container.

docker container stop flask-container

4. Remove the container (perhaps so we can create it again??).

docker container rm flask-container

5. Remove the image (optional).

docker image rm flask-image

Flask + MongoDB Containers (Docker Compose)

0. Switch to the directory

cd flask-mongodb-app

1. Build the containers.

docker-compose build

2. Run the containers.

docker-compose up -d

3. Stop the containers.

docker-compose down

Misc

Dockerfile Instructions

INSTRUCTION (ARGUMENT)

• ADD copies the files from a source on the host into the container’s own filesystem at the set destination.
• RUN executes command(s) in a new layer and creates a new image.
• CMD sets default command and/or parameters, which can be overwritten from command line when docker container runs.
• ENTRYPOINT sets a default application to be used every time a container is created with the image.
• ENV sets environment variables.
• EXPOSE associates a specific port to enable networking between the container and the outside world.
• FROM defines the base image used to start the build process.
• MAINTAINER defines a full name and email address of the image creator.
• USER sets the UID (or username) which is to run the container.
• VOLUME is used to enable access from the container to a directory on the host machine.
• WORKDIR sets the path where the command, defined with CMD, is to be executed.
• LABEL allows you to add a label to your docker image.