ccwoolf / vagrant-docker-demo

Demo script

This demo script is intended to walk people new to Docker through running a container from Docker Hub, creating then running their own image, and finally using Docker Compose to automate the running of multiple containers.

Setup

1. Make sure that you have installed VirtualBox and Vagrant, then clone this repository using Git.
2. Open a terminal, cd to your cloned repository, then run vagrant up to start the virtual machine.
3. Wait a bit while the provisioner runs. It's installing Docker and some other things.
4. Run vagrant ssh to open an SSH session to the virtual machine.

Running an image

1. Start by running docker run alpine. You'll see Docker pulling in the image and it will then launch your container.
2. It ran - but it just kicked you straight out.
3. docker run -it alpine and have a look around. The -i and -t switches open an interactive session and allocate a TTY, allowing you to have a proper console session inside of the container.
4. Press CTRL+D to exit the container terminal and return to the virtual machine.

Building an image

1. First of all, cd /vagrant as that's where the Dockerfile is.
2. To build the container image, run docker build . - note the last dot: that's the build context which in this case is the current directory.
3. Docker will now build the container, doing what is defined in the Dockerfile.
4. Once it's built, docker image list reveals our image, but it's only referred to by hash.
5. Rebuild the image, but this time add a tag - run docker build --tag webapp ..
6. Notice that the build was much quicker - almost instant. This is because Docker is able to determine that nothing has changed and simply rebuilds the image using a cache.
7. Run docker image list again to show the image with a more usable name.

Running the webapp

1. With the image built, it can be run by executing docker run --name=webapp-container webapp.
2. Running that command will result in an attached session - you'll be able to see the container's stdout stream.
3. The server says it's listening! Browse to http://localhost:5000 to try and load the page.
4. It's likely that will result in a connection reset error. This is correct, as no ports are being forwarded to the container - the Docker daemon has no idea where to route this traffic.
5. Press CTRL+C to kill the container, then run docker run --name=webapp-container -p5000 webapp.
6. Try browsing to http://localhost:5000 again - you should see a web page now.
7. Kill the container and start it again. Notice how the ID has changed.

Docker compose

1. Make sure that any other containers are killed - run docker ps -a to list containers and docker rm -f $CONTAINER_NAME to remove them.
2. Run docker-compose up -d --scale webapp=4.
3. Browse to http://localhost and refresh. Nginx is load balancing your requests across four containers.