The document provides an overview of Docker, an open platform for developing, shipping, and running applications using containers, which are lightweight virtualization technologies. It emphasizes the benefits of containers, such as speed and portability, and highlights Docker's role in fostering collaboration between development and operations teams. Additionally, it details how Docker images are built from layers and mentions resources for further information.

1. Docker
Charles Anderson
Hack Salem - November 2014

2. What is Docker?
• An open platform for developing,
shipping, and running applications
• Linux-based
• Why? Speed - ship code faster,
including test and deployment
• A solution to “works on my machine”
Not!

3. One Word: Containers!

4. Containers
• Containers are a lightweight
virtualization technology
• User-mode virtualization - not
hardware virtualization
• Benefits: density, speed, portability
• Not new, and Docker isn’t the first

5. Peace, Love and
Understanding
• Devs and ops working
together with a
common tool
• “The real value of
Docker is not
technology. It’s getting
people to agree on
something.” - Solomon
Hykes, CTO Docker

6. What’s a Container?
• An isolated environment to run user-mode code
• Looks like you have the OS to yourself
• An initial file system called an image
• Minimal - a lot less than a full Linux distro
• Very fast to start - less than a second
• Network connections

7. Images
• Start with a base - very minimal
• Add packages using usual tools - e.g. apt, yum
• Dockerfile is a recipe to build the image
• Not needed at run-time

8. Dockerfile
FROM ubuntu:12.10
RUN apt-get update && apt-get install -y redis-server
EXPOSE 6379
ENTRYPOINT ["/usr/bin/redis-server"]

9. Connections
• Open network ports to the outside world
• Connect ports between containers via a private
network
• Mount persistent storage - c.f. Amazon EBS

10. Zen of Containers
• Devs fill containers - with code
• Ops slings them around
• c.f. intermodal cargo containers

11. Collaboration
• Docker Hub provides a GitHub-like experience to
publish/share containers
• Traditional VMs hard to share
• Automated build from GH or BB
• Private DockerHub available
• Private, on-premise registry available (& free)

12. Cold Fusion and Unicorns?
• Image files are composed of layers -
one for each step in Dockerfile
• Each layer is actually an image
• Each layer is a diff from the previous
layer
• The top layer is read-write
• All done efficiently with union file system

13. No Neck Beard?
No Problem
• Boot2Docker runs on Mac and Windows to provide
development environment to run Docker
• VM running minimal Linux kernel and OS
• Same idea is useful in production - CoreOS

14. More Info
• Docker.io
• DockerBook.com
• Software Engineering Radio podcast - se-radio.net
• December 2014