A brief introduction to Docker presented at the Hack Salem! users group meeting in Salem, Oregon - November 2014

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