Introduction to Docker

Given at the first Chicago Docker meetup

1. John Downey | @jtdowney
4. Laptop CI QA Staging Prod Rails code ? ? ? ? ? PostgreSQL ? ? ? ? ? RabbitMQ ? ? ? ? ? libxyz ? ? ? ? ?
5. http://www.flickr.com/photos/neonman/1438473495/
6. LXC Linux Containers
7. LXC: LINUX CONTAINERS • Linux host (kernel >= 2.6.29) • Linux container (guest) • Must match host architecture • No need to match kernel/distro
8. DOCKER • Builds on LXC • Server (host) mode requires Linux and LXC • Recommend kernel >= 3.8 • Client mode runs almost anywhere (Linux/OS X)
9. WHAT DOCKER ADDS • Images • Layers • Tags • Repository • Create and share images
10. DOCKER COMMAND • Written in Go • Open source • Manages containers and images • Provides HTTP API • Built in CLI client uses API
11. ADVANTAGES OVER A VM • Package a run-time environment • Runnable on any linux host • Keeps things isolated and ephemeral • Fast and simple
12. IMAGES
13. IMAGES VS CONTAINERS • Images are a template • File system • Metadata (ports to expose, command to run) • Containers are what is running
14. IMAGE LAYERS • Images are built up from layers • Each layer is read-only filesystem • Top layer is a new read-write layer
16. IMAGE HIERARCHY • Form a directed tree • Each image can specify a parent image • Starts with the parents layers below its own
17. Ubuntu App A B C DB A B
18. WAYS TO MAKE IMAGES • Commit a running container (docker commit) • Dockerfile (docker build) • Import a tarball (docker import)
19. DOCKERFILE • FROM - What my parent image is • RUN - Perform a command to prepare the image • ADD - Add a file to the image • EXPOSE - Allow access to a specified port • ENV - Set an environment variable • CMD - Default command to run on container creation
20. FROM wheezy-base ! ENV DEBIAN_FRONTEND noninteractive ! RUN apt-get install -y ruby1.9.1 ruby1.9.1-dev RUN apt-get install -y build-essential RUN apt-get install -y libpq-dev RUN apt-get install -y libxml2-dev libxslt-dev RUN apt-get install -y libcurl4-openssl-dev RUN gem install bundler ! EXPOSE 3000 ! WORKDIR /gateway ADD . /gateway/ RUN bundle install ! CMD ["bundle", "exec", "rails", "server", "thin"]
21. REPOSITORY / INDEX