A brief introduction to docker, given locally to a few places/people

1. Docker
AKA “the last Vagrantfile you’ll ever need”*
* Disclaimer: probably not the last Vagrantfile you’ll ever need

2. What is Docker?
 http://docker.io/
 “Docker is an open-source project to easily create
lightweight, portable, self-sufficient containers from any
application.”
 Based on LXC (linux containers)
 From dotCloud
 Written in Go

3. …but what is it really?
 Dockerfile to define a starting point (eg. “Centos”) and a
set of instructions to prepare your environment and run
your application
 Image(s) containing all the defined environment and
your app
 Containers with running processes
 All self contained and isolated from the host
 Public registry of other people’s images

4. Why would I use it?
 Dev/prod/staging consistency
 Ability to streamline CI/CD

5. Performance
 Each container is simply a process, no other overheads
(simply isolated in the kernel).
 Run 10-100 containers on your laptop, each one self-
contained
 CPU == native, Memory == slightly higher, Network ==
_slightly_ slower
 Copy on write filesystem (AUFS or BTRFS)

6. Structure
 Encourages micro-services approach
 Every separate daemon should be it’s own container
 Discourages talking to localhost or making naive
assumptions about all services being locally accessible
 Has a “linking” system for exposing other container IP
and port details via environment variables
 Also encourages viewing services (containers) as
immutable

7.  Docker encourages a full CI/CD pipeline

8. Installation
 Trivial on modern linux (apt-get or yum install lxc-
docker)
 Near-trivial on OS X (install boot2docker, or dvm)
 Latest AWS images now support docker by default (as
does EBS)
 Various vagrant images available for vbox, vmware, etc

9. Example Dockerfile
FROM centos
MAINTAINER Kevin Littlejohn <kevin@littlejohn.id.au>
RUN echo 'NETWORKING=yes' > /etc/sysconfig/network
# Install Postgresql
RUN rpm -i http://yum.postgresql.org/9.3/redhat/rhel-6-x86_64/pgdg-redhat93-9.3-1.noarch.rpm
RUN yum install -y postgresql93-devel postgresql93 postgresql93-server postgresql93-contrib
ENV PATH /usr/pgsql-9.3/bin:$PATH
RUN service postgresql-9.3 initdb en_AU.UTF-8
ADD pg_hba.conf /var/lib/pgsql/9.3/data/pg_hba.conf
RUN service postgresql-9.3 start && chkconfig postgresql-9.3 on && su postgres -c "createuser –s postgres"
USER postgres
EXPOSE 5432
CMD ["/usr/pgsql-9.3/bin/postgres", "-D", "/var/lib/pgsql/9.3/data", "-i", "-h", "0.0.0.0"]

10. 12 Months of Docker
 Contributions from more than 400 developers;
 More than 1.4 million downloads;
 More than 10,000 Dockerized applications available in
Docker’s public index; and
 Accelerating community engagement, including more
than 77 Docker Meetup groups in 30 countries.

11. Add-ons
 Drone
 Shipyard
 Registry
 CoreOS
 Fig
 Maestro
 Continuously !

12. Integrations
 Packer
 Vagrant
 Jenkins (Docker build step and Docker plugin)
 Docker (DinD)
 Google AppEngine
 OpenStack

13. Systems Using Docker
 Travis-CI
 Blockade
 CoreOS
 Quay.io
 Orchard
 OpenShift

14. Other nice features
 Trusted images on index.docker.io
 Logs of exited containers
 Caching of images for repeat builds
 Docker daemon and REST API

15. Tips for Use
 Heavy use of Environment variables
 Look into fig, maestro, or coreos/fleet
 Never refer to localhost
 AUFS vs BTRFS