• OS-level virtualization (not simulating hw)
  
  
• Faster and smaller than VMS
  
  
• chroot on stereoids
  
  
• Many flavours around (OpenVZ, VServer, LXC)
  
  
• Docker currently supports LXC exclusively
  

 $ docker run -i -t ubuntu /bin/bash

• Development
  
  
• Testing
  
  
• Production

• Pull an image and go
  
  
• High dev/prod parity
  
  
• Isolated everyting
  
  
• Low resource consumption

• Isolated test environment
  
  
• System tests incl. backing services
  
  
• Run tests parallel if you want

• Container: State of a VM
  
  
• Images: Snaphots of containers
  
  
• Index/Registry: Repository of containers
  
  
• Dockerfile: Buildscript for images
  
  
• Layers: Stack of filesystems

# Start a new container$ docker run -i -t ubuntu:12.10 bash
# Do stuff
[c123]# apt-get update[c123]# apt-get install memcached[c123]# exit
# Save container as an image
$ docker commit -m "memcache" c123 username/image

FROM ubuntu
RUN apt-get update
RUN apt-get install -y memcached

$ docker build -t sr/memcached .$ docker run sr/memcached memcached -u root

• Just start a container and hack away
  (Don't tinker with Dockerfiles too long)
  
  
• Commit your container when it's ready
  
  
• Remember: containers are persistent
  
  
• Start with a minimal running version
  (Don't install nginx, db and such)
  
  
• Mount local volumes:
  

   $ docker run -v /host:/container ...

• Service discovery:
  
• No reliable connection to host or other containers
• Solution 1: dns-server & env vars
• Solution 2: etcd distributed key value store
• Solution 3: maestro docker orchestration
• ...

• Process monitoring:
• Only one process running in container when started
• Upstart doesn't work with custom scripts for me
  
• Solution 1: Create bash script to start everything
  
• Solution 2: Use supervisor / foreman / honcho etc.

 $ docker run guetux/feincms

$ docker login$ docker push guetux/feincms