Docker Workshop

The Workshop is separated in three sections

• CLI Basics
• Dockerfile basics
• Docker Patterns

Preparations:

• Install Docker
• Clone this repo: git clone https://github.com/harbur/docker-workshop (Some code examples require files located here)
• Warm-up the images:

docker pull ubuntu
docker pull nginx

Assumptions:

• During workshop the following ports are used 4000-4010. If they are not available on your machine, adjust the CLI commands accordingly.

CLI Basics

Version

Check you have latest version of docker installed:

docker version

• If you don't have docker installed, check here
• If you're not on the latest version, it will prompt you to update
• If you're not on docker group you might need to prefix commands with sudo. See here for details about it.

Commands

Check the available docker commands

docker

• Whenever you don't remember a command, just type docker
• For more info, type docker help COMMAND (e.g. docker help run)

RUN a "Hello World" container

docker run ubuntu echo "Hello World"

• If the Image is not cached, it pulls it automatically
• It prints Hello World and exits

RUN an interactive Container

docker run -it ubuntu bash
  cat /etc/os-release

• -i: Keep stdin open even if not attached
• -t: Allocate a pseudo-tty

RUN a Container with pipeline

cat /etc/resolv.conf | docker run -i ubuntu wc -l

SEARCH a Container

docker search -s 10 nginx

• -s: Only displays with at least x stars

RUN a Container and expose a Port

docker run -d -p 4000:80 nginx
google-chrome localhost:4000

• -d: Detached mode: Run container in the background, print new container id
• -p: Publish a container's port to the host (format: hostPort:containerPort)
• For more info about the container, see nginx

RUN a Container with a Volume

docker run -d -p 4001:80 -v $(pwd)/hello-world/site/:/usr/local/nginx/html:ro nginx
google-chrome localhost:4001

• -d: Bind mount a volume (e.g., from the host: -v /host:/container, from docker: -v /container)
• The volume is linked inside the container. Any external changes are visible directly inside the container.
• This example breaks the immutability of the container, good for debuging, not recommended for production (Volumes should be used for data, not code)

Workshop 1 (10 mins)

• Build a static website
• Run it on your machine
• Share your (non-localhost) url on Chat room

Dockerfile Basics

BUILD a Git Client Container

Create a Git Container manually:

docker run -it --name git ubuntu bash
  apt-get update
  apt-get -y install git
  git version
  exit
docker commit git docker-git
docker rm git
docker run --rm -it docker-git git version
docker rmi docker-git

• --name: Assign a name to the container
• commit: Create a new image from a container's changes
• rm: Remove one or more containers
• rmi: Remove one or more images
• --rm: Automatically remove the container when it exits

Create a Git Container with Dockerfile:

cd docker-git
docker build -t docker-git .
docker run -it docker-git git version

• build: Build an image from a Dockerfile

docker-git/Dockerfile

FROM ubuntu:14.04
RUN apt-get update
ENV DEBIAN_FRONTEND=noninteractive
RUN apt-get -qqy install git

• The FROM instruction sets the Base Image for subsequent instructions
• The RUN instruction will execute any commands in a new layer on top of the current image and commit the results
• The ENV instruction sets the environment variable to the value

BUILD an Apache Server Container

Create an Apache Server Container with Dockerfile:

cd docker-apache2
docker build -t docker-apache2 .
docker run -d -p 4003:80 docker-apache2
google-chrome localhost:4003

docker-apache2/Dockerfile

FROM ubuntu:14.04
RUN apt-get update
RUN DEBIAN_FRONTEND=noninteractive apt-get -qqy install apache2
EXPOSE 80
CMD apachectl start; tail -f /var/log/apache2/access.log

• The EXPOSE instructions informs Docker that the container will listen on the specified network ports at runtime
• The CMD instruction sets the command to be executed when running the image
• The tail -f /var/log/apache2/access.log is to avoid that the docker container is shutted down aftee the CMD is executed

BUILD a Static website Image

cd hello-world
docker build -t hello-world .
docker run -d --name hello -P hello-world
google-chrome $(docker port hello 80)

• -P: Publish all exposed ports to the host interfaces
• port: Lookup the public-facing port that is NAT-ed to PRIVATE_PORT

hello-world/Dockerfile

FROM nginx:1.7.1
ADD site /usr/local/nginx/html

• The ADD instruction will copy new files from and add them to the container's filesystem at path

Workshop 2 (10 mins)

• Build your website with Dockerfile
• Run an instance
• Share your (non-localhost) url on Chat room

PUSH Image to a Registry

REGISTRY=localhost:5000
docker tag hello-world $REGISTRY/spiddy/hello-world
docker push $REGISTRY/spiddy/hello-world

• tag: Tag an image into a repository
• push: Push an image or a repository to a Docker registry server

Workshop 3 (10 mins)

• Push your website to the local Registry (use your github username)
• Push your website image
• Share your image name on Chat room

PULL Image from a Repository

docker pull $REGISTRY/spiddy/hello-world
docker run -d -P --name=registry-hello $REGISTRY/spiddy/hello-world
google-chrome $(docker port registry-hello 80)

• pull: Pull an image or a repository from a Docker registry server

Docker Patterns

Linking Containers Together

docker run --rm --name redis dockerfile/redis
docker run -it --rm --link redis:server dockerfile/redis bash -c 'redis-cli -h $SERVER_PORT_6379_TCP_ADDR'
docker run -it --rm --link redis:redis relateiq/redis-cli
  set hello world
  get hello

Ambassador Pattern

host A (Server):

docker run -d --name redis dockerfile/redis
docker run -d --link redis:redis --name redis_ambassador -p 6379:6379 svendowideit/ambassador

host B (Client):

docker run -d --name redis_ambassador --expose 6379 -e REDIS_PORT_6379_TCP=tcp://188.226.255.31:6379 svendowideit/ambassador
docker run -i -t --rm --link redis_ambassador:redis relateiq/redis-cli
  set hello there
  get hello

Data Volume Pattern

docker run -d -p 4004:80 --name web -v /usr/local/nginx/html nginx
google-chrome localhost:4004
docker run --rm -it --volumes-from web ubuntu bash
  vi /usr/local/nginx/html/index.php

Service Discovery Pattern

sudo vi /etc/default/docker
sudo service docker restart
docker run -d -p 172.17.42.1:53:53/udp --name skydns crosbymichael/skydns -nameserver 8.8.8.8:53 -domain docker
docker run -d -v /var/run/docker.sock:/docker.sock --name skydock crosbymichael/skydock -ttl 30 -environment dev -s /docker.sock -domain docker -name skydns

• Redis Service

docker run -d --name redis1 crosbymichael/redis
docker run -d --name redis2 crosbymichael/redis
docker run -d --name redis3 crosbymichael/redis
docker run -t -i crosbymichael/redis-cli -h redis.dev.docker
  set hello world
  get hello

• Service discovery with DNS:

dig @172.17.42.1 +short redis1.redis.dev.docker
dig @172.17.42.1 +short redis.dev.docker

• Load Balancing with DNS

docker rm -f redis1
get hello
dig @172.17.42.1 +short redis.dev.docker

Helper Methods

Cleanup Stopped Containers:

docker rm $(docker ps -q -a)

Cleanup Untagged Images:

docker rmi $(docker images | grep "^<none>" | awk '{print $3}')

Credits

This workshop was prepared by harbur.io, under MIT License. Feel free to fork and improve.