Docker: An Introduction

A brief overview of how to set Docker up as a viable alternative to a WAMP installation

Transcript

1. DOCKER: AN INTRODUCTION Andrew Millington / a.j.millington@abdn.ac.uk
2. A SMALL HISTORY LESSON Explosion of popularity for virtualisation in server rooms around 2008 Vagrant created as a way to maintain virtual machines
3. VAGRANT: THE GOOD Single interface to create, download, maintain, destroy virtual machines vagrant init - requires a Vagrantfile vagrant up vagrant ssh vagrant destroy Wrapper around existing mature technology e.g. VirtualBox VAGRANT: THE BAD Spinning up one, two, three or four machines inside your computer is expensive
4. CONTAINERS TO THE RESCUE Containers are not new chroot introduced in 1982 Change the root directory of a process so it doesn't see anything outside
5. CHROOT EXPLAINED Problem as need two copies of bin/bash
6. LXC OR LINUX CONTAINERS Chroot alone can only restrict access to files. What if we could restrict access to computer resources such as processes or memory? FreeBSD had BSD Jail Solaris launched Solaris Zones in 2004 Linux created LXC in 2008 with Parallels, Google and IBM among others Windows integrated a Linux layer 2016
7. NOT PERFECT Containerisation needed to address quotas and security concerns Not easy to use Not widely adopted
8. INTRODUCING DOCKER
10. A BRIEF DOCKER HISTORY
11. dotCloud, a hosting company, released Docker in 2013 Did for containers what Vagrant did for VMs Consists of a client and server
13. WHY SHOULD I CARE? Useful for developers as environment is identical Vagrant provisions box on first boot. Can cause issues... Small containers running single processes Development environment becomes modular
14. DOWNLOAD DOCKER FOR WINDOWS Two options available Docker Toolbox Docker Native Recommend to use Docker Toolbox for the timebeing
15. DOCKER TOOLBOX A suite of tools for running Docker in Windows or Mac OSX Docker Engine Compose Machine Kitematic
16. RUNNING OUR FIRST CONTAINER Open up the Docker Quickstart Terminal and write the following command docker run ­ti ­­rm ubuntu /bin/bash A command terminal will be opened for us within our Ubuntu container
17. DOCKERHUB
18. CREATING A DOCKER CONTAINER Try to run only one process per container. For our development environment we need: Apache and PHP MariaDB Will add Node.js and Redis at a later date
19. CREATING A DOCKER CONTAINER First we must create a simple Dockerfile for our Apache container # Version: 0.0.1 FROM: centos:7 MAINTAINER: Andrew Millington "a.j.millington@abdn.ac.uk" RUN yum update ­y && yum install httpd ­y RUN yum install php EXPOSE 80 Each instruction adds a new layer to the container and commits it
20. HOW A CONTAINER IMAGE IS CREATED 1. Docker runs container from image 2. Instruction executes making change to container 3. Docker commit runs to commit new layer 4. Docker runs a new container from this image 5. Next instruction executes. Process repeats
21. BUILD THE DOCKER IMAGE docker build ­t="sephster/docker­php56" . To view the image you just created use the docker images command
22. RUN OUR FIRST CONTAINER docker run ­d ­p 80:80 ­­name "php56" sephster/docker­php56 Note that we still have to expose our port when running the container. docker ps
23. MARIADB CONTAINER docker run ­­name mariadb ­e MYSQL_ROOT_PASSWORD=my­secret­pw ­d mariadb:5.5 That is all there is to it! ...not quite
24. GET OUR CONTAINERS TO COMMUNICATE docker run ­­name mariadb ­e MYSQL_ROOT_PASSWORD=my­secret­pw ­­link php56: Now we have a fully functioning web server we can access at http://192.168.99.1/ (usually)
25. OTHER USEFUL DOCKERFILE COMMANDS CMD - The command to run when the docker container is launched ENTRYPOINT - Pass arguments to the command specified in ENTRYPOINT ENTRYPOINT ["usr/sbin/nginx"] docker run ­p 80:80 ­­name nginx nginx ­g "daemon off;"
26. OTHER USEFUL DOCKERFILE COMMANDS WORKDIR - Set the working directory of the process ENV - Set an environment variable during the build process ENV MYSQL_ROOT_PASSWORD my­secret­pw RUN mysqld Please check the Docker website for further examples
27. GETTING OUR FILES INSIDE OUR CONTAINER docker exec ­ti php56 /bin/bash Problem: We will lose all our changes as soon as the container is deleted
28. DOCKER R/W MODEL
29. SOLUTION: VOLUMES Can be shared and reused between containers Container doesn't have to be running to share volumes Changes to a volume are made directly Changes to a volume will not be included when you update an image Volumes persist until no container uses them # Create a mount point to any container created from the image VOLUME ["opt/project"]
30. MOUNTING A HOST DIRECTORY AS A VOLUME It would be good if we could get our Mercurial/Git files on our host machine to be hosted within our container. Docker makes this easy. docker run ­d ­p 80:80 ­­name "php56" ­v C:/Users/s03am2/Documents/Mercurial_
31. SHARING IMAGES ON DOCKERHUB docker login docker push sephster/docker­php56 Dockerhub also allows you to set up commit hooks for automatic builds
32. STOPPING AND DELETING CONTAINERS AND IMAGES docker stop php56 docker rmi sephster/docker­php56
33. CONTAINER ORCHESTRATION
34. USEFUL DOCKER-COMPOSE COMMANDS docker-compose up Builds, [re]creates, starts and attaches containers docker-compose start Starts existing containers docker-compose stop Stops running containers
35. OUR DOCKER COMPOSE FILE
36. OUR DOCKER COMPOSE FILE
37. OUR DOCKER COMPOSE FILE