Introduction to Docker

Containerization is the new virtualization

who

• engineer and operations chap
• open source chap
• funny accent

The Docker Book

www.dockerbook.com

Who are you folks?

What's this going to be all about?

• What
• Why
• How

So what is Docker?

• Container virtualization
• Build, pack, ship and run applications as containers
• Build once, run in many places
• Isolated and content agnostic

But this isn't new?!!?

So why should I care?

• Easy (and lightweight!) way to model reality
• Devs care about their app, Ops cares about the containers
• Golden images without the overhead

Why developers care...

• A clean, safe, hygienic and portable runtime environment
• No worries about missing dependencies, packages and other pain points
• Run each app in its own isolated container, so you can run various versions of libraries and other dependencies
• Automate testing, integration, packaging
• Reduce/eliminate concerns about compatibility on different platforms

Why operations care...

• Make the entire lifecycle more efficient, consistent, and repeatable
• Increase the quality of code produced by developers
• Eliminate inconsistencies between development, test, and production environments
• Support segregation of duties
• Significantly improves the speed and reliability of continuous deployment and integration

So why not VMs or Cloud?

• Speed of deployment
• Portability
• Size aka cached layering FTW
• Density & Performance
• Cost

Technology Stack

• Runs (for now) on most Linux distros
• cgroups and namespacing
• Device Mapper or AUFS or vfs or <pluggable in future>
• lxc or <pluggable in future>

Technology Stack

Docker Basics

• Image
• Registry
• Container

Building Docker images with a Dockerfile

           FROM       ubuntu
           MAINTAINER James Turnbull "james@example.com"
           
           RUN apt-get install -y apache2
           
           ENV APACHE_RUN_USER www-data
           ENV APACHE_RUN_GROUP www-data
           ENV APACHE_LOG_DIR /var/log/apache2
           
           EXPOSE 80
           
           ENTRYPOINT ["/usr/sbin/apache2"]
           CMD ["-D", "FOREGROUND"]
         

Building the image

$ sudo docker build -t="jamtur01/apache2" .

Pushing the image

$ sudo docker push jamtur01/apache2

Running the container

$ sudo docker run -d -p 80 -v /var/www/myapp jamtur01/apache2

Questions?