Docker 101: An Introduction
1 like1,031 views
This document provides an introduction to Docker presented by Tibor Vass, a core maintainer on Docker Engine. It outlines challenges with traditional application deployment and argues that Docker addresses these by providing lightweight containers that package code and dependencies. The key Docker concepts of images, containers, builds and Compose are introduced. Images are read-only templates for containers which sandbox applications. Builds describe how to assemble images with Dockerfiles. Compose allows defining multi-container applications. The document concludes by describing how Docker improves the deployment workflow by allowing testing and deployment of the same images across environments.
![Build images
• Example layout of a Dockerfile placed alongside with the code
• FROM ubuntu:14.04
• RUN apt-get update && apt-get install -y golang
• ENV GOPATH=/go
• COPY . /go/src/myapp
• EXPOSE 8080
• RUN go build myapp
• CMD [“/go/bin/myapp”]
• Build new image named myapp: docker build -t myapp .
• Change code, and rerun the build command: notice that Docker cached the dependencies and
won’t fetch them again by default (use —no-cache if desired)
47](https://image.slidesharecdn.com/docker-posscon-150427120125-conversion-gate01/85/Docker-101-An-Introduction-47-320.jpg)
Docker 101: An Introduction
- 1. Another introduction to Docker Tibor Vass
- 2. Who Am I? • Core maintainer on Docker Engine • Previously Ops @ StumbleUpon • I ♡ Go 2 Tibor Vass, Chapel Hill, NC IRC #docker: tibor Twitter: @tiborvass
- 3. Outline • Challenges • What’s needed • What is Docker • Getting started • Docker concepts – Engine – Images & Containers – Builds – Compose • Deployment Workflow 3
- 4. Challenges
- 5. 1. Deployment & Guarantees
- 6. 1. Separation of concerns (Dev vs Ops)
- 7. Code deployment… 7 CI fetches code builds it and runs tests If ok, allow deployment of code push code to git server Prod Deploy code hook kicks CI
- 8. … in different environments! 8 Newest version of Python Code assumes port 1234 available Older version of Python Port 1234 taken Missing dependency
- 9. … in different environments! 9 Newest version of Python Code assumes port 1234 available Older version of Python Port 1234 taken Missing dependency Angry Users
- 10. … in different environments! 10 Newest version of Python Code assumes port 1234 available Older version of Python Port 1234 taken Missing dependency Angry Users “Works for me!”
- 13. 13 Code deployment Need “Code + environment” deployment
- 14. 14 Code deployment Need “Code + environment” deployment Need a portable unit of deployment (guaranteed to work everywhere)
- 16. 2. Density & Resource usage
- 17. Density & Resource usage • One app per server – waste of idle resources – huge costs • One app per VM, multiple VMs per server – Better resource pooling – Easier to scale – Pay as you go (cloud) – Not *that* portable – Requires resource allocation (cpu, RAM, disk, …) – GuestOS duplicated – Resource hungry 17 Hardware Host OS Hypervisor GuestOS GuestOS AppApp Hardware Host OS App
- 18. 3. Move fast, and don’t break things
- 19. 19 Make your product better faster (stronger♫) to gain competitive advantage
- 20. What’s needed
- 21. What’s needed • Something like VMs… • Isolates processes from storage, networking, memory, cpu (sandboxing) • …but lighter • Lightweight portable unit of deployment (packaging & distribution) 21
- 23. 23 Hardware Host OS App App App
- 24. 24 Hardware Host OS Hardware Host OS Hypervisor GuestOS GuestOS code bins/libs code bins/libs code code code bins/libsshared bins/libs As many shared layers as possible VM Container VM vs Container
- 25. What is Docker?
- 26. Challenge #0: Satisfying Users’ expectation of reliability and availability
- 27. 27 Dream: what if, you could build distributed apps easily, and focus on your product?
- 28. 28 Distributed and scalable services gotta be independent from the machines they run on
- 29. 29 Containers are part of the answer
- 30. 30 Docker’s greatest value does not lie in its technology
- 31. 31 It lies in its ability to get people agree on something
- 32. 32 Open platform inviting you to help make the dream happen
- 33. 33 Or simply enjoy and contribute to each independent piece along the way
- 34. Docker • Engine • Hub • Distribution (Private registry) • Machine • Compose • Swarm • Kitematic • More to come… 34
- 35. Getting Started
- 37. 37 (install Machine and Compose as well)
- 38. Docker concepts
- 39. 1. Engine
- 40. Engine • Docker Daemon + REST(ish) API • Docker Client (CLI) talks to the API • Daemon manages the Docker containers • Start it with: docker -d • docker version to test if docker is set up correctly 40
- 41. 2. Images & Containers
- 42. Images vs Containers • Images: About storing or moving your app • Containers: About running your app 42
- 43. Image • Read-only snapshots (templates) for creating containers • Stored on the Docker Hub or on a private registry (or in a tar archive) • Cannot be run, has to be instantiated into a container • Look around on Docker Hub for existing images • List images: docker images • Download busybox: docker pull busybox • Remove busybox image: docker rmi busybox 43
- 44. Containers • Sandboxed application • docker ps • docker create —name hello busybox echo hello posscon • docker start -a hello • docker start -a hello # same container started again • docker rm hello • docker run busybox echo hello posscon • WARNING: run = create + start, so each “run” spawns a new container (ephemeral) 44
- 45. Containers • Launch an interactive shell: docker run -i -t busybox sh • Expose ports of an image: docker run -P training/webapp python app.py • Read host port on docker ps • Detached mode: docker run -d -P training/webapp python app.py • Expose to specific host ports: docker run -d -p 1234:5000 training/webapp python app.py 45
- 46. 3. Builds aka Dockerizing
- 47. Build images • Example layout of a Dockerfile placed alongside with the code • FROM ubuntu:14.04 • RUN apt-get update && apt-get install -y golang • ENV GOPATH=/go • COPY . /go/src/myapp • EXPOSE 8080 • RUN go build myapp • CMD [“/go/bin/myapp”] • Build new image named myapp: docker build -t myapp . • Change code, and rerun the build command: notice that Docker cached the dependencies and won’t fetch them again by default (use —no-cache if desired) 47
- 48. Build with official images • No need to use FROM ubuntu and install common dependencies anymore! • Use official golang image: • FROM golang • COPY . /go/src/myapp • … • Even simpler: • FROM golang:onbuild • # something will listen on port 8080 • EXPOSE 8080 48
- 49. 4. Compose
- 50. Compose your stack of containers • In a docker-compose.yml: • wordpress: • image: wordpress • links: • - db:mysql • ports: • - 8080:80 • db: • image: mariadb • environment: • MYSQL_ROOT_PASSWORD: example • docker-compose up • http://<IP>:8080 where IP is the IP of the Docker daemon 50
- 52. App deployment… 52 CI fetches code builds an IMAGE on which it runs tests push code to git server hook kicks CI Prod Docker Hub or private registry If ok, push IMAGE to registry Deploy IMAGE
- 53. … in different environments! 53 Dockerfile described the Docker image with its dependencies and Dev tested his code in that Docker image Same Dockerfile Same Docker image Docker image safely stored and tagged
- 54. Learn more
- 55. Learn more • https://docs.docker.com/ • swarm • security • machine • volumes • exec • logging • monitoring 55
- 56. THANK YOU