Docker introduction
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This document provides an introduction and overview of Docker. It discusses what Docker is and how it differs from virtual machines by using layers, containers, and shared resources. Docker aims to solve the problem of inconsistent environments between development, testing, and production by allowing applications and their dependencies to be packaged into standardized units called containers that can run on any Docker host. The document provides instructions on installing Docker and using basic commands like running, publishing ports, and mounting volumes for containers. It also covers some tips, tricks, pitfalls, and references for further reading.
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Docker introduction
- 1. Docker Introduction By Walter Liu 2014/08/25
- 2. Agenda • What is Docker? • How to use Docker? • Miscellaneous – Pitfall during POC – Tips and tricks – Some references
- 5. Difference with VM Virtual Machines Docker
- 6. Difference with VM – Memory is acquired when needed. – Disk is acquired when needed. • (If use devicemapper has had 10 GB limitation) – Some file system is readonly. • Need to use priority mode to change it, but be careful about that. I destroyed the container during functional test.
- 7. File System Copy on write
- 8. What does Docker want to solve? The Matrix From Hell
- 9. Many Payloads …... • RHEL 4 • CentOS 5 • CentOS 6 • CentOS 7 • ……
- 10. Many Payloads …... • C/C++ • C/C++ libraries • Python2.3/2.4/2.6 • Python Libs • Boostpython • Ruby • Php • Java • …..
- 11. Many Payloads …... • Nginx • Apache • Uwsgi • Django • Bottle • …..
- 12. Many Payloads …... + our application
- 13. Many targets • Your dev environment • Co-worker dev environment • QA test environment • Staging environment • Production environment • Customized environment
- 14. How do we want to use it? • Same environment between RD and OPS. • Faster delivery • Run old Linux in new Linux environment. – OPS could upgrade system OS without worry if old application’s env. – If 2 applications are bound together, by using Docker their OS env could be upgraded at different time. • Upgrade host OS without changing application.
- 15. How others use it? • Easy Application Deployment • Continuous Integration • Continuous Delivery • Platform-as-a-Service (PaaS) • Development Environments & Build Pipelines - Spotify
- 17. Continuous Integration/Delivery • Write code • Push to git • Jenkins is triggered to build container and test the container. • If the test is successful, push to private docker registry. (Continuous Integration) • Automatic pull newest docker image to staging/production server and switch load balance from previous version. (Continuous Delivery)
- 18. Development Environments & Build Pipelines
- 19. Docker Requirement/Dependency • Linux Kernel 3.8+ – CentOS 6.5+ (CentOS 7 is recommended) – Ubuntu is officially recommended. • AUFS Support – (Not in CentOS, need Kernel patch) • Cgroups and namespaces (Kernel 2.6.38+) • lxc • xz-utils
- 20. HOW TO USE DOCKER?
- 22. Installation • yum install docker-io #EPEL repo • service docker start • chkconfig docker on • Option: – Add a user to run docker as root.
- 23. Import Image • From docker repository – CMD: docker pull centos • From a tar ball – CMD: docker load centos-wcs-build-1000.tar • From private docker repository
- 24. Run container • docker run –it <image_id> /bin/bash • Run docker container as a service – Use supervisor is a good choice. – Check example https://github.com/Krijger/docker-cookbooks – And http://docs.docker.com/articles/using_supervisord/ • Note: if the process terminated, the container is terminated too.
- 25. Mount volume in a container • option: -v , could be used multiple times to mount multiple volume. • syntax: – docker run -v <host_path>:<container_path> ….. – docker run -v <host_path>:<container_path>:rw ….. – docker run -v <host_path>:<container_path>:ro ….. • Example: docker run –it –v /trend/wcs/ptn:/trend/wcs/ptn:ro <image_id> /bin/bash
- 26. Publish port • Option: “-p" Could be used multiple times to publish multiple ports to host. • syntax: – docker run –P …. # Publish all ports to host, it’s big P. – docker run –p <host_container_port> …. # random port – docker run –p <host_port>:<container_port> …. – docker run – p <host_interface_ip>:<host_port>:<container_port> …. • Example: docker run –P <image_id> "/trend/wcs/wcsd" "/trend/wcs/conf/wcs.config"
- 27. Dockerfile example This is not correct.
- 28. MISCELLANEOUS
- 29. Pitfall during POC • Use too old Linux kernel (CentOS 6.4) • Use priority mode – Crash the container, all commands printed core dump. • Run IO-heavy job on devicemapper. (4x slow) • Host and container uid is not sync. – WORKAROUND: adduser –u 1000 –g 1000 wcs
- 30. Tips and tricks • Kill all containers – docker kill $(docker ps -q) • Remove contents of all containers – docker rm $(docker ps -a –q) • Remove all images – docker rmi $(docker images -q -a) • Inspect IP of the container that just ran, – CID=$(docker run -d -p 4321 base nc -lk 4321) – docker inspect --format '{{ .NetworkSettings.IPAddress }}' ${CID}
- 31. Some References • 使用DEVICE MAPPER 插件来改变DOCKER 容 器的大小 https://www.dockboard.org/resizing-docker-containers- with-the-device-mapper-plugin/ • WHY YOU DON'T NEED TO RUN SSHD IN YOUR DOCKER CONTAINERS? – http://blog.docker.com/2014/06/why-you-dont-need- to-run-sshd-in-docker/
- 33. Backup slides
- 34. The problems • OPS needs to do – Installation, – Dependency – Monitor • Environment conflict • Environment diff between Dev and production
Editor's Notes
- #10: Idea from a slide in slideshare.