Dockerfile Basics Workshop #2
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This document discusses the basics of Dockerfiles, which are used to automate the creation of Docker images. It covers common Dockerfile instructions like FROM, RUN, EXPOSE, ENTRYPOINT and USER. It provides examples of Dockerfiles for Memcached and WordCount images. It also describes using docker build to create images from Dockerfiles and testing the images. Finally, it recommends an online tutorial for learning more about writing Dockerfiles.
![ENTRYPOINT 2/2
• Run containers as executables! :)
• Dockerfile: https://github.com/jbarbier/Dockerfile-Basics-Docker-Workshop-2-
Twitter/blob/master/slide_10/Dockerfile
# This is wc
#
# VERSION 0.42
# use the base image provided by Docker
FROM base
MAINTAINER Roberto roberto@docker.com
# count lines with wc
ENTRYPOINT ["wc", "-l"]
42h
$ cat /etc/passwd | docker run -i wc](https://image.slidesharecdn.com/dockerfilebasics-workshop-twitter-2013-11-05-131105154723-phpapp01-140801194854-phpapp01/85/Dockerfile-Basics-Workshop-2-10-320.jpg)
Dockerfile Basics Workshop #2
- 1. Dockerfile Basics Docker workshop #2 at @Twitter, beginners class #dockerworkshop By Julien Barbier @julienbarbier42 @ Docker version 0.6.5
- 2. Dockerfiles • Dockerfiles = image representations • Simple syntax for building images • Automate and script the images creation 42h
- 3. FROM • Sets the base image for subsequent instructions • Usage: FROM <image> • Example: FROM ubuntu • Needs to be the first instruction of every Dockerfile • TIP: find images with the command: docker search 42h
- 4. RUN • Executes any commands on the current image and commit the results • Usage: RUN <command> • Example: RUN apt-get install –y memcached FROM ubuntu RUN apt-get install -y memcached is equivalent to: $ docker run ubuntu apt-get install -y memcached $ docker commit XXX 42h
- 5. docker build Creates an image from a Dockerfile • From the current directory • From stdin • From GitHub TIP: Use –t to tag your image $ docker build github.com/creack/docker-firefox $ docker build - < Dockerfile $ docker build . 42h
- 6. Example: Memcached FROM ubuntu RUN echo "deb http://archive.ubuntu.com/ubuntu precise main universe" > /etc/apt/sources.list RUN apt-get update RUN apt-get install -y memcached • Dockerfile: https://github.com/jbarbier/Dockerfile-Basics-Docker-Workshop-2- Twitter/blob/master/slide_6/Dockerfile • Test it $ docker run -i -t memcached_d1 /bin/bash root@1f452c9442fb:/# memcached -u daemon -vvv $ docker build –t memcached_d1 . 42h
- 7. #Commenting • # • Dockerfile: https://github.com/jbarbier/Dockerfile-Basics-Docker-Workshop-2- Twitter/blob/master/slide_7/Dockerfile # Memcached # # VERSION 1.0 # use the ubuntu base image provided by Docker FROM ubuntu # make sure the package repository is up to date RUN echo "deb http://archive.ubuntu.com/ubuntu precise main universe" > /etc/apt/sources.list RUN apt-get update # install memcached RUN apt-get install -y memcached 42h
- 8. MAINTAINER • specify name / contact of the person maintaining the Dockerfile • Example: MAINTAINER Julien, [email protected] • Dockerfile: https://github.com/jbarbier/Dockerfile-Basics-Docker-Workshop-2- Twitter/blob/master/slide_8/Dockerfile # Memcached # # VERSION 1.0 # use the ubuntu base image provided by Docker FROM ubuntu MAINTAINER Julien, [email protected] # make sure the package repository is up to date RUN echo "deb http://archive.ubuntu.com/ubuntu precise main universe" > /etc/apt/sources.list RUN apt-get update # install memcached RUN apt-get install -y memcached 42h
- 9. ENTRYPOINT 1/2 • Triggers a command as soon as the container starts • Example: ENTRYPOINT echo “Whale You Be My Container?” • Dockerfile: https://github.com/jbarbier/Dockerfile-Basics-Docker-Workshop-2-Twitter/blob/master/slide_9/Dockerfile # Whale you be my container? # # VERSION 0.42 # use the base image provided by Docker FROM base MAINTAINER Moby Dock [email protected] # say hello when the container is launched ENTRYPOINT echo "Whale you be my container" 42h
- 10. ENTRYPOINT 2/2 • Run containers as executables! :) • Dockerfile: https://github.com/jbarbier/Dockerfile-Basics-Docker-Workshop-2- Twitter/blob/master/slide_10/Dockerfile # This is wc # # VERSION 0.42 # use the base image provided by Docker FROM base MAINTAINER Roberto [email protected] # count lines with wc ENTRYPOINT ["wc", "-l"] 42h $ cat /etc/passwd | docker run -i wc
- 11. USER • Sets the username to use when running the image • Example: USER daemon 42h
- 12. EXPOSE • Sets ports to be exposed to other containers when running the image (cf lightning talk by Michael Crosby @crosbymichael) • Example: EXPOSE 80 42h
- 13. Exercice: create a perfect Memcached Dockerfile Answer https://github.com/jbarbier/Dockerfile-Basics-Docker-Workshop-2-Twitter/blob/master/memcached/Dockerfile #BOOM • Try it (update port number, $ docker ps) Python https://github.com/jbarbier/Dockerfile-Basics-Docker-Workshop-2-Twitter/blob/master/memcached/test.py Ruby https://github.com/jbarbier/Dockerfile-Basics-Docker-Workshop-2-Twitter/blob/master/memcached/test.rb PHP https://github.com/jbarbier/Dockerfile-Basics-Docker-Workshop-2-Twitter/blob/master/memcached/test.php 42h $ docker build -t memcached . $ docker run –p 11211 memcached
- 14. Quizz: Online Dockerfile Tutorials Test your skills here: http://www.docker.io/learn/dockerfi le/ 42h