The document describes how to build Docker images from Dockerfiles. It explains the main Dockerfile instructions including FROM, MAINTAINER, ADD, ENV, RUN, CMD, ENTRYPOINT, EXPOSE and VOLUME. It provides examples of each instruction and concludes by showing how to build an image running MongoDB using these instructions.

1. Building Images
from Dockerfiles
Tyler Brock
@tylerbrock

2. FROM - specify base
image
FROM <image>
Or
FROM <image>:<tag>
FROM ubuntu
FROM ubuntu:latest
FROM ubuntu:precise (LTS)

3. MAINTAINER - blame
MAINTAINER <name>
MAINTAINER Tyler Brock,
tyler@mongodb.com

4. ADD - copy a file
ADD <src> <dest>
ADD myhax.rb /folder/for/hax/hax.rb

5. ENV - set the mood
ENV <key> <value>
ENV AWS-KEY ACBD123123EFECBD

6. RUN - get shit done
RUN <command>
RUN apt-get install htop

7. CMD - what should it do?
● CMD ["executable","param1","param2"] (like an exec,
preferred form)
● CMD ["param1","param2"] (as default parameters to
ENTRYPOINT)
● CMD command param1 param2 (as a shell)

8. ENTRYPOINT - start here
ENTRYPOINT ["executable", "param1", "param2"] (like an
exec, preferred form)
ENTRYPOINT command param1 param2 (as a shell)
ENTRYPOINT wc -l -
CMD ["-l", "-"]
ENTRYPOINT ["/usr/bin/wc"]

9. EXPOSE - connect here
EXPOSE <port> [<port>...]
EXPOSE 80

10. VOLUME
VOLUME ["/data"]
The VOLUME instruction will add one or more
new volumes to any container created from
the image.
Puts /data here: /var/lib/docker/volumes/

11. Dockerfile - the main
event
# What image are we using?
FROM ubuntu
# Take some credit
MAINTAINER Tyler Brock, tyler@mongodb.com
# Add 10gen official apt source to the sources list
RUN apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv 7F0CEB10
RUN echo 'deb http://downloads-distro.mongodb.org/repo/ubuntu-upstart dist 10gen' | tee /etc/apt/sources.list.d/10gen.list
# Hack for initctl not being available in Ubuntu
RUN dpkg-divert --local --rename --add /sbin/initctl
RUN ln -s /bin/true /sbin/initctl
# Install MongoDB
RUN apt-get update
RUN apt-get install mongodb-10gen
# Install a sensible config
ADD mongod.conf /etc/mongod.conf
# Setup the image as an executable that runs MongoDB
CMD ["--config", "/etc/mongod.conf"]
ENTRYPOINT ["/usr/bin/mongod"]
EXPOSE 27017

12. Build, Run, Enjoy
docker build -t <repo/image name> /path/to/dockerfiledir
docker build -t tbrock/mongodb .
docker -d -v <host>:<container> <image/tag>
docker run -d -v /home/ubuntu/data:
/data tbrock/mongodb