CMD and ENTRYPOINT better together
In case you don't know ENTRYPOINT makes your dockerized application behave like a binary. You can pass arguments to the ENTRYPOINT during
docker run and not worry about it being overwritten ( unlike CMD ). ENTRYPOINT is even better when used with CMD. Let's checkout my Rethinkdb Dockerfile and see how to use this.# Dockerfile for Rethinkdb
# http://www.rethinkdb.com/
FROM ubuntu
MAINTAINER Michael Crosby <michael@crosbymichael.com>
RUN echo "deb http://archive.ubuntu.com/ubuntu precise main universe" > /etc/apt/sources.list
RUN apt-get update
RUN apt-get upgrade -y
RUN apt-get install -y python-software-properties
RUN add-apt-repository ppa:rethinkdb/ppa
RUN apt-get update
RUN apt-get install -y rethinkdb
# Rethinkdb process
EXPOSE 28015
# Rethinkdb admin console
EXPOSE 8080
# Create the /rethinkdb_data dir structure
RUN /usr/bin/rethinkdb create
ENTRYPOINT ["/usr/bin/rethinkdb"]
CMD ["--help"]
This is everything that is required to get Rethinkdb dockerized. We have my standard 5 lines at the top to make sure the base image is updated, ports exposed, etc... With the ENTRYPOINT set, we know that whenever this image is run, all arguments passed during
docker run will be arguments to the ENTRYPOINT ( /usr/bin/rethinkdb ).
References:
- http://crosbymichael.com/dockerfile-best-practices.html
