Custom Docker Image for Open Source

Have you tried open source edition of
You can get your own private CI server through the use of the open source edition. It’s really awesome.

Drone provides a lot of docker images

# these two are base images. all Drone images are built on top of these
# these are BIG (~3GB) so make sure you have a FAST internet connection
docker pull bradrydzewski/ubuntu
docker pull bradrydzewski/base

# clojure images
docker pull bradrydzewski/lein             # image: lein

** snip **

# ruby images
docker pull bradrydzewski/ruby:2.0.0       # image: ruby2.0.0
docker pull bradrydzewski/ruby:1.9.3       # image: ruby1.9.3

# scala images
docker pull bradrydzewski/scala:2.10.3     # image: scala2.10.3
docker pull bradrydzewski/scala:2.9.3      # image: scala2.9.3

However, there are many variations of image, drone supports a custom image.
For example, you can create the custom images what have any distribution, any language, any version, any databases, and any libraries you want to link. It also saves the test time, because drone doesn’t cache the test environment (except cache section on .drone.yml), build all from the scratch each test phase.

This article describe how to create a docker image for drone.

Setup Development Environment

Drone uses docker for building a sandbox for each test. While you are in Linux, install from the packager. If not use Boot2Docker. On this section, uses drone development environment on Vagrant.

Before you enter the setup process, install VirtualBox and Vagrant.

$ git clone
$ cd drone
$ vagrant up default
$ vagrant ssh default

Take a coffee break to wait for building.

$ vagrant ssh default
vagrant@precise64: $ make run

Go http://localhost:8080/install If you see the installation page, drone works fine.

Building custom image from Dockerfile

Put a Dockerfile which is instructions to build an image like this.
This is an exmaple of ruby on CentOS 6

FROM centos:centos6
MAINTAINER Kazuki Hamasaki <>

USER root

# packages
RUN yum groupinstall -y "Development Tools"
RUN yum -y install openssl openssl-devel readline-devel readline libxml2-devel libxslt-devel libyaml-devel zlib zlib-devel git --enablerepo=centosplus

# rbenv
RUN git clone /usr/local/rbenv
RUN git clone /usr/local/rbenv/plugins/ruby-build
ADD /etc/drone.d/

# ruby install
RUN bash -lc 'rbenv install 2.1.2'

# bundler
RUN bash -lc 'rbenv global 2.1.2; gem install rbenv-rehash'
RUN bash -lc 'rbenv global 2.1.2; gem install bundler'
RUN bash -lc 'rbenv rehash'

Be aware of the difference of the image conditions between official and unofficial image.

the default user for all official Drone image is the “ubuntu” user, since all build images inherit from the ubuntu cloud ISO

All other images are assumed to use the root user.

You can use the bradrydzewski/base for your base image, but it doesn’t work by this handling of unofficial images.

If you want to run the script before a test, put the script to /etc/drone.d
The drone will kick this. Drone’s shell doesn’t load /etc/profile, .bash_profile, and .bashrc.

Building image

I recommend setting the repository name with ‘-t’ option for easy reference.

$ sudo docker build --rm -t ashphy/centos6-ruby:2.1.2 .
Sending build context to Docker daemon 75.26 kB
Sending build context to Docker daemon
Step 0 : FROM ashphy/centos6-ruby:base
 ---> d793989a9b8a
Step 1 : MAINTAINER Kazuki Hamasaki <>
 ---> Using cache
 ---> 30578dc14bd9
** snip **
Step 8 : RUN bash -lc 'rbenv rehash'
 ---> Using cache
 ---> 491d71171a33
Successfully built 491d71171a33
build success

Got a special image for you.

Testing your image on the drone

Now let’s check your image if it works well on the drone.

Prepare the test repository, you want to test. Set the image name you build at the image section on .drone.yml file like below.

image: ashphy/centos6-ruby:2.1.2
  - bundle install
  - rspec

Test on the drone with following command.

$ /opt/go/src/ build .

Uploading your image to the docker hub

If the image specified by .drone.yml is missing, drone will do ‘docker pull’, This means that the image will be downloaded from docker hub.
So that your private image that cannot be upload to public is needed to build on the drone server.

Please register in advance at

$ sudo docker publish ashphy/centos6-ruby

CentOS6 + ruby image

I created custom images with CentOS6 + rbenv + ruby.
Put images to centos6-ruby. And Dockerfiles to

I hope you find it informative.