Dockerizing simple Sinatra app using docker and fig

Posted on  12/8/2014

Docker is new hotness in market , docker use kernel level namespace’s and cgroups to create isolated container environment . according to Wikipedia .

UPDATE : fig is now merged in docker and now its called : compose  


Docker is an open-source project that automates the deployment of applications inside software containers, by providing an additional layer of abstraction and automation of operating system–level virtualization on Linux.[Docker uses resource isolation features of the Linux kernel such as cgroups and kernel namespaces to allow independent “containers” to run within a single Linux instance, avoiding the overhead of starting virtual machines.

docker logo
docker logo

If you know what is lxc and thinking what is difference between LXC and docker then give a look at this excellent post : .

Install Docker

lets first install docker , You can use official Documentation to get up running docker

$ sudo apt-get install curl
$ curl -sSL | sudo sh

and lets install fig

$ sudo apt-get install python-pip
$ sudo pip install fig

Lets test our installation

$ docker --version && fig --versions

# lets run simple hello world inside a ubuntu container
$ sudo docker run -i -t ubuntu /bin/echo "Hello from container "

Sample output

[email protected]:~$ sudo docker run -i -t ubuntu /bin/echo "Hello from container "
Hello from container

give non root access for avoiding using sudo every time with docker command .

$ sudo groupadd docker
$ sudo gpasswd -a ${USER} docker
$ sudo service docker restart

okay so , I wrote this simplest sinatra app , its contains five files 2 of them related to gem file and app.rb is our app and fig.yml will be used as fig configuration file and Dockerfile will be used to build our image

[email protected]:~/code/ruby/app$ tree

├── app.rb
├── Dockerfile
├── fig.yml
├── Gemfile
└── Gemfile.lock

# app.rb

require "sinatra "

get '/'
"Hello World !"

and created Gemfille

source ''

gem 'sinatra'

okay , now lets build ruby image , I build using dockerfile because its take too much to download 800MB file .
okay . you can clone all this from github .


FROM ubuntu
RUN apt-get update

RUN apt-get -y update
RUN apt-get -y install git git-core curl gawk g++ gcc make libc6-dev libreadline6-dev \
zlib1g-dev libssl-dev libyaml-dev libsqlite3-dev sqlite3 autoconf \
libgdbm-dev libncurses5-dev automake libtool bison pkg-config libffi-dev

RUN apt-get install -y postgresql postgresql-contrib postgresql-client libpq5 libpq-dev
RUN curl -sSL | gpg --import -

RUN curl -L | bash -s stable

ENV PATH /usr/local/rvm/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin

RUN rvm install ruby-2.1.5
RUN rvm reload
CMD source /etc/profile
CMD source /usr/local/rvm/scripts/rvm
RUN apt-get install -y nodejs npm
RUN ln -s /usr/bin/nodejs /usr/bin/node
RUN ["/bin/bash", "-l", "-c", "rvm use 2.1.5 --default" ]
RUN ["/bin/bash", "-l", "-c", "rvm requirements; gem install bundler --no-ri --no-rdoc"]
RUN ["/bin/bash", "-l", "-c", "gem list"]
RUN apt-get update -qq && apt-get install -y build-essential libpq-dev
RUN mkdir /myapp
WORKDIR /myapp
ADD Gemfile /myapp/Gemfile
RUN ["/bin/bash", "-l", "-c", "bundle install "]

fig is small utility that’s provide functionality to set up quick development environment . all it require a file fig.yml . read more about fig on fig’s website :

# fig.yml
build: .
command: ["/bin/bash", "-l", "-c", "ruby app.rb"]
- .:/myapp
- "8000:4567"

just use this Dockerfile to build image . you can tag use tag this image to use this image for your next ruby project .

$ git clone
$ cd sinatra_container
$ docker build -t="ubuntu/sinatra" .
$ fig build
$ fig up

it will take some time to build , it will install ruby using rvm and sinatra app .

fig up sample output

sinatra docker
sinatra docker

now open your browser and point it to : http://localhost:8000 .
you will hello world program .

sinatra docker
sinatra docker

Thats all for now , thanks for reading .

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