:title: Setting Up a Dev Environment
:description: Guides on how to contribute to docker
:keywords: Docker, documentation, developers, contributing, dev environment

Setting Up a Dev Environment
^^^^^^^^^^^^^^^^^^^^^^^^^^^^

To make it easier to contribute to Docker, we provide a standard
development environment. It is important that the same environment be
used for all tests, builds and releases. The standard development
environment defines all build dependencies: system libraries and
binaries, go environment, go dependencies, etc.


Step 1: Install Docker
----------------------

Docker's build environment itself is a Docker container, so the first
step is to install Docker on your system.

You can follow the `install instructions most relevant to your system
<https://docs.docker.io/en/latest/installation/>`_.  Make sure you have
a working, up-to-date docker installation, then continue to the next
step.


Step 2: Install tools used for this tutorial
--------------------------------------------

Install ``git``; honest, it's very good. You can use other ways to get the Docker
source, but they're not anywhere near as easy.

Install ``make``. This tutorial uses our base Makefile to kick off the docker
containers in a repeatable and consistent way. Again, you can do it in other ways
but you need to do more work.

Step 3: Check out the Source
----------------------------

.. code-block:: bash

    git clone http://git@github.com/dotcloud/docker
    cd docker

To checkout a different revision just use ``git checkout`` with the name of branch or revision number.


Step 4: Build the Environment
-----------------------------

This following command will build a development environment using the Dockerfile in the current directory. Essentially, it will install all the build and runtime dependencies necessary to build and test Docker. This command will take some time to complete when you first execute it.

.. code-block:: bash

    sudo make build

If the build is successful, congratulations! You have produced a clean build of 
docker, neatly encapsulated in a standard build environment. 


Step 5: Build the Docker Binary
-------------------------------

To create the Docker binary, run this command:

.. code-block:: bash

	sudo make binary

This will create the Docker binary in ``./bundles/<version>-dev/binary/``

Using your built Docker binary
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The binary is available outside the container in the directory 
``./bundles/<version>-dev/binary/``. You can swap your host docker executable 
with this binary for live testing - for example, on ubuntu: 

.. code-block:: bash

	sudo service docker stop ; sudo cp $(which docker) $(which docker)_ ; sudo cp ./bundles/<version>-dev/binary/docker-<version>-dev $(which docker);sudo service docker start
	
.. note:: Its safer to run the tests below before swapping your hosts docker binary.


Step 5: Run the Tests
---------------------

To execute the test cases, run this command:

.. code-block:: bash

	sudo make test

If the test are successful then the tail of the output should look something like this

.. code-block:: bash

	--- PASS: TestWriteBroadcaster (0.00 seconds)
	=== RUN TestRaceWriteBroadcaster
	--- PASS: TestRaceWriteBroadcaster (0.00 seconds)
	=== RUN TestTruncIndex
	--- PASS: TestTruncIndex (0.00 seconds)
	=== RUN TestCompareKernelVersion
	--- PASS: TestCompareKernelVersion (0.00 seconds)
	=== RUN TestHumanSize
	--- PASS: TestHumanSize (0.00 seconds)
	=== RUN TestParseHost
	--- PASS: TestParseHost (0.00 seconds)
	=== RUN TestParseRepositoryTag
	--- PASS: TestParseRepositoryTag (0.00 seconds)
	=== RUN TestGetResolvConf
	--- PASS: TestGetResolvConf (0.00 seconds)
	=== RUN TestCheckLocalDns
	--- PASS: TestCheckLocalDns (0.00 seconds)
	=== RUN TestParseRelease
	--- PASS: TestParseRelease (0.00 seconds)
	=== RUN TestDependencyGraphCircular
	--- PASS: TestDependencyGraphCircular (0.00 seconds)
	=== RUN TestDependencyGraph
	--- PASS: TestDependencyGraph (0.00 seconds)
	PASS
	ok  	github.com/dotcloud/docker/utils	0.017s

If $TESTFLAGS is set in the environment, it is passed as extra arguments to 'go test'.
You can use this to select certain tests to run, eg.

    TESTFLAGS='-run ^TestBuild$' make test


Step 6: Use Docker
-------------------

You can run an interactive session in the newly built container: 

.. code-block:: bash

	sudo make shell

	# type 'exit' or Ctrl-D to exit


Extra Step: Build and view the Documentation
--------------------------------------------

If you want to read the documentation from a local website, or are making changes
to it, you can build the documentation and then serve it by:

.. code-block:: bash

	sudo make docs
    # when its done, you can point your browser to http://yourdockerhost:8000
	# type Ctrl-C to exit


**Need More Help?**

If you need more help then hop on to the `#docker-dev IRC channel <irc://chat.freenode.net#docker-dev>`_ or post a message on the `Docker developer mailing list <https://groups.google.com/d/forum/docker-dev>`_.
