Development Quickstart

This page describes how to setup and use a working Python development environment that can be used in developing nova on Ubuntu, Fedora or Mac OS X. These instructions assume you’re already familiar with git.

Following these instructions will allow you to build the documentation and run the nova unit tests. If you want to be able to run nova (i.e., launch VM instances), you will also need to — either manually or by letting DevStack do it for you — install libvirt and at least one of the supported hypervisors. Running nova is currently only supported on Linux, although you can run the unit tests on Mac OS X.


For how to contribute to Nova, see HowToContribute. Nova uses the Gerrit code review system, GerritWorkflow.


There are two ways to create a development environment: using DevStack, or explicitly installing and cloning just what you need.

Using DevStack

See Devstack Documentation. If you would like to use Vagrant, there is a Vagrant for DevStack.

Explicit Install/Clone

DevStack installs a complete OpenStack environment. Alternatively, you can explicitly install and clone just what you need for Nova development.

Getting the code

Grab the code from git:

git clone
cd nova

Linux Systems

The first step of this process is to install the system (not Python) packages that are required. Following are instructions on how to do this on Linux and on the Mac.


This section is tested for Nova on Ubuntu (14.04-64) and Fedora-based (RHEL 6.1) distributions. Feel free to add notes and change according to your experiences or operating system.

Install the prerequisite packages listed in the bindep.txt file.

On Debian-based distributions (e.g., Debian/Mint/Ubuntu):

sudo apt-get install python-pip
sudo pip install tox
tox -e bindep
sudo apt-get install <indicated missing package names>

On Fedora-based distributions (e.g., Fedora/RHEL/CentOS/Scientific Linux):

sudo yum install python-pip
sudo pip install tox
tox -e bindep
sudo yum install <indicated missing package names>

On openSUSE-based distributions (SLES, openSUSE Leap / Tumbleweed):

sudo zypper in python-pip
sudo pip install tox
tox -e bindep
sudo zypper in <indicated missing package names>

Mac OS X Systems

Install virtualenv:

sudo easy_install virtualenv

Check the version of OpenSSL you have installed:

openssl version

The stock version of OpenSSL that ships with Mac OS X 10.6 (OpenSSL 0.9.8l) or Mac OS X 10.7 (OpenSSL 0.9.8r) or Mac OS X 10.10.3 (OpenSSL 0.9.8zc) works fine with nova. OpenSSL versions from brew like OpenSSL 1.0.1k work fine as well.

Brew is very useful for installing dependencies. As a minimum for running tests, install the following:

brew install python3 postgres
python3 -mpip install tox

Building the Documentation

Install the prerequisite packages: graphviz

To do a full documentation build, issue the following command while the nova directory is current.

tox -edocs

That will create a Python virtual environment, install the needed Python prerequisites in that environment, and build all the documentation in that environment.

Running unit tests

See Running Python Unit Tests.

Note that some unit and functional tests use a database. See the file tools/ on how the databases are set up in the OpenStack CI environment and replicate it in your test environment.

Using the pre-commit hook

Nova can make use of the pre-commit framework to allow running of some linters on each commit. This must be enabled locally to function:

$ pip install --user pre-commit
$ pre-commit install --allow-missing-config

As a reminder, the hooks are optional and you are not enforced to run them. You can either not install pre-commit or skip the hooks once by using the --no-verify flag on git commit.

Using a remote debugger

Some modern IDE such as pycharm (commercial) or Eclipse (open source) support remote debugging. In order to run nova with remote debugging, start the nova process with the following parameters:

--remote_debug-host <host IP where the debugger is running>
--remote_debug-port <port it is listening on>

Before you start your nova process, start the remote debugger using the instructions for that debugger:

More detailed instructions are located here -

Using fake computes for tests

The number of instances supported by fake computes is not limited by physical constraints. It allows you to perform stress tests on a deployment with few resources (typically a laptop). Take care to avoid using scheduler filters that will limit the number of instances per compute, such as NumInstancesFilter.

Fake computes can also be used in multi hypervisor-type deployments in order to take advantage of fake and “real” computes during tests:

  • create many fake instances for stress tests

  • create some “real” instances for functional tests

Fake computes can be used for testing Nova itself but also applications on top of it.