This document describes the development process of KIWI NG and how you can be part of it. This description applies to version 10.0.26.

The Basics

The core appliance builder is developed in Python and follows the test driven development rules.

If you want to implement a bigger feature, consider opening an issue on GitHub first to discuss the changes. Or join the discussion in the #kiwi channel on

Fork the upstream repository

  1. On GitHub, navigate to:

  2. In the top-right corner of the page, click Fork.

Create a local clone of the forked repository

$ git clone

$ git remote add upstream

Install Required Operating System Packages

KIWI NG requires additional packages at runtime which are not provided by pip. Those will be pulled in by installing the following package:

  • kiwi-systemdeps

The package is provided on the Open Build Service in the Virtualization:Appliances:Builder project. For manual inspection of the packages that are pulled in from the above kiwi-systemdeps package, please refer to the package/python-kiwi-spec-template spec file from the checked out Git repository.

Create a Python Virtual Development Environment

The following commands initializes and activates a development environment for Python 3:


KIWI NG uses tox to create a devel environment and to run tests, linters and other tasks in the tox generated environment. A tox version >= 3.3 is required for this setup process. On your host a python version >= 3.9 is required for tox to work.

$ poetry install

The command above automatically creates the application script called kiwi-ng, which allows you to run KIWI NG from the Python sources inside the virtual environment using Poetry:

$ poetry run kiwi-ng --help

Running the Unit Tests

We use tox to run the unit tests. Tox sets up its own virtualenvs inside the .tox directory for multiple Python versions and should thus not be invoked from inside your development virtualenv.

Before submitting your changes via a pull request, ensure that all tests pass and that the code has the required test coverage via the command:

$ tox

We also include pytest-xdist in the development virtualenv which allows to run the unit tests in parallel. It is turned off by default but can be enabled via:


where you can insert an arbitrary number as NUMBER_OF_PROCESSES (or a shell command like $(nproc)). Note that the double quotes around -n NUMBER_OF_PROCESSES are required (otherwise tox will consume this command line flag instead of forwarding it to pytest).

The previous call would run the unit tests for different Python versions, check the source code for errors and build the documentation.

If you want to see the available targets, use the option -l to let tox print a list of them:

$ tox -l

To only run a special target, use the -e option. The following example runs the test cases for the Python 3.11 interpreter only:

$ tox -e unit_py3_11

Create a Branch for each Feature or Bugfix

Code changes should be done in an extra Git branch. This allows for creating GitHub pull requests in a clean way. See also: Collaborating with issues and pull requests

$ git checkout -b my-topic-branch

Make and commit your changes.


You can make multiple commits which is generally useful to give your changes a clear structure and to allow us to better review your work.


Your work is important and must be signed to ensure the integrity of the repository and the code. Thus we recommend to setup a signing key as documented in Signing Git Patches.

$ git commit -S -a

Run the tests and code style checks. All of these are also performed by GitLab CI when a pull request is created.

$ tox

Once everything is done, push your local branch to your forked repository and create a pull request into the upstream repository.

$ git push origin my-topic-branch

Thank you much for contributing to KIWI NG. Your time and work effort is very much appreciated!

Coding Style

KIWI NG follows the general PEP8 guidelines with the following exceptions:

  • We do not use free functions at all. Even utility functions must be part of a class, but should be either prefixed with the @classmethod or @staticmethod decorators (whichever is more appropriate).

  • Do not set module and class level variables, put these into the classes’ __init__ method.

  • The names of constants are not written in all capital letters.


KIWI NG uses Sphinx for the API, user documentation and manual pages

tox -e doc

Document all your classes, methods, their parameters and their types using the standard reStructuredText syntax as supported by Sphinx, an example class is documented as follows:

class Example:
    **Example class**

    :param str param: A parameter
    :param bool : Source file name to compress
    :param list supported_zipper: List of supported compression tools
    :attr Optional[str] attr: A class attribute
    def __init__(self, param, param_w_default=False):
        self.attr = param if param_w_default else None

    def method(self, param):
        A method that takes a parameter.

        :param list param: a parameter
        :return: whether param is very long
        :rtype: bool
        return len(param) > 50

Try to stick to the following guidelines when documenting source code:

  • Classes should be documented directly in their main docstring and not in __init__.

  • Document every function parameter and every public attribute including their types.

  • Only public methods should be documented, private methods don’t have to, unless they are complex and it is not easy to grasp what they do (which should be avoided anyway).

Please also document any user-facing changes that you implementing (e.g. adding a new build type) in the user documentation, which can be found in doc/source. General documentation should be put into the working_with_kiwi/ subfolder, whereas documentation about more specialized topics would belong into the building/ subfolder.

Adhere to a line limit of 75 characters when writing the user facing documentation [1].

Additional Information

The following sections provides further information about the repository integrity, version, package and documentation management.

Signing Git Patches

To ensure the integrity of the repository and the code base, patches sent for inclusion should be signed with a GPG key.

To prepare Git to sign commits, follow these instructions:

  1. Create a key suitable for signing (it is not recommended to use existing keys to not mix it with your email environment):

    $ gpg2 --expert --full-gen-key
  2. Either choose a RSA key for signing (option (4)) or an ECC key for signing (option (10)). For a RSA key choose a key size of 4096 bits and for a ECC key choose Curve 25519 (option (1)). Enter a reasonable validity period (we recommend 2 to 5 years). Complete the key generation by entering your name and email address.

  3. Add the key ID to your git configuration, by running the following git config commands:

    $ git config --local user.signingkey $YOUR_SIGN_KEY_ID
    $ git config --local commit.gpgSign true

    Omitting the flag --local will make these settings global for all repositories (they will be added to ~/.gitconfig). You can find your signkey’s ID via:

    $ gpg2 --list-keys --keyid-format long $YOUR_EMAIL
    pub   rsa4096/AABBCCDDEEFF0011 2019-04-26 [S] [expires: 2021-04-16]
    uid                 [ultimate] YOU <$YOUR_EMAIL>

    The key’s ID in this case would be AABBCCDDEEFF0011. Note that your signkey will have only a [S] after the creation date, not a [SC] (then you are looking at your ordinary GPG key that can also encrypt).

Bumping the Version

The KIWI NG project follows the Semantic Versioning scheme. We use the bumpversion tool for consistent versioning.

Follow these instructions to bump the major, minor, or patch part of the KIWI NG version. Ensure that your repository is clean (i.e. no modified and unknown files exist) beforehand running bumpversion.

  • For backwards-compatible bug fixes:

    $ bumpversion patch
  • For additional functionality in a backwards-compatible manner. When changed, the patch level is reset to zero:

    $ bumpversion minor
  • For incompatible API changes. When changed, the patch and minor levels are reset to zero:

    $ bumpversion major

Creating a RPM Package

We provide a template for a RPM spec file in package/python-kiwi-spec-template alongside with a rpmlint configuration file and an automatically updated python-kiwi.changes.

To create the necessary files to build a RPM package via rpmbuild, run:

$ make build

The sources are collected in the dist/ directory. These can be directly build it with rpmbuild, fedpkg, or submitted to the Open Build Service using osc.