This chapter will get you started with Borg development.

Borg is written in Python (with a little bit of Cython and C for the performance critical parts).


... are welcome!

Some guidance for contributors:

  • discuss about changes on github issue tracker, IRC or mailing list
  • choose the branch you base your changesets on wisely:
    • choose x.y-maint for stuff that should go into next x.y.z release (it usually gets merged into master branch later also), like:
      • bug fixes (code or docs)
      • missing important (and preferably small) features
      • docs rearrangements (so stuff stays in-sync to avoid merge troubles in future)
    • choose master if that does not apply, like for:
      • developing new features
  • do clean changesets:
    • focus on some topic, resist changing anything else.
    • do not do style changes mixed with functional changes.
    • try to avoid refactorings mixed with functional changes.
    • if you need to fix something after commit/push:
      • if there are ongoing reviews: do a fixup commit you can merge into the bad commit later.
      • if there are no ongoing reviews or you did not push the bad commit yet: edit the commit to include your fix or merge the fixup commit before pushing.
    • have a nice, clear, typo-free commit comment
    • if you fixed an issue, refer to it in your commit comment
    • follow the style guide (see below)
  • if you write new code, please add tests and docs for it
  • run the tests, fix anything that comes up
  • make a pull request on github
  • wait for review by other developers

Style guide

We generally follow pep8, with 120 columns instead of 79. We do not use form-feed (^L) characters to separate sections either. Compliance is tested automatically when you run the tests.

Continuous Integration

All pull requests go through Travis-CI, which runs the tests on Linux and Mac OS X as well as the flake8 style checker. Additional Unix-like platforms are tested on Golem.

Output and Logging

When writing logger calls, always use correct log level (debug only for debugging, info for informative messages, warning for warnings, error for errors, critical for critical errors/states).

When directly talking to the user (e.g. Y/N questions), do not use logging, but directly output to stderr (not: stdout, it could be connected to a pipe).

To control the amount and kinds of messages output to stderr or emitted at info level, use flags like --stats or --list.

Building a development environment

First, just install borg into a virtual env as described before.

To install some additional packages needed for running the tests, activate your virtual env and run:

pip install -r requirements.d/development.txt

Running the tests

The tests are in the borg/testsuite package.

To run all the tests, you need to have fakeroot installed. If you do not have fakeroot, you still will be able to run most tests, just leave away the fakeroot -u from the given command lines.

To run the test suite use the following command:

fakeroot -u tox  # run all tests

Some more advanced examples:

# verify a changed tox.ini (run this after any change to tox.ini):
fakeroot -u tox --recreate

fakeroot -u tox -e py34  # run all tests, but only on python 3.4

fakeroot -u tox borg.testsuite.locking  # only run 1 test module

fakeroot -u tox borg.testsuite.locking -- -k '"not Timer"'  # exclude some tests

fakeroot -u tox borg.testsuite -- -v  # verbose py.test

Important notes:

  • When using -- to give options to py.test, you MUST also give borg.testsuite[.module].

Regenerate usage files

Usage and API documentation is currently committed directly to git, although those files are generated automatically from the source tree.

When a new module is added, the docs/api.rst file needs to be regenerated:

./ build_api

When a command is added, a commandline flag changed, added or removed, the usage docs need to be rebuilt as well:

./ build_usage

Building the docs with Sphinx

The documentation (in reStructuredText format, .rst) is in docs/.

To build the html version of it, you need to have sphinx installed:

pip3 install sphinx sphinx_rtd_theme  # important: this will install sphinx with Python 3

Now run:

cd docs/
make html

Then point a web browser at docs/_build/html/index.html.

The website is updated automatically through Github web hooks on the main repository.

Using Vagrant

We use Vagrant for the automated creation of testing environments and borgbackup standalone binaries for various platforms.

For better security, there is no automatic sync in the VM to host direction. The plugin vagrant-scp is useful to copy stuff from the VMs to the host.


# To create and provision the VM:
vagrant up OS
# To create an ssh session to the VM:
vagrant ssh OS command
# To shut down the VM:
vagrant halt OS
# To shut down and destroy the VM:
vagrant destroy OS
# To copy files from the VM (in this case, the generated binary):
vagrant scp OS:/vagrant/borg/borg.exe .

Creating standalone binaries

Make sure you have everything built and installed (including llfuse and fuse). When using the Vagrant VMs, pyinstaller will already be installed.

With virtual env activated:

pip install pyinstaller  # or git checkout master
pyinstaller -F -n borg-PLATFORM borg/
for file in dist/borg-*; do gpg --armor --detach-sign $file; done

If you encounter issues, see also our Vagrantfile for details.


Standalone binaries built with pyinstaller are supposed to work on same OS, same architecture (x86 32bit, amd64 64bit) without external dependencies.

Creating a new release


  • make sure all issues for this milestone are closed or moved to the next milestone

  • find and fix any low hanging fruit left on the issue tracker

  • check that Travis CI is happy

  • update CHANGES.rst, based on git log $PREVIOUS_RELEASE..

  • check version number of upcoming release in CHANGES.rst

  • verify that and are complete

  • python build_api ; python build_usage and commit

  • tag the release:

    git tag -s -m "tagged/signed release X.Y.Z" X.Y.Z
  • create a clean repo and use it for the following steps:

    git clone borg borg-clean

    This makes sure no uncommitted files get into the release archive. It also will find if you forgot to commit something that is needed. It also makes sure the vagrant machines only get committed files and do a fresh start based on that.

  • run tox and/or binary builds on all supported platforms via vagrant, check for test failures

  • create a release on PyPi:

    python register sdist upload --identity="Thomas Waldmann" --sign
  • close release milestone on Github

  • announce on:

  • Mailing list
  • Twitter (follow @ThomasJWaldmann for these tweets)
  • IRC channel (change /topic)
  • create a Github release, include:
    • standalone binaries (see above for how to create them)
      • for OS X, document the OS X Fuse version in the README of the binaries. OS X FUSE uses a kernel extension that needs to be compatible with the code contained in the binary.
    • a link to CHANGES.rst