I make fairly extensive use of systemd for scripting tasks which I need to run repeatedly and possibly on schedule (or based on other triggers), and recording a log of the output. At work and among friends, people use Jenkins for the same purpose. This gave me a stupid idea - can I turn systemd into Jenkins, and use it to build Git codebases?

Disclaimer: This is purely a bit of “what if?” fun, not serious advice

The basic idea is quite simple

  1. Write a timer to pull a git repo
  2. If a new change is found, trigger a oneshot service to build the project

Writing this for each project would get quite repetitive, so I’d like to generify it as follows

  1. The timer will be parameterised with the git URL, so I can do systemctl enable systemd-ci-poll@$REPO
  2. The builder service will expect an executable at $REPO/.systemd-ci/build


Since this is just a proof of concept, I make the followingg assumptions

  1. Every project has a name marching [a-Z0-9]+, to saves character escaping headaches
  2. Every project is already cloned in the workspace dir, and we’re only building the branch that’s been checked out
  3. I’m not including any sort of artefact archiving or workspace cleaning. That could be implemented if needed, but for this PoC I’ll take the laissez-faire approach of leaving that to the build script
  4. We can always fast-forward. No force pushes!

System setup

I deployed a fresh Ubuntu 20.04 LTS Linux container on Proxmox and made the following changes

  • Installed git
  • Add a systemd-ci user and group with the normal minimal permissions expected of a service user
  • Create the workspace dir /var/lib/systemd-ci with owner systemd-ci:systemd-ci and mode 770

The builder service

This service is quite simple - just run an executable


Description=Build a systemd-ci project


We can test this in isolation, by just creating

/var/lib/systemd-ci/test/.systemd-ci/build (mode: +x)

#!/bin/bash -eux
touch success
echo it works

Then execute systemctl start systemd-ci-build@test (remembering to do a daemon-reload first). Logs can be found with journalctl -u systemd-ci-build@test

The trigger service

So for the timer, we need to repeatedly pull the repository, and take note of when it changes. In accordance with assumption 4, let’s be really hacky and just grep Fast-forward in the git output


Description=Poll a systemd-ci project repo and trigger a build if necessary

ExecStart=/bin/bash -c "git pull | grep Fast-forward"

And here we run into a problem. OnSuccess was added in systemd 249, but this version of Ubuntu has 245. Luckily, bash has a negation operator, so I can use OnFailure and ExecStart=/bin/bash -c "! git...

The polling timer


Description=Run a systemd-ci poll every 15m



As far as I understand you need to enable systemd-ci-poll@.timer at least once, in addition to systemd-ci-poll@$REPO.timer. Well, I guess that provides an easy way to turn the whole thing off if needed

Project creation script

systemd-ci-init (mode +x)

#!/bin/bash -eux

# Syntax: sudo systemd-ci-init <repo url> <project name>

cd /var/lib/systemd-ci
git clone $1 $2
chown -R systemd-ci:systemd-ci $2
systemctl enable --now systemd-ci-poll@.timer
systemctl enable --now systemd-ci-poll@$2.timer


Yes, you can do it, no, you probably shouldn’t. The main problem is that you pollute the logs with “failed” polls, but I imagine this can be fixed if one is determined enough, but not on version 245