Most of the integration tests have been made to not write to /usr but some genuinely need to do so. Because mkosi creates images with a read-only /usr it is not normally writeable. By mounting an overlayfs with /usr as the lower dir and upper and working dirs in /var tests may write to /usr.
System and Service Manager
Details
Most documentation is available on systemd's web site.
Assorted, older, general information about systemd can be found in the systemd Wiki.
Information about build requirements is provided in the README file.
Consult our NEWS file for information about what's new in the most recent systemd versions.
Please see the Code Map for information about this repository's layout and content.
Please see the Hacking guide for information on how to hack on systemd and test your modifications.
Please see our Contribution Guidelines for more information about filing GitHub Issues and posting GitHub Pull Requests.
When preparing patches for systemd, please follow our Coding Style Guidelines.
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Stable branches with backported patches are available in the stable repo.
