Controls whether the module may directly save changes to package-managed unit files from vendor directories such as /usr/lib/systemd/system or /lib/systemd/system. This is disabled by default because package updates may overwrite or depend on those files.

When set to no, packaged unit files can still be inspected in the manual editor when vendor files are included, but they are read-only. Use drop-in overrides or local units under /etc/systemd/system for normal customization.