5.) Instead of init.d scripts create systemd units. https://wiki.debian.org/systemd#Creating_or_altering_services
https://freedesktop.org/wiki/Software/systemd/ About your gitlab-runner.service failure: https://wiki.debian.org/systemd#Failed_units HINT: Extensive debugging information about systemd is on this FreeDesktop page. https://freedesktop.org/wiki/Software/systemd/Debugging/ What is in gitlab-runner.service on that one server anyways? Somewhen in 2016-2018 someone on debian planet posted multiple blogs of a great systemd introduction series, I can't find my bookmark right now :( Peter
