There may be times during an upgrade or other maintenance when it is best to have Jenkins start, but not launch any projects. For example, if an upgrade is being performed in multiple steps, the intermediate steps may not be fully configured to run projects successfully. The "quiet start plugin" can immediately place the Jenkins server in "quieting down" state on startup.
This requires the installation of the CloudBees Quiet Start Plugin plugin.
Enable "quiet start" by checking the box in. When the server is restarted, it will be in the "quieting down" state. An administrator can cancel that state using the regular UI.
Uncheck the box inwhen maintenance is complete. Projects will start as usual on server restart.
Using the CloudBees Quiet Start Plugin