Error message
In the message, %s marks a value that the engine fills in when it raises the error.
The story
A process tried to control another process that is not its child, and the engine said no. The rule is about family. Whoever creates a process becomes its parent, and the engine records that. A parent can reboot, stop, kill, vanish or resurrect its children. But it cannot touch its neighbor, a process it did not create. Think of a manager who can dismiss people on their own team, but cannot walk into the next department and fire someone there. Every lifecycle verb checks this relationship first. And not only neighbors are refused. A process acting on itself is refused, and so is a process acting on its own parent, or on any process it did not mint. The engine never obeys these quietly. The message gives you the verb and the address you wrote. The fix: only act on processes that you created yourself, using the identifier that process new gave you. If another process needs to be stopped, ask its own parent to do it.
Text from the Rush engine's error catalogue.