From start to removal.
WHAT THE STATES ARE
Created Running Paused Stopped Removed
WHAT HAPPENS ON START
The runtime creates namespaces, applies limits, mounts the filesystem, and executes the command.
WHAT THE COMMAND IS
The entry point, plus any arguments.
WHAT PROCESS IDENTIFIER ONE MEANS
Your process is the first process in its namespace.
WHY THAT MATTERS
That position carries responsibilities: reaping child processes, and handling signals.
WHAT HAPPENS IF IT DOES NOT
Zombie processes accumulate Termination signals are ignored, so shutdown takes the full grace period
WHAT TO DO ABOUT IT
Use an init process as the entry point, or handle signals properly.
WHAT SHELL FORM VERSUS EXECUTABLE FORM CHANGES
Shell form wraps the command in a shell, which becomes process one.
WHAT THAT BREAKS
Signal delivery to your application.
WHAT TO USE
The executable form, so your process receives signals directly.
WHAT HAPPENS ON STOP
A termination signal, a grace period, then a forced kill.
WHAT TO DO IN THAT WINDOW
Stop accepting work, finish what is in progress, exit.
WHAT HAPPENS ON REMOVAL
The writable layer is deleted.
WHAT SURVIVES
Volumes, and anything written outside.
