I'm curious about what happens when a Linux process is terminated either nicely or abruptly. For example, if I'm running a Python script (`my_script.py`) and it finishes without any errors, is there a specific sequence that the process goes through to close down? And in the case where my script is running for a long time and the machine is rebooted unexpectedly by an admin, what consequences would that have? If the machine shuts down immediately, is that the same as a power failure? Additionally, if the program is running in a Tmux or Screen session, would it still close down gracefully?
1 Answer
You’re really getting into the details of process management! When a process is closed nicely, it typically receives a SIGTERM signal (signal 15), which allows it to perform cleanup tasks like saving data, closing files, or ending connections properly. On the other hand, closing abruptly with a SIGKILL signal (signal 9) gives no such opportunity—it's just cut off immediately. In scenarios 2 and 3, when a machine reboots, it'll usually send out the SIGTERM first to allow processes to quit nicely before it resorts to SIGKILL if they don’t respond. If you're running in Tmux, it depends on whether Tmux itself is closed gracefully or not, but the process can still receive termination signals depending on how it's set up.
But if the machine loses power suddenly, wouldn’t no signal be sent?