Which pair of signals correspond to immediate termination and graceful shutdown respectively?

• A. SIGKILL (-9) and SIGTERM (-15)
• B. SIGINT (-2) and SIGTERM (-15)
• C. SIGHUP (-1) and SIGTERM (-15)
• D. SIGSTOP (-19) and SIGCONT (-18)

Answer: (A)

Signals control how the system can terminate or pause a process. For immediate termination, you want something the process cannot catch or ignore, and that is SIGKILL. It forces the kernel to end the process right away, with no chance to run cleanup code.

For a graceful shutdown, you want a signal that the process can handle to perform its cleanup tasks—close files, flush buffers, release resources—before exiting. That signal is SIGTERM, which requests termination but allows the process to exit cleanly if it handles or responds to it.

So, the pair that matches immediate termination and graceful shutdown is SIGKILL for the immediate end and SIGTERM for a controlled, orderly shutdown. Other signals listed don’t map as cleanly to those behaviors: SIGINT is an interrupt that can be handled; SIGHUP is a hangup often used to trigger config reloads; SIGSTOP and SIGCONT stop and resume execution rather than terminate.