What signal is sent when using the kill command: SIGTERM or SIGKILL?

When using the kill command without specifying a signal number or name, the default signal sent is SIGTERM.

SIGTERM (Terminate Signal):

• This is a gentle termination signal.
• It requests the process to terminate gracefully.
• The process can catch this signal, perform cleanup (close files, save state), and then exit, or ignore it.

SIGKILL (Kill Signal):

• This is a "hard" termination signal.
• It cannot be caught or ignored by the process.
• The system immediately terminates the process without giving it a chance to clean up.

Thus, kill by default sends SIGTERM. To send SIGKILL, you need to specify it explicitly:

# Send SIGTERM (default)
kill <PID>

# Send SIGKILL
kill -9 <PID>
# or
kill -s SIGKILL <PID>