The kill command sends signals to processes. To force the termination of a non-responsive process, the SIGKILL signal (signal number 9) should be used. This signal cannot be caught or ignored by the process, and the kernel will terminate it immediately. The default kill command and kill -15 both send SIGTERM, which is a request for graceful termination that a non-responsive process might ignore. Signal 1 (SIGHUP) is typically used to signal a daemon to reload its configuration.

A. kill PID sends the default SIGTERM (15) signal, which requests a graceful shutdown and can be ignored by a non-responsive process.

B. kill -1 PID sends the SIGHUP signal, which is typically used to have a daemon re-read its configuration file, not terminate it.

D. kill -15 PID explicitly sends the SIGTERM signal, which is the same as the default and is not a forced termination.

1. GNU Coreutils. (2022). kill invocation. In GNU Coreutils manual. Section 23.2. Retrieved from https://www.gnu.org/software/coreutils/manual/htmlnode/kill-invocation.html (Describes signal numbers and their meanings

including SIGKILL as 9).

2. Red Hat Enterprise Linux 9 Documentation. (2023). Chapter 9. Managing processes. Section 9.3.2. Terminating processes. Retrieved from https://access.redhat.com/documentation/en-us/redhatenterpriselinux/9/html/configuringbasicsystemsettings/managing-processesconfiguring-basic-system-settings (Specifies that kill -9 sends the SIGKILL signal to immediately stop a process).

3. Bovet

D. P.

& Cesati

M. (2005). Understanding the Linux Kernel

3rd Edition. O'Reilly Media. Chapter 10

Signals

p. 405. (Explains that SIGKILL and SIGSTOP are two special signals that cannot be caught or ignored).