kill

Additional Notes

kill sends signals to processes. Despite the name, it does not only kill processes. It can request termination, force termination, reload configuration, pause, continue, or send other signals.

The most common workflow is to find a process ID with ps, pgrep, or top, then send a signal with kill.

Syntax

kill [signal] PID...

Parameters

• PID: Process ID to signal.
• signal: Signal name or number. If omitted, kill sends TERM.

Common Signals

• TERM or 15: Ask a process to terminate gracefully. This is the default.
• KILL or 9: Force the kernel to terminate the process. The process cannot clean up.
• HUP or 1: Hangup. Many daemons use this to reload configuration.
• INT or 2: Interrupt, similar to pressing Ctrl+C.
• STOP: Pause a process.
• CONT: Continue a stopped process.

Examples

kill 1234

Ask process 1234 to terminate.

kill -TERM 1234

Same as the default: graceful termination request.

kill -9 1234

Force-kill a process.

kill -HUP 1234

Send hangup, often used to reload daemon configuration.

kill -STOP 1234
kill -CONT 1234

Pause and continue a process.

kill -l

List available signals.

Practical Notes

• Try normal kill PID before kill -9 PID.
• kill -9 prevents cleanup, so temporary files, locks, or child processes may remain.
• You can usually signal only your own processes unless you use sudo.
• Use pkill or killall when you want to signal by process name.
• Always confirm the PID before signaling an important process.