SIGHUP

Signal 1. Its default action is to terminate: "re-read your configuration" is only a convention some daemons opted into, and a program that arranged for neither meaning dies. The shell reports Hangup, and the lock file it held stays on disk exactly as -9 would have left it. The literal meaning came first — the kernel sends SIGHUP when a controlling terminal goes away, which is why a job started with a bare & over SSH dies with the session. A unit answers systemctl reload only because somebody wrote a reload line into it, often a kill -s HUP aimed at the main process; without that line, no signal reloads anything. Write -s HUP rather than kill -1, which reads like a typing mistake.