You edited a daemon's configuration file and want the running daemon to reread it without restarting. Which signal is conventionally used?
LPIC-1 Exam 101-500, objective 103. GNU and Unix commands medium
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The options
Not correct SIGKILL (9)
Wrong. SIGKILL forcibly terminates the process with no handler and no cleanup — the opposite of a graceful reload.
Not correct SIGTERM (15)
Wrong. SIGTERM is the standard request to shut down. The daemon would exit, not reload.
Correct SIGHUP (1)
Correct. By convention many daemons trap SIGHUP and reload their configuration, keeping their PID and open sockets.
Not correct SIGCONT
Wrong. SIGCONT resumes a process that was stopped by SIGSTOP or SIGTSTP. It has nothing to do with configuration.
Why
SIGHUP (1) meant 'the terminal hung up', and because daemons have no terminal the signal was repurposed as 'reload your configuration'. It is a convention, not a kernel rule: a program only reloads if its author wrote a handler, so check the daemon's documentation.
Where this comes from
- Cited
- LPI exam objective 103.5
- What it says
- Common signal names and numbers and their usual meanings.
Practise this
Reading one question is not practice. The trainer will draw a set from objective 103 and space the ones you get wrong.