Either find the pid of the background process and send it a SIGHUP, or just start it again with -c reload (requires that the previously started daemon saves a PID file).
If you send the signals yourself instead of using -c, be sure you
hit the right process. There are usually two upsmon
processes, and you
should only send signals to one of them. To be safe, read the PID
file.
If your daemons are managed as systemd units, it is more idiomatic to
use the framework commands, e.g. systemctl reload nut-server
(upsd)
or systemctl reload nut-monitor
(upsmon). Note that the implementation
of nut-server.service
by default starts upsd -F
and does not save a
PID file; if your workflow requires to use plain upsd -c reload
, you
should customize the unit (with a drop-in file) to start upsd -FF
.
NUT releases after 2.8.0 define aliases for these units, so if your Linux
distribution uses NUT-provided unit definitions, systemctl reload upsd
may also work.