[Unit]
Description=Prometheus Server
After=network-online.target
[Service]
User=prometheus
Restart=on-failure
RestartSec=5
TimeoutStopSec=300
WorkingDirectory=/opt/prometheus
EnvironmentFile=/etc/default/prometheus
ExecStart=/opt/prometheus/prometheus $OPTIONS
ExecReload=/bin/kill -HUP $MAINPID
[Install]
WantedBy=multi-user.target
and then "systemctl reload prometheus" will reload the config (without doing a full restart)