with shutting down plex and raspberry if runtime falls below 300 and 200 secs

README.md

@@ -829,12 +829,81 @@ The collector also sends an ntfy notification when:
 - Battery charge crosses below 50%
 - Battery charge crosses below 5%
 - Estimated battery runtime crosses below 5 minutes
+- Local Raspberry Pi shutdown is requested below 200 seconds of runtime
 
 Alert state is stored in `/var/lib/rrd/bx950mi-alert-state.json`, allowing
 changes to be detected across cron runs. The first run establishes a baseline
 without sending notifications. Threshold notifications can fire again after a
 value recovers above the threshold and later drops below it.
 
+### Automatic shutdown of the Plex server
+
+When the UPS status is `OB` or `LB` and estimated runtime is below five
+minutes, the collector requests a shutdown of `plex.local` over SSH as user
+`ups`. The request is sent once per outage. A failed SSH request is retried by
+the next cron run, while a return to `OL` resets the shutdown state.
+
+Generate a dedicated key on the UPS monitor:
+
+```bash
+sudo install -d -m 700 /opt/ups/.ssh
+sudo ssh-keygen -t ed25519 -f /opt/ups/.ssh/plex_shutdown -N ""
+sudo ssh-keyscan -H plex.local | sudo tee /opt/ups/.ssh/known_hosts
+sudo chmod 600 /opt/ups/.ssh/plex_shutdown /opt/ups/.ssh/known_hosts
+```
+
+Verify the scanned SSH host-key fingerprint against `plex.local` through a
+trusted channel before enabling automatic shutdown.
+
+On `plex.local`, create the restricted account and authorize shutdown:
+
+```bash
+sudo useradd --create-home --shell /bin/bash ups
+sudo visudo -f /etc/sudoers.d/ups-shutdown
+```
+
+Add this exact sudoers rule:
+
+```sudoers
+ups ALL=(root) NOPASSWD: /usr/sbin/shutdown -h now
+```
+
+Add the public key from `/opt/ups/.ssh/plex_shutdown.pub` to
+`/home/ups/.ssh/authorized_keys` on `plex.local`, prefixed with a forced command
+and SSH restrictions:
+
+```text
+restrict,command="sudo /usr/sbin/shutdown -h now" ssh-ed25519 AAAA... ups-shutdown
+```
+
+Verify SSH before relying on the automatic action:
+
+```bash
+sudo ssh -i /opt/ups/.ssh/plex_shutdown \
+  -o UserKnownHostsFile=/opt/ups/.ssh/known_hosts ups@plex.local
+```
+
+This test will shut down `plex.local`. The hostname, user, key, and known-hosts
+file can be overridden for the cron job with:
+
+```text
+UPS_SHUTDOWN_HOST
+UPS_SHUTDOWN_USER
+UPS_SHUTDOWN_KEY
+UPS_SHUTDOWN_KNOWN_HOSTS
+```
+
+### Automatic shutdown of the Raspberry Pi
+
+When UPS status is `OB` or `LB` and estimated runtime drops below 200 seconds,
+the collector sends an ntfy warning and requests shutdown of the Raspberry Pi
+running the script. It calls systemd-logind through D-Bus using the `dbus-next`
+Python package; it does not invoke a shell command.
+
+Because the collector runs from root's crontab, systemd-logind permits the
+power-off request. A failed request is retried by the next cron run, and the
+shutdown state resets after the UPS returns to `OL`.
+
 ---
 
 # 19. Testing the Python program