monitoring: restore README

services/monitoring/README.md

@@ -0,0 +1,28 @@
+# services/monitoring
+
+## Grafana admin secret
+
+The Grafana Helm release expects a pre-existing secret named `grafana-admin`
+in the `monitoring` namespace. Create or rotate it with:
+
+```bash
+kubectl create secret generic grafana-admin \
+  --namespace monitoring \
+  --from-literal=admin-user=admin \
+  --from-literal=admin-password='REPLACE_ME'
+```
+
+Update the password whenever you rotate credentials.
+
+## DCGM exporter image
+
+The NVIDIA GPU metrics DaemonSet expects `registry.bstein.dev/monitoring/dcgm-exporter:4.4.2-4.7.0-ubuntu22.04`, mirrored from `docker.io/nvidia/dcgm-exporter:4.4.2-4.7.0-ubuntu22.04`. Refresh it in Zot when bumping versions:
+
+```bash
+skopeo copy \
+  --all \
+  docker://docker.io/nvidia/dcgm-exporter:4.4.2-4.7.0-ubuntu22.04 \
+  docker://registry.bstein.dev/monitoring/dcgm-exporter:4.4.2-4.7.0-ubuntu22.04
+```
+
+When finished mirroring from the control-plane, you can remove temporary tooling with `sudo apt-get purge -y skopeo && sudo apt-get autoremove -y` and clear `~/.config/containers/auth.json`.