docs: info about cluster maintenance

Author: spwoodcock

docs/usage/cluster-maintenance.md

@@ -0,0 +1,17 @@
+# k8s Cluster Maintenance
+
+## Worker nodes disk filling up
+
+- The worker nodes pull images over time that they often
+  no longer need (e.g. app upgrades).
+- These images can fill up the disk space.
+- To clean them:
+  1. Access AWS EKS and go to Compute section.
+  2. Click on a node, then click through to the EC2 instance.
+  3. Connect using SSM Session Manager (the only option).
+  4. Run cleanup commands for containerd:
+
+  ```bash
+  sudo nerdctl image prune -a
+  sudo nerdctl system prune
+  ```

mkdocs.yml

@@ -60,6 +60,7 @@ nav:
   - Using The Cluster:
       - Connecting to the cluster: usage/connecting-to-cluster.md
       - Routing to the cluster: usage/routing-to-cluster-apps.md
+      - Cluster maintenance: usage/cluster-maintenance.md
   - Tutorials:
       - Intro to Kubernetes: tutorial/k8s-intro.md
       - Deploying Apps: tutorial/deploying-apps.md