Merge pull request #5500 from ministryofjustice/add-ami-launch-templa…

…te-info

Add runbook on upgrading AMI versions

runbooks/source/upgrade-AMI-version.html.md.erb

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+---
+title: Upgrade AMI Version
+weight: 53
+last_reviewed_on: 2024-04-22
+review_in: 6 months
+---
+
+# Upgrade AMI Version
+
+AWS releases new AMI versions for EKS node groups that include Kubernetes patches and security updates. To upgrade the node groups to use the new AMI version:
+
+- login to the AWS console
+- Select EKS and select the cluster
+- Select the node group and click on `Update AMI version`
+- Select the Update Strategy to "Force update" and click on "Update"
+
+This will perform a rolling update of all the nodes in the node group. Follow the steps in [Recycle all nodes](#recycle-all-nodes) section to recycle all the nodes.
+
+# Recycle all nodes
+
+When a node group version changes, this will cause all of the nodes to recycle. When AWS recycles the nodes, it will not evict pods if it will break the PDB.
+This will cause the node to stall the update and the nodes will **not** continue to recycle.
+
+To rectify this, run the script mentioned in [Recycle-all-nodes- Gotchas](/recycle-all-nodes.html#gotchas) section.