[Backport 3.2] Add a patch and upgrade guide for MA

_migration-assistant/security-patching-and-updating.md

@@ -0,0 +1,90 @@
+---
+layout: default
+title: Security patching & updating
+nav_order: 30
+parent: Migration Assistant for OpenSearch
+permalink: /migration-assistant/security-patching-and-updating/
+---
+
+# Security patching and updating
+
+This page describes how to safely update the **bootstrap box** (the Amazon Elastic Compute Cloud [Amazon EC2] instance you use to build and run Migration Assistant components), clean Docker caches, and rebuild the Migration Assistant container images.
+
+> **Recommended cadence**: Perform these steps only when Migration Assistant is not actively running.
+
+---
+
+## Step 1: Patch the OS on the bootstrap box
+
+```shell
+sudo dnf upgrade --refresh -y
+```
+{% include copy.html %}
+
+> **Note**: If the kernel or core libraries are updated, a reboot is often required.
+
+Reboot if required:
+
+```shell
+sudo reboot
+```
+{% include copy.html %}
+
+After the box comes back up, reconnect and continue.
+
+
+## Step 2: Clear Docker build and download caches
+
+Clearing the Docker build and downloaded caches removes **all** unused images, containers, networks, and volumes to free disk space and ensure clean rebuilds:
+
+```shell
+docker system prune -a --volumes
+```
+{% include copy.html %}
+
+
+## Step 3: Clean prior Gradle outputs
+
+From the repository root, run the following command to clean prior Gradle outputs:
+
+```shell
+./gradlew clean
+```
+{% include copy.html %}
+
+
+## Step 4: Rebuild Migration Assistant images
+
+Rebuild the Docker images used by Migration Assistant:
+
+```shell
+./gradlew :buildDockerImages -x test
+```
+{% include copy.html %}
+
+
+## Step 5: Redeploy Migration Assistant
+
+Redeploy Migration Assistant to replace existing container images with the freshly built versions:
+
+```shell
+cd deployment/cdk/opensearch-service-migration
+./deploy.sh <contextId>
+```
+{% include copy.html %}
+
+> **Warning**: Redeployment will interrupt any running migration tasks (for example, Capture Proxy, Traffic Replayer, or Reindex-from-Snapshot).
+> **Do not** redeploy while actively migrating, as this can cause data loss or inconsistent state.
+{: .warning}
+
+
+## Troubleshooting
+
+* **`toomanyrequests: Rate exceeded`**:
+  Retry the last build command. Some downstream container images are rate limited and may change over time.
+
+* **Cannot pull base images**:
+  Ensure that the instance has internet egress (NAT/IGW) and access to Docker Hub/Amazon Elastic Container Registry (Amazon ECR) as required.
+
+* **Gradle cache corruption**:
+  If problems persist after `./gradlew clean`, also remove `~/.gradle/caches` and retry.