Add migration scripts from RHOAI 2.x to RHOAI 3.x

scripts/migration/MIGRATION_GUIDE.md

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+# RHOAI RayCluster Migration Guide
+
+This guide walks you through migrating your RayClusters from RHOAI 2.x to RHOAI 3.x.
+
+## Overview
+
+The migration tool helps you:
+1. **Back up** your RayCluster configurations before the upgrade
+2. **Verify** your cluster is ready for the upgrade (automatic pre-flight checks)
+3. **Migrate** your RayClusters after the upgrade is complete
+
+The tool is designed to be safe and predictable:
+- **Staged approach**: Test on a single cluster before migrating everything
+- **Idempotent**: Safe to run multiple times
+- **Non-destructive**: Backups are created, nothing is deleted automatically
+
+---
+
+## Prerequisites
+
+### 1. Python Environment
+
+Python 3.6 or later is required.
+
+```bash
+python3 --version
+```
+
+### 2. Install Required Packages
+
+```bash
+pip install -r ray_cluster_migration_requirements.txt
+```
+
+Or install directly:
+
+```bash
+pip install kubernetes>=28.1.0 PyYAML>=6.0
+```
+
+### 3. Cluster Access
+
+Verify you can connect to your OpenShift cluster:
+
+```bash
+oc whoami
+oc get rayclusters --all-namespaces
+```
+
+---
+
+## Step 1: Pre-Upgrade (Before RHOAI Upgrade)
+
+Run the pre-upgrade command to verify prerequisites and back up your RayClusters:
+
+```bash
+python ray_cluster_migration.py pre-upgrade
+```
+
+The script will:
+1. Prompt for a backup directory (default: `./raycluster-backups`)
+2. Run automatic pre-flight checks (permissions, cert-manager, codeflare-operator status)
+3. Back up your RayCluster configurations
+
+**If any required checks fail, the script will stop and tell you exactly what needs to be fixed before you can proceed.**
+
+### Pre-Upgrade Options
+
+```bash
+# Back up a specific namespace only
+python ray_cluster_migration.py pre-upgrade --namespace my-namespace
+
+# Back up a single cluster (for testing)
+python ray_cluster_migration.py pre-upgrade --cluster my-cluster --namespace my-namespace
+
+# Specify backup directory directly
+python ray_cluster_migration.py pre-upgrade ./my-backup-directory
+```
+
+---
+
+## Step 2: Perform the RHOAI Upgrade
+
+Follow your standard RHOAI upgrade procedure to upgrade from RHOAI 2.x to RHOAI 3.x.
+
+---
+
+## Step 3: Post-Upgrade (After RHOAI Upgrade)
+
+After the RHOAI upgrade is complete, migrate your RayClusters.
+
+### Recommended: Staged Migration
+
+We recommend migrating in stages to verify everything works correctly:
+
+**Stage 1: Test with a single cluster**
+```bash
+# Preview first
+python ray_cluster_migration.py post-upgrade --cluster my-cluster --namespace my-namespace --dry-run
+
+# Run the migration
+python ray_cluster_migration.py post-upgrade --cluster my-cluster --namespace my-namespace
+```
+
+**Stage 2: Migrate a namespace**
+```bash
+python ray_cluster_migration.py post-upgrade --namespace my-namespace
+```
+
+**Stage 3: Migrate all remaining clusters**
+```bash
+python ray_cluster_migration.py post-upgrade
+```
+
+### Post-Upgrade Options
+
+```bash
+# Skip confirmation prompt (for automation)
+python ray_cluster_migration.py post-upgrade --yes
+
+# Preview changes without making them
+python ray_cluster_migration.py post-upgrade --dry-run
+```
+
+### Restore from Backup
+
+If your clusters were deleted during the upgrade or you prefer to restore from backup files:
+
+```bash
+# Restore all clusters from backup directory
+python ray_cluster_migration.py post-upgrade --from-backup ./raycluster-backups
+
+# Restore a single cluster from backup
+python ray_cluster_migration.py post-upgrade --from-backup ./raycluster-backups --cluster my-cluster --namespace my-namespace
+
+# Restore from a single backup file
+python ray_cluster_migration.py post-upgrade --from-backup ./raycluster-backups/raycluster-my-cluster-my-namespace.yaml
+```
+
+**Important:** `--from-backup` will **delete** any existing cluster with the same name before creating it from the backup. This ensures a clean restore.
+
+---
+
+## Check Migration Status
+
+Check which clusters need migration at any time:
+
+```bash
+python ray_cluster_migration.py list
+```
+
+---
+
+## Troubleshooting
+
+### Pre-flight check failed: cert-manager not detected
+
+Install cert-manager via OperatorHub in your OpenShift cluster:
+
+1. Go to OperatorHub in the OpenShift console
+2. Search for "cert-manager"
+3. Install the cert-manager operator
+4. Wait for it to be ready
+5. Run pre-upgrade again
+
+### Pre-flight check failed: codeflare-operator not Removed
+
+Update your DataScienceCluster:
+
+```bash
+oc patch datasciencecluster <dsc-name> --type merge -p '{"spec":{"components":{"codeflare":{"managementState":"Removed"}}}}'
+```
+
+### Migration failed for a cluster
+
+1. Check the error message for details
+2. Verify cluster health: `oc get raycluster <name> -n <namespace>`
+3. Retry just that cluster: `python ray_cluster_migration.py post-upgrade --cluster <name> --namespace <namespace>`
+
+### Route not available after migration
+
+Routes may take 30-60 seconds to be created. Check directly:
+
+```bash
+oc get httproute -n <namespace>
+```
+
+---
+
+## Quick Reference
+
+```bash
+# Before RHOAI upgrade
+python ray_cluster_migration.py pre-upgrade
+
+# After RHOAI upgrade (staged approach)
+python ray_cluster_migration.py post-upgrade --cluster test-cluster --namespace dev --dry-run
+python ray_cluster_migration.py post-upgrade --cluster test-cluster --namespace dev
+python ray_cluster_migration.py post-upgrade --namespace dev
+python ray_cluster_migration.py post-upgrade
+
+# Check status anytime
+python ray_cluster_migration.py list
+```
+
+## Command Reference
+
+| Command | Description |
+|---------|-------------|
+| `pre-upgrade` | Run pre-flight checks and backup RayClusters |
+| `post-upgrade` | Migrate RayClusters after RHOAI upgrade |
+| `list` | Show all RayClusters and their migration status |
+| `delete` | [Advanced] Delete RayClusters |
+| `import` | [Advanced] Restore RayClusters from backup |
+
+### Common Options
+
+| Option | Description |
+|--------|-------------|
+| `--cluster NAME` | Target a specific cluster (requires `--namespace`) |
+| `--namespace NS` | Target a specific namespace |
+| `--dry-run` | Preview changes without applying them |
+| `--yes` | Skip confirmation prompts |
+| `--from-backup PATH` | (post-upgrade only) Restore from backup file or directory. Deletes existing clusters before recreating. |