| name | mgn-diagnostics |
| version | 1.0.0 |
| last_updated | 2025-04-12 |
| description | Use this skill to investigate and troubleshoot AWS Application Migration Service (MGN) problems by analyzing source server registration, replication status, launch templates, cutover operations, post-migration validation, agent installation, and following structured runbooks. Activate when: source server not replicating, replication lag, launch failures, cutover errors, post-migration issues, agent problems, or the user says something is wrong with MGN without naming specific symptoms.
|
| compatibility | Requires AWS CLI or SDK access with mgn, ec2, iam, cloudtrail, and ssm permissions. MGN requires source servers with the AWS Replication Agent installed.
|
AWS Application Migration Service Diagnostics
When to use
Any AWS MGN investigation where the console alone is insufficient — source server registration, replication issues, launch template errors, cutover failures, post-migration validation, or agent installation problems.
Investigation workflow
Step 1 — Collect and triage
aws mgn describe-source-servers --query 'items[*].{Id:sourceServerID,Hostname:sourceProperties.identificationHints.hostname,State:lifeCycle.state,Replication:dataReplicationInfo.dataReplicationState}'
version: "1.0.0"
last_updated: "2025-04-12"
aws mgn describe-replication-configuration-templates
aws mgn describe-launch-configuration-templates
Step 2 — Domain deep dive
aws mgn describe-source-servers --filters 'sourceServerIDs=<id>' --query 'items[0].dataReplicationInfo'
aws mgn get-launch-configuration --source-server-id <id>
aws mgn get-replication-configuration --source-server-id <id>
aws mgn describe-jobs --filters 'fromDate=2024-01-01T00:00:00Z'
Step 3 — Detailed investigation
aws cloudtrail lookup-events --lookup-attributes AttributeKey=EventSource,AttributeValue=mgn.amazonaws.com --max-results 20
aws mgn describe-job-log-items --job-id <job-id>
aws mgn list-waves
aws mgn list-applications
Read references/guardrails.md before concluding on any MGN issue.
Tool quick reference
| Tool / API | When to use |
|---|
mgn describe-source-servers | Check source server status |
mgn get-replication-configuration | Review replication settings |
mgn get-launch-configuration | Review launch settings |
mgn describe-jobs | List migration jobs |
mgn start-cutover | Initiate cutover |
mgn finalize-cutover | Finalize migration |
mgn list-waves | List migration waves |
mgn list-applications | List migration applications |
Gotchas: AWS Application Migration Service
- MGN and DRS share the same replication agent. A source server can only be registered with ONE service at a time (MGN or DRS, not both).
- Cutover is a multi-step process: StartCutover → validate → FinalizeCutover. Finalizing cutover stops replication permanently. This is irreversible.
- Waves and Applications are organizational constructs for grouping servers. They don't affect replication or launch behavior directly.
- Post-launch actions use SSM Run Command. The recovery instance must have SSM agent and connectivity to SSM endpoints.
- MGN is being superseded by DRS for some use cases. Check current AWS recommendations for new migrations.
- Launch template changes don't retroactively apply to existing source servers.
Anti-hallucination rules
- Always cite specific source server IDs, replication states, or API responses as evidence.
- MGN agent is the same as DRS agent. Never suggest installing both.
- FinalizeCutover is irreversible — it stops replication permanently. Never omit this warning.
- Waves/Applications are organizational only. Never claim they affect replication.
- Spend no more than 2 minutes on any single hypothesis. Pivot if inconclusive.
14 runbooks
| Category | IDs | Covers |
|---|
| A — Source Server | A1-A2 | Registration, source properties |
| B — Replication | B1-B3 | Replication lag, stalled replication, initial sync |
| C — Launch Template | C1-C2 | Launch errors, instance mapping |
| D — Cutover | D1-D3 | Cutover launch, cutover finalization, rollback |
| E — Post-Migration | E1-E2 | Validation, application testing |
| F — Agent | F1-F2 | Agent installation, agent connectivity |
| Z — Catch-All | Z1 | General troubleshooting |
