Patching OS in Auto Scaling Groups with Rolling Updates

• A.Update the AMI used by the Auto Scaling group launch configuration and manually terminate all running instances.
• ✓ B.Create a new launch configuration with an updated AMI and perform a rolling update using the Auto Scaling group.
• C.Update the AMI and stop the Auto Scaling group, then start it again.
• D.Install patches on each running instance using AWS Systems Manager Patch Manager.

Why B: Option B is correct because a rolling update replaces instances gradually, maintaining capacity. Option A is wrong because it does not address replacement. Option C is wrong because it causes downtime. Option D is wrong because it does not apply to running instances.

• A.Create a custom AMI and manually terminate each instance to launch new ones.
• B.Stop all instances, apply the patch using a script, and restart them.
• C.Use AWS Systems Manager Patch Manager to apply the patch to all instances simultaneously.
• ✓ D.Create a new AMI with the patch applied, update the launch template, and perform a rolling update via Auto Scaling.

Why D: Option D is the most efficient and minimizes downtime because it uses a rolling update strategy. By creating a new AMI with the patch applied and updating the launch template in the Auto Scaling group, instances are gradually replaced without stopping all at once. Option A is incorrect because manually terminating instances is not efficient and doesn't leverage Auto Scaling automation. Option B is incorrect because stopping all instances to apply a patch causes downtime. Option C is incorrect because while Systems Manager Patch Manager can apply patches, simultaneous patching without a rolling update risks service disruption, especially if reboots are required. The rolling update via Auto Scaling ensures high availability.

• ✓ A.Create a new AMI with the patch applied, update the launch configuration, and perform a rolling update using an Auto Scaling lifecycle hook.
• B.Update the launch configuration with the patched AMI and manually terminate running instances.
• C.Stop the Auto Scaling group, patch the instance, and restart the group.
• D.SSH into each instance and apply the patch manually.

Why A: Option A is the best practice because it leverages a lifecycle hook to perform a rolling update, replacing old instances with new ones based on a patched AMI without downtime. This approach ensures that each instance is gracefully terminated after a new instance is ready. Option B is incorrect because simply updating the launch configuration and manually terminating instances can cause downtime and is not automated. Option C is incorrect because stopping the Auto Scaling group and patching in place leads to downtime and is not scalable. Option D is incorrect because applying patches manually via SSH is error-prone and requires sequential instance patching, causing downtime.