I have started using Amazon's new Launch Templates and so far liking it however I just recently made an image from one of my instances, I then created a new version of the Launch template and used the new AMI.
When updating my auto scaling group to the new version of the template, upon save it gives me the below error:
Error
You must use a valid fully-formed launch template. snapshotId cannot be modified on root device
Do I need to recreate the AMI?
Ok after a few tries I've discovered that the hint is in the error message as unclear as it was at the time. What I didn't do when creating the new version of the Launch Template was, after updating the AMI ID, I also needed to update the Snapshot ID of the volume used by the template, to the Snapshot ID of the snapshot created when the AMI was created.
Would help if when changing the AMI, it searched a list of existing AMIs then allowed you to select the one you want which will then update the template with the necessary things such as Snapshot ID...
c'est la vie