This is the easiest way (I think) to switch your Windows AMI licensing type from BYOL to AWS

• Personal experience

• Not official

aws ec2 import-image --license-type [BYOL|AWS]

• Above is the cli import your image to an AWS AMI.

• If you not sure your AMI is BYOL or AWS, there still some ways to determine,

• • When you using aws ec2 import-image cli, there is a parameter called --license-type, it's BYOL by default. Unfortunately, there is no further way to see or change the property again.
• • Launch a 2012 instance, see if the instance is activated by AWS KMS 169.254.169.250:1688 or 169.254.169.251:1688, if yes, your AMI is AWS managed license, to double confirm, you can run slmgr /rearm to clear activation status and reboot see if the instance is activated again. This by default is a automatic behivor controlled by ec2config service, you can see its logs in C:\Program Files\Amazon\Ec2ConfigService\Logs\Ec2ConfigLog.log to know how it works. Below is a peice of logs shows this instance is launched from a BYOL AMI, so ec2config didn't activate it.

Ec2WindowsActivate: Ec2WindowsActivate plugin has skipped activation since instance will be configured with BYOL.

• As for 2016, ec2config is replaced by ec2launch, I didn't put much attention yet, however it still can be confirmed by AWS KMS hosts in most cases.

Then, how to switch from BYOL to AWS and keep all my customnized OS settings?

• There is no official way to do it as I know so far.

• You can run aws ec2 import-image --license-type AWS to import your image again. Or, use following trick.

Trick

• Go to instance page, launch an instance from your BYOL AMI, refer as i-BYOL, from ec2config logs you can see Ec2WindowsActivate didn't work because it's BYOL

• Do nothing and shutdown i-BYOL

• Go to volume page, find the volume of i-BYOL and detach, refer as vol-BYOL

• Now you can terminate i-BYOL and delete it related resources at anytime

• Go to instance page, launch a new instance from AWS base AMI, refer as i-AWS, no need to wait it, just stop it immediately

• Go to volume page, find the volume of i-AWS, detach and delete

• Go to volume page, attach vol-BYOL to i-AWS at mountpoint /dev/sda1

• Go to instance page, start i-AWS and login, you will see it is activated by AWS KMS.

• Do anything you want and use ec2config or ec2launch to sysprep and shutdown the server, create an AMI, the AMI will be AWS license managed and all customnized OS settings kept.

• Tip: if ec2launch or ec2config or SSMAgent doesn't start, please check routing to 169.254.169.xxx by route print, make sure it's correct, AWS services are heavily relay on these dynamically configured link-local addresses.

-- Larry.Song@outlook.com