If you are using EBS root, you can also do something like the following:
- Create a SNAPSHOT of your old system's root volume. You may need to stop your instance for this process. This is usually faster than creating an image.
- Create a new volume from the SNAPSHOT in the new availability zone.
- Choose "Launch More Like This" button on the old system and launch the same AMI into the new availability-zone.
- Stop the instance once it has been created. Note it's root device which is often
- Disassociate and delete the auto-generated root EBS volume that was associated with the new instance.
- Associate the new volume you created with the new instance in the new availability zone with the root device you noted above.
- Boot the new instance and validate everything looks good.
If you are using community images then you should consider booting the image you are using and then immediately making an image from it that you own. Otherwise, you run the risk of a community image getting removed and you not being able to do the "Launch More Like This" and other operations.
I usually create a small (~8gb) image from the community image and then change the root volume to my larger (>$200gb) EBS partition.