I have a t1.micro instance with /dev/sda1 volume attached. Now I am out of disk space and migrating to a larger volume. I created the larger volume from the original disk snapshot and attached it to a new instance (for test) as /dev/sda1. The instance doesn't start with error:
Invalid value 'i-cf3acXXX' for instanceId. Instance does not have a volume attached at root (/dev/xvda)
If I attach the volume as /dev/xvda, the instance doesn't start. First, it goes into "Running" state, but then the state falls back to "Stopped".