If you’re attempting to install updates or make config changes, it helps to have a backup of your environment. In AWS, it’s easy to make EBS snapshots, but if you make a snapshot of your root device, it’s not obvious how to restore it.
- Create a new volume from the snapshot you’d like to return to.
- Detach the Root device EBS volume from your instance.
- Attach the new volume under the following device: /dev/sda1
If you try to boot without a root device, AWS will give an error about /dev/sda1 missing, but oddly when you add a block device, you enter them in the xvd[a-z] format, and leave off the /dev/.