EC2 - New Instance Vs (remount) EBS-backed instance

Question

• I have a an Ubuntu-14.04 EC2 instance running with EBS volume

• I regularly take snapshot

• I launched a new instance Ubuntu-16.04.

• I detach the root volume
• I created a EBS volume from snapshot above
• I re-attached the volume.
• I see all the data and my servers seem to work on the new instance. For eg. mongo, app servers etc.

My question is (other than app data):

• What are the differences between the new instance and the instance launched via an existing EBS?

• Is the existing-EBS-launched instance supposed to work like the old instance without any changes, out-of-the-box?

Answer 1

What are the differences between the new instance and the instance launched via an existing EBS?

Answer- first of all, understand what EBS is, in a simple language, it is a block storage volume for use with Amazon EC2 Instance. So Whenever you launch a new Instance via an existing EBS, all the stuff/ any manual changes on the disk which you have done previously will be automatically reflected in your new Instance, as you are using the same disk (Block Storage). It's just when you want any kind of modification like wants to change the key pair at that time we detach the volume, do the modifications and again attach the volume (disk).

Is the existing-EBS-launched instance supposed to work like the old instance without any changes, out-of-the-box?

Answer- yes Existing EBS launched instance work as the old instance, its just what kind of modification you have provided to the new instance. Suppose while launching you have changed the Type of instance, key pair, attach different security group. So all these changes will be reflected and all the manual operations done on Disk will remains same.