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I am trying to create an Amazon EC2 instance. I want to create a micro, 64-bit, Ubuntu 12.04 LTS instance.
In Amazon Web Services I have seen all instance have AMI numbers. Now I found two ami(s) with numbers ami-8a7f3ed8 and ami-b8a8e9ea. both looks same to me - micro, ebs-based, 64-bit Ubuntu 12.04LTS images.
If so, what is the difference and why two number for the same machine image?
AMIs are machine images. They are essentially snapshots that you can use to create a new instance. It is possible to have 2 snapshots that have exactly the same data.
For instance, you can create an AMI from an existing instance to get a new AMI with a new number. Each time you repeat the process for the machine, you will create another AMI with a different number. If nothing has changed on the source machine, all of these AMIs will be virtually identical.
I believe the AMI IDs don't signify anything in particular, but are specific to regions, so an otherwise identical US-WEST AMI will have a different ID from a US-EAST one, and so on.
If you're using Ubuntu, you may want to look at the official Ubuntu AMIs:
AMI ID is a combination of OS, architecture, ebs, zone and it's release. You should check if the zones/regions are also identicaly for the AMI's you listed.
