Converting Instance Store Instances to EBS backed Instances

Sounds simple enough right?

Well, yes and no. There are quite a few blogs and posts about how to do this, and they all vary in their approach. Essentially, the theory goes that you start with an instance store instance, you then allocate an EBS volume and attach it to the instance (10GB), you then copy all of the contents of the root instance store volume into EBS volume, detach the volume, take a snapshot of the volume, create an ami from the volume, and voila, you then have an ami which will launch an EBS backed version of the previously instance store based instance.

This all sounds great in theory, but what are the commands actually needed to initiate the transfer of the root instance store storage over to the newly attached EBS volume? Turns out the best command to use is dd. DD initiates a full block by block copy of one drive to another. Turns out, if you attach the EBS volume via the management console, you would only need to SSH into your instance and then perform one command:

dd if=/dev/sda1 of=/dev/sdf bs=4096 conv=notrunc,noerror

And with that command, everything I said above can then be done.

The process is not quite as easy with Windows based instances as the Windows OS is not natively equipped with DD like Linux is. You can download DD for Windows and more or less follow the same process, however it takes longer to perform each function on a Windows OS compared to Linux for many various reasons


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