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Comment by newhouseb | Hacker News Reader

This is awesome - what would be the remaining use case/advantage for using an AMI when you can now snapshot to more widely supported formats and import them?

Edit: Oh, this is windows only, significantly less exciting. I wonder why linux isn't supported?

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I wonder why linux isn't supported?

Linux runs on EC2 via Xen/PV, which is a kernel-hypervisor interface not provided by other (non-Xen) virtualization systems. Exporting linux AMIs would require reaching inside your filesystem and modifying your kernel, which is far outside of the scope of anything Amazon would want to do (both in terms of "really complicated" and "liable to accidentally break things"). The same applies to importing images, of course.

[I don't work for Amazon and I don't speak for Amazon. The above is speculation based on information published by Amazon about EC2.]

Kernel isn't a big deal, Colin. An entire filesystem should boot the same when exported. If you rsync / elsewhere, twiddle a few knobs like network config then reboot, you should be able to move an Amazon image anywhere. I have successfully done this between disparate virtualization providers, and Xen to dedicated.

Amazon is unique in that they use PV-Grub everywhere to boot a customer filesystem kernel (newer behavior), whereas on other virtualization providers like Linode, the kernel is selected at domain creation time by the hypervisor, and loaded from the hypervisor's filesystem (not the customer). You can use PV-Grub but it's opt-in, not opt-out.

I have successfully done this between disparate virtualization providers, and Xen to dedicated.

I'm betting you were running Xen/HVM then. (Most people do, these days.)

Well, yeah, but it's the filesystem, not the virtualization tech. You could rsync a dedicated to a dedicated and it'd be fine.

It's not really complicated. If you have, say, a RHEL 6.2 image booting on EC2 you can take the same root filesystem and boot it with a kernel from any other RHEL 6.2 installation with some editing of the grub configuration.

But you're right that Amazon isn't really interested in doing that work for you. Linux people who really need this are no doubt already doing it.

Sure, but if you're running a custom kernel you'd need to run a custom non-PV kernel. And there's no remotely sane way for Amazon to figure out what customizations people have made to their kernels.

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