Running illumos on AWS - the first Tribblix AMI

I've run Tribblix on all sorts of hardware - desktops, servers, even the occasional laptop. I've had success running it on some of the smaller cloud providers that allow you to install from a custom ISO, or iPXE, such as my adventures with Vultr.

However, running on AWS has eluded me. You might wonder why you would want to, but the reality is that AWS is a huge player, with many people turning to it as their default (and often only) option. So giving everyone who uses AWS access to Tribblix would be a good thing, and would also offer an easy route for people who might want to play with Tribblix to do so.

The first thing to realize is that AWS is not so much a single cloud as a set of independent clouds. Each region is independent, and has a different set of capabilities. For example, EFS is only available in a few regions. These differences can affect us.

On AWS, there are 2 different types of guest. We have pv (the older, paravirtualized) and hvm (the newer, hardware assisted). Any given AMI (Amazon Machine Image) will only run as either a pv or a hvm guest. And some EC2 instance types are pv, others hvm. Newer regions (such as London) are exclusively hvm, so pv isn't an option.

Building an AMI from scratch looked a little daunting, so I looked to see what other illumos distributions might have made AMIs available. If you go to the community AMI page when launching an instances, the only one you'll find is OmniOS. They even have a page explaining how it was done. The snag is that all their images are pv. For my first set of experiments then, I was operating in the Dublin region.

The OmniOS AMI boots up just fine and works pretty much as you would expect. No problems there. How to get Tribblix running though?

The answer lies in the beauty of ZFS and Boot Environments. The basic approach here is to take a running OmniOS image, create a new Boot Environment, install Tribblix into that Boot Environment, and make the Tribblix Boot Environment the one to boot from next time. Once I've successfully booted the Tribblix image, I can clean up and delete the original OmniOS files.

One of the advantages of Tribblix is that I have my own installer. It's quite a bit simpler than some of the other distros, and thus much easier to mangle to do things in new environments. I decided to use the iPXE image as used in my Vultr experiment, because it was easy and I had it to hand. I then wrote a modified installer script (source here) called img_install that was based on my over_install script used to drop Tribblix into an existing ZFS pool. The difference is that the old over_install was run in the context of a Tribblix Live CD; the new img_install is run in the context of an alternative distro. The other thing in that script is that I don't do any boot loader fiddling - the pv instances have a special pv-grub, which I'm careful not to touch.

(By the way, the same trick will work for other illumos distributions. You just need a source archive of some sort and a script to unpack it. For example, I have a script to unpack some of the ISO images in the tribblix-zones repo, which I use to create alien-root zones. It's the same idea of installing an image in a alternate path.)

So all that was involved was to:

• Start up an OmniOS instance (a micro instance on the free tier works fine)
• Run the img_install script to create the alternate BE
• Reboot, so you boot into Tribblix
• Delete the old OmniOS BE
• Finish off the install and apply updates

Then you can do the normal create an image trick on the AWS console, and you have a nice shiny Tribblix AMI.

That all worked out just beautifully. Tribblix runs on EC2 just fine.

In the next article, I'll describe how to create a hvm AMI.