When the initial cut of the Chromium OS source was released last week I decided to use the opportunity to see if it would run on my EEE PC 900 netbook (check out EEE PC 900 running Chrome OS on Youtube to see the final result). The first roadblock I hit with the build instructions was the Ubuntu requirement (I did give a little effort to getting it working on Fedora first). I don't have an Ubuntu box so I started out trying to use VirtualBox but that was going to take forever so I decided to move things to EC2 and what follows is the result. This isn't meant to be a replacement for the build docs since they are surely going to change, it is more of a cookbook to build Chromium (the browser) and Chromium OS using EC2 (EBS is used as well if you want to cache the source over time).
When I first started down the path of using EC2 I thought I would grab the source each time I wanted to build. I quickly ran into a snag however because it took forever to sync the source and download the Ubuntu repo. Once I had the initial sync of the source I decided I would copy it all to an EBS volume and keep that volume up to date. Using EBS to store the source feels better too since I assume Google expects people to be syncing changes only as opposed to pulling the entire source tree down every time they want to build.
I started out by finding this Ubuntu AMI for a base to work from. For the most efficient compile times I ended up using the High CPU (c1.medium) instance. I started with the default small instance but it was just too slow. With the high cpu instance you are looking at about 45 minutes to build the OS after you have the source synced for the first time and if you add building Chromium in there you are looking at around 55 additional minutes. All told you can have a complete build in less than 2 hours even if there are some source updates needed. For EBS you need a 3G volume for the Chrome OS source plus Ubuntu package repo and a 4G volume for the Chromium source.