How to port your OS to EC2

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2021-05-21 08:30:04

Prerequisites Before we can talk about building images, there are some things you need: Your OS needs to run on x86 hardware. 64-bit ("amd64", "x86-64") is ideal, but I've managed to run 32-bit FreeBSD on "64-bit" EC2 instances so at least in some cases that's not strictly necessary. You almost certainly want to have drivers for Xen block devices (for all of the pre-Nitro EC2 instances) or for NVMe disks (for the most recent EC2 instances). Theoretically you could make do without these since there's some ATA emulation available for bootstrapping, but if you want to do any disk I/O after the kernel finishes booting you'll want to have a disk driver. Similarly, you need support for the Xen network interface (older instances), Intel 10 GbE SR-IOV networking (some newer but pre-Nitro instances), or Amazon's "ENA" network adapters (on Nitro instances), unless you plan on having instances which don't communicate over the network. The ENA driver is probably the hardest thing to port, since as far as I know there's no way to get your hands on the hardware directly, and it's very difficult to do any debugging in EC2 without having a working network. Finally, the obvious: You need to have an AWS account, and appropriate API access keys. Building a disk image The first step to building an EC2 AMI is to build a disk image. This needs to be a "live" disk image, not an installer image; but if you have a "live USB disk" image, that's almost certainly going to be the place to start. EC2 instances boot with a virtual BIOS so a disk image which can boot from a USB stick is almost certainly going to boot — at least as far as the boot loader — in EC2.

You're going to want to make some changes to what goes into that disk image later, but for now just build a disk image. Building an AMI I wrote a simple tool for converting disk images into EC2 instances: bsdec2-image-upload. It uploads a disk image to Amazon S3; makes an API call to import that disk image into an EBS volume; creates a snapshot of that volume; then registers an EC2 AMI using that snapshot.