PXE Boot From S3 Without a Traditional Boot Server
How PXE netboot actually works, and how to build a minimal S3-based PXE server for Alpine Linux with UEFI HTTP boot. No TFTP server required.
The PXE boot process allows a machine to boot without any pre-existing operating system, eliminating the need for a traditional boot server. To achieve PXE boot from an Amazon S3 bucket, a few steps are required.
First, the necessary files must be hosted in an S3 bucket. These include the Alpine Linux kernel, initramfs, and modloop files. The S3 bucket's REST endpoint serves the files over HTTP, which can then be accessed by the PXE client.
Next, an iPXE binary is compiled to act as the intermediate stage for the PXE boot process. This binary is responsible for bootstrapping the client into the S3 environment.
Finally, the DHCP server must be configured to provide the PXE client with the necessary information to access the files in the S3 bucket. The DHCP client sends an HTTP boot request, which the DHCP server must respond to correctly. This response includes an option (option 60) that identifies the client as an HTTPClient, which expects the server to echo "HTTPClient" back in the reply. If the DHCP server does not respond correctly, the PXE client will silently ignore the offer without retries.
Once the DHCP server is configured, the PXE boot process can be initiated. The machine will send a DHCP request to the DHCP server, which will then respond with the correct URL to access the files in the S3 bucket. The iPXE binary will then fetch the kernel, initramfs, and modloop files from the S3 bucket and boot the machine.
Written by urgent.news from HackerNoon's reporting — not their text. Machine-written — may contain errors; check the original before relying on it.
