Network Nirvana: PXE Boot with OPNsense, netboot.xyz, and Unraid

We’ve all been there – tinkering with our devices, pushing boundaries, and sometimes, well, messing things up. That’s exactly what happened to me with my old notebook. In a moment of misguided experimentation, I managed to botch the BIOS settings so badly that booting from USB became impossible. Talk about a facepalm moment! But as they say, necessity is the mother of invention. With USB booting off the table, I found myself exploring an alternative I’d heard about but never used: PXE booting. Little did I know, this mishap would lead me down a fascinating path of network-based boot solutions.

What is PXE? A Technical Introduction PXE, which stands for Preboot Execution Environment, is a powerful protocol that allows a computer to boot from a network interface independently of available data storage devices or installed operating systems. Developed by Intel, PXE is part of the Wired for Management (WfM) specification and has become a standard feature in modern network cards and BIOS/UEFI implementations.

How PXE Works: The Technical Breakdown

Network Interface Initialization: When a PXE-capable device boots, it initializes the network interface card (NIC) before any other boot devices.
DHCP Discovery: The client broadcasts a DHCP discover message with a PXE-specific option to locate a PXE boot server.
DHCP Offer: A DHCP server responds with an IP address offer and the location of boot files.
TFTP Transfer: The client uses TFTP (Trivial File Transfer Protocol) to download a small network bootstrap program (NBP) from the specified server.
NBP Execution: This bootstrap program is executed, which typically loads additional files or a lightweight OS kernel.
Boot Process: The downloaded OS or boot image then takes control of the boot process.

PXE leverages several protocols to achieve this network boot capability:

DHCP (Dynamic Host Configuration Protocol) for IP configuration and boot server discovery
TFTP (Trivial File Transfer Protocol) for transferring boot files
UDP (User Datagram Protocol) for network communication
IP (Internet Protocol) for routing

One of the key advantages of PXE is its ability to work with a bare-metal system, requiring no pre-existing OS or bootloader. This makes it invaluable for scenarios like mine, where traditional boot methods are unavailable, as well as for large-scale deployments, system recovery, and diskless workstations. As I delved deeper into setting up my PXE boot environment, I realized that this mishap had opened up a whole new world of possibilities. Stay tuned for my next post, where I’ll walk you through the step-by-step process of setting up a PXE boot server and bringing my old notebook back to life!