How to network boot Pi over WiFi

Question

Since the Raspberry Pi 3B it has been possible to take out the SD card and boot over the network however this seems to imply wired Ethernet only.

Is it possible to somehow specify a WiFi network, password, etc. so that you can also do a network boot over a wireless network as well?

It appears to be possible to patch the boot ROM to hard code certain parameters (like the TFTP server address) so it would seem that flashing WiFi network details into the boot ROM is doable, but I'm not sure whether the boot ROM has support for the WiFi interface.

Answer 1

I ended up doing this in a roundabout fashion. I found an old WiFi router on eBay that cost basically nothing as it was obsolete, and set that up as a client on my wireless network. That gave me four wired Ethernet ports on the router I could plug the Pi into, which would have their traffic forwarded over the wireless network.

This meant the Pi thought it was on a wired network and it booted over that "wired" connection normally, when in fact thanks to the WiFi router it was actually connected via WiFi.

As a bonus it meant I was able to network boot older Pi devices over WiFi even though they don't have onboard WiFi, by just adding the usual SD card with bootcode.bin on it to enable normal network booting.

I used this method to successfully network boot a Raspberry Pi 1B+, 3B and 3B+ over a wireless network.

If you get a router with a USB port on it that can deliver enough current, then it also means you don't need a separate power supply for the Pi, you can just plug the router into power and then run the Pi off its USB port.

Answer 2

No WiFi boot is not supported and most likely will never be either. It's way to complex to fit inside a bootloader.

• Malvineous: What about on an SD card?
• Ronny Nilsson: I don't understand what you mean with a SD card. If you have an SD card you boot from that yes(?).
• Malvineous: Sorry I meant could you put an updated bootloader on the SD card, so the Pi "boots" from the SD but that code just does a PXE boot over WiFi? When you said a WiFi boot is too complex to fit inside a bootloader, having it on the SD card should remove any sort of size restriction. In my case I want to boot over the network to simplify upgrading multiple Pi devices (just upgrade the shared network filesystem and reboot them all), so I don't mind if it has an SD card, I just want it to load the kernel and root filesystem over the network.
• Ronny Nilsson: @Malvineous There is no ready made solution for your case to my knowledge. I think what you can do however is to let your devices do "self upgrade". Once they have booted normally; have a program query your server for the latest version, download and upgrade itself and reboot.