usb9pfs: network booting without the network

Linux v6.12 adds usb9pfs as a new USB gadget function, which can be used to mount a filesystem provided over USB.

Booting from an external rootfs in the form of NFS is already a staple in embedded systems development, but multiple issues complicate its usage:

• network interface required , which may not always be available
• Interference with normal network setup, especially in existence of switches
• Requires setup of multiple services: DHCP, TFTP, NFS...

By using usb9pfs for the rootfs, these limitations can be avoided on all devices that feature a USB gadget port.

This talk will discuss the design of 9p and usb9pfs and showcase how streamlined development on a Yocto root file system can be with both barebox and Linux making use of usb9pfs.