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.

Secure and Efficient PR Workflows for OpenEmbedded Layers

We've been using a pull request (PR) workflow with GitHub Actions for public OpenEmbedded layers such as meta-rauc, meta-labgrid and the LXA TAC BSP for years. This approach enhances visibility via GitHub, simplifies onboarding for new contributors, and provides automated feedback through CI, reducing maintainer workload.

Due to concerns with build-testing untrusted code, we were using GitHub's hosted runners with regular SSTATE pre-building on a separate server. This limited performance, especially for PRs changing global config variables, and made the PR workflow less smooth than it could be. To address this, we implemented a custom runner which uses QEMU on self-hosted hardware to run ephemeral VMs. SSTATE and DL_DIR can be read from the host, balancing build speed with security.

The talk will explore the trade-offs and challenges of this approach, show what we have working so far and how it can be reused by others for their layers.