Netboot without throwing a FIT

For years, Ahmad’s ideal has been simple: unpack a rootfs on a server, mount it over NFS (or usb9pfs), boot directly into it, and everything just works™.

But as secure boot becomes the default on many embedded systems, squeezing in a network-booted kernel is getting harder and often falls outside the supported boot flow entirely.

Fortunately, some recent improvements in the kernel build system pave the way for a far less invasive netboot setup. This talk gives a quick tour of the key pieces:

• The image.fit target for arm64 introduced in v6.10
• The modules-cpio-pkg target introduced in v6.19
• Initramfs that bind mounts its modules over the rootfs
• Optional concatenation of multiple initramfs in the bootloader

In ten minutes, you’ll see how these changes raise the netboot FITness of Linux, so you can keep printk-debugging to your heart’s content.