Yocto Linux install issue on UpBoard, reboot not found?

I successfully built upboard-image-base. The installation procedure (via UEFI - grub install menu) goes well until the very end, when it needs to reboot. The installation procedure errors out complaining that it cannot find reboot command.
I inspected the generated initrd image and actually there is no reboot under sbin.
I am using the "sumo" branch of meta-upboard, building upboard-image-base.

What am I doing wrong? Let me know if you need additional infos!