The Linux kernel requires that initrd images contain a /init file for the image to be used as an initrd, even if it is empty. Adding it into the rootfs directory creates a race, that can upset tar when building both a .tar and .cpio image file ("tar: .: file changed as we read it"). Additionally, whether or not the tar file will contain the /init file is also up to the race condition.
1 configure --with-template=feature/initramfs-integrated 2 make fs