cd rootfs_dir
sudo su
find . | cpio -H newc -o | gzip > ../initramfs.cpio.gz
cd kernel_dir
export ARCH=riscv export
CROSS_COMPILE=riscv64-linux-gnu-
make k1_defconfig
Add rootfs image to kernel image in make menuconfig
make menuconfig
Then build kernel image
LOCALVERSION="" make -j$(nproc) Image.gz dtbs modules
cd /srv/tftp
mkimage -f in.its out.itb