We have talked about u-boot, linux kernel. In this post, we will move on to build the root file system. We will start from initramfs provided by linux-sunxi.

The initramfs provided by linux-sunxi is provided for system upgrade purpose. We will need to make changes.

Navigate to the root directory of the kernel:

Create a new directory rootfs:

#mkdir  rootfs

Copy initramfs from pcDuino3 to rootfs:

#cp ~/a20-kernel/linux-sunxi/rootfs/sun7i_rootfs.cpio.xz  rootfs

Unzip rootfs:

#xz  -d  sun7i_rootfs.cpio.xz

Unzip cpio:

#cpio -idmv < sun7i_rootfs.cpio

Modify init to remove the upgrade process:

#vim rootfs/init

Delete ‘update.sh’:

#rm rootfs/update.sh

Configure the kernel to make the kernel support initramfs:

#ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- LOADADDR=0×40008000 make menuconfig O=build -j 8

General setup —>

[*] Initial RAM filesystem and RAM disk (initramfs/initrd) support

(../../linux-sunxi/rootfs) Initramfs source file(s)

After done with the configuration, we need to rebuild the kernel:

#ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf-  LOADADDR=0×40008000 make uImage dtbs O=build -j 8

Follow the previous post to copy generated uImage and dtb onto the SD card, and reboot pcDuino3 with the newly copied SD: