Modify contents of rootfs.cpio.gz.u-boot

[bfung_2]

I can successfully boot with qemu with initrd with the rootfs.cpio.gz.u-boot image creating with petalinux-build.

I'm trying to modify the rootfs contained within this image as a fun exercise. Here's what I've tried:

1. unwrapping the u-boot header

2. un-compressing

3. stdout the contents with cpio

After I make a change to the file system, I reverse the aforementioned steps. Booting with qemu is unsuccessful (I get warning messages similar to this:

vivado_plinux_test auth.err getty[242]: can't open '/dev/tty1': No such file or directory

Would someone be able to provide example commands to achieve what I'm trying to do. I'm thinking I'm missing something simple somewhere... 

[pointerdk]

It is possible to use yocto to add the files to the rootfs during the build process. 
You just have to emulate that it is an app that you install, and then only use the bitbake recipe to add the files with building anything.