Why can't I modify the sysfs

Hi

I was going through a tutorial on a DE10-Nano on how to make custom overlays, and I seem to have hit a bit of a puzzle.

https://rocketboards.org/foswiki/Documentation/HOWTOCreateADeviceTree

At one stage, it requires me to create a directory and update values in sysfs.

sudo mkdir /sys/kernel/config/device-tree/overlays/my-cv-fpga-overlay 
sudo echo my_cv_fpga_overlay.dtb > /sys/kernel/config/device-tree/overlays/my-cv-fpga-overlay/path 

Problem is I cannot seem to do so. the command returns "Operation not permitted" error message.

I tried the LDXE linux image from terasic and also a rootfs/kernel that I made based on ubuntu base and kernel 4.9...lsti

https://github.com/rsarwar87/altera-soc-rootfs

Presumably it is some kernel configuration that I need to turn on maybe to allow modification of sysfs? I was wondering if anyone could kindly shed some light on this puzzle.

Thanks

RD