Help for thread [6039y] **GUIDE** Repartitioning of the internal memory

Hi, sorry for my bad english,

I've trouble to understand what's wrong or I miss : want to run the 1st command umount /cache at the 4th step (unmount all partitions of the internal memory )

C:\Program Files (x86)\Minimal ADB and Fastboot>adb shell
shell@idol347:/ $ umount /cache
umount /cache
failed: Operation not permitted
1|shell@idol347:/ $

Actually the phone are root, TWRP v2.8.6.0 by decker. I've also swap with twrp-2.8.7.0-idol3-6039y-with-gdisk instead of just run it one time : same trouble, Operation not permitted

Any idea ?



Just to be sure, when it writing go to device, we are under the TWRP -> Reboot -> System ... and we go to android ? And at this point I run adb shell, that ok ?
I would also say, that my first smartphone / 1st root / 1st trying :o