Good point !
I will study this also... thanks for the advice...
No, we need to...
An upgrade of OpenWrt firmware will only modify the default rootfs, so we need to synchronise, to copy all files, of this new fresh rootfs to the extroot !
@vgaetera already done some evolution of his extras scripts in this way... but for overlay...
The hotplug may be used to do this sync also, I think, it is what I want to test soon !
Yes, it is the one I mentioned upper.
I have not tested myself... yet.
If you define an overlay, as I have partially test in the topic Request for Best Practice for eMMC devices , instead of a full extroot... it may be more simple and fit our needs !