Ok, so I'm in the process of creating at least 1 extra copy of whatever version of OpenWrt I'm running, so that if an upgrade fails, I have a 2nd exact copy SD.
What I've done thus far is use dd from within Debian Desktop in VirtualBox to do image copy. I've then copied Orig Image to a WIP image, so that I can revert if I mess this up. Part of what I'm doing is reducing the "rootfs" partition size. Orig I enlarged "rootfs" to fill the 64 Gb SD. But 64 G images are a pain & there's no reason for OpenWrt partitions to be that large. So 64G -> 2Gb.
I've resized using GParted inside Debian. & "truncate" utility (which I messed up first time). So I've resized the "Rootfs" partition & resized the image via "truncate", & have been able to mount the image via loop-back device. So the partitions are visible in Debian.
Now, first time I wrote the smaller OpenWrt back to SD, I used dd again, but that messed the entire partition structure & Superblock etc.
I seem to remember using Rufus in Win to write the OpenWrt image when I first started off. However looking at Rufus again, I notice that all the format options are DOS/FAT/MBR etc. OpenWrt is supposed to be an EXT4 filesystem, correct? So how have I got here, or does the OpenWrt image contain the EXT4 filesystem, & will overwrite what the Rufus writer creates?
Rufus screen --
