Does U-Boot or the installed system break during upgrade?

[Cyberman tM]

Let me clarify: when you upgrade the firmware using an SD card and pressing the return/enter buttons, the existing system will not respond anymore.

Normally that doesn't matter as it's soon replaced by the new system.

Recently I tried to prevent that by removing the call to "sd_upgrade_fs.sh", which is normally found inside /etc/init.d/rcS .

The system at first behaved like expected, displaying the pictures I told it to show and even turned itself off.

When I removed the disk and started it again, pressing no buttons - it simply stopped after displaying 3 black squares (instead of 5 or 6).

I connected it to the PC, to find out if maybe merely EBRMAIN is broken, but it wasn't recognized either, so I guess the kernel has not yet loaded.

Which then leaves me to assume that the black squares are from U-Boot and it is this part that is left hanging.

But why?

Curious trivia: pressing the MENU key during bootup causes the system to show all black squares. Doesn't do anything more, though.
I tried to find answers in a U-Boot source code, but either the source was different (not likely) or I simply didn't know where to look (very likely - I'm simply not used to programs this huge and complex).


I guess I'm (again) merely discovering the obvious, hence this thread. Anyone care to enlighten me?

BTW, my experiments are done with the Cool-Er firmware, but this part seems to be Netronix standard, Kobo uses it too, and I guess all Netronix devices do.



P.S: after allowing the update to complete, everything works just fine again.