The BananaHackers forum has all the tools needed to make backup copies to analyze and repair your KaiOS device.
You require a recovery partition that can read and flash updates in the form of a .zip package, using the SD card to use them. For example if you have a Nokia 8110 4G and the firmware is at least version 13 you have to replace the Recovery Mode with an useful one with test-keys:
To create a backup image of the partition on the sd card, simply run from root shell:
dd if=/dev/block/bootdevice/by-name/PARTITION of=/sdcard/PARTITION.img bs=2048
Where PARTITION is the name of the partition whe want to save. For example, if we want do a backup of system is sufficient to do:
dd if=/dev/block/bootdevice/by-name/system of=/sdcard/system.img bs=2048
For the data partition it changes to:
dd if=/dev/block/bootdevice/by-name/userdata of=/sdcard/userdata.img bs=2048
for the recovery is:
dd if=/dev/block/bootdevice/by-name/recovery of=/sdcard/recovery.img bs=2048
for the firmware (boot) is:
dd if=/dev/block/bootdevice/by-name/boot of=/sdcard/boot.img bs=2048
and so on. This is safe and you can do this from the normal boot.
Warning! Replacing a partition instead is very risky! Remember a very important rule:
In case you want to replace "recovery" do it from normal startup / in case you want to replace "system" do it in Recovery Mode.
Every other partition flashing is indifferent, but the important thing is to have the possibility to access at least one working mode, from where we can perform operations with root privileges.
Always place the image file to be flashed inside the sd card (in the following examples it will be always in the main folder), which is in .img or .bin format.
A classic example is the replacement of the recovery, to flash the new recovery (for example recovery.img), from the normal mode run the command:
dd if=/sdcard/recovery.img of=/dev/block/bootdevice/by-name/recovery
To flash a system partition with a system.img file, from Recovey Mode run the command:
dd if=/sdcard/system.img of=/dev/block/bootdevice/by-name/system
To flash a data partition userdata.img wherever you want:
dd if=/sdcard/userdata.img of=/dev/block/bootdevice/by-name/userdata
for a modem partition it will be:
dd if=/sdcard/modem.img of=/dev/block/bootdevice/by-name/modem
and so on.