Use telnet/ssh to mount the recovery partition /dev/mmcblk0p2 somewhere; there you will see a upgrade/ folder which contains fs.tgz (instead of KoboRoot.tgz) and subfolders for kernel/uboot images. And you combine those files with your desired firmware upgrade.
On my H2O it looks like this:
Code:
upgrade/
upgrade/db.tgz
upgrade/fs.tgz
upgrade/mx50-ntx
upgrade/mx50-ntx/u-boot_lpddr2_512-E606G0-LPDDR2.bin
upgrade/mx50-ntx/u-boot_mddr_256-E606F0B-K4X2G323PC.bin
upgrade/mx50-ntx/uImage-E606F0B
upgrade/mx50-ntx/uImage-E606G0
On a different platform there may be no mx50-ntx but other folder with similar structure, containing kernels for that platform such as you also (sometimes) find in the firmware update zips; the principle is the same.
The db.tgz has the initial database, user manuals and stuff so if you fancy you could even put a backup of your actual database in there. (not enough room for books though)
However I'll repeat it, you're more likely to brick your reader by doing so. It's simpler and safer to just do this via USB after the regular firmware reset. You can put up the firmware update you want manually, including backups of your kobo database and books.