Before doing any of the below instructions, back up your Nook!
To replace boot files on the Nook Simple Touch (for example, uImage):
Over ADB method
Using the ADB command line:
su # mount -o rw,remount rootfs / # mkdir /boot # mount -t vfat /dev/block/mmcblk0p1 /boot # exit adb push [directory where uImage is located]\uImage /boot adb reboot
From the Nook method
Using a terminal app:
su mount -o rw,remount rootfs / mkdir /boot mount -t vfat /dev/block/mmcblk0p1 /boot
Then, using a file explorer app, copy and past uImage into /boot. If asked if you are sure you want to overwrite, say "Yes". After doing that, reboot your Nook.