If you need to restore the original Thecus firmware for some reason, you can follow the instructions below. Please note that this will only work if your Debian system is still working. If Debian is broken but the machine itself works, it is possible to restore the original firmware from within RedBoot, either by using telnet to RedBoot or a serial console.
First of all, you need to get a copy of the N2100 firmware. If you don't
have your copy anymore, you can download it from Thecus firmware site. Once you have the
.bin file, you need to decrypt and unpack it. For this, you need to have
openssl package installed.
openssl enc -d -des -in N2100_FW_2.01.10.bin -out upgrade.tar.gz \ -K 7A9816A4C275D557 -iv 0 -nosalt -nopad tar -xzpf upgrade.tar.gz
You can ignore the warning from gzip and error from tar that the last
command will show. You will now have several files in the
directory. For us, only the files
zImage are of
interest. You need to write these files to MTD flash, which is quite
simple. First, check the file
/proc/mtd and look which MTD partition is
associated with the ramdisk and the kernel. This should be mtd1 and mtd2
respectively but please check
/proc/mtd to ensure that this is the same
on your machine. Then write the files to these partitions.
dd if=ramdisk.arm > of=/dev/mtdblock1 dd if=zImage > of=/dev/mtdblock2
When you reboot your machine, the original Thecus firmware will start. Now you should check if there's a new Thecus firmware available and if so upgrade to the latest firmware using the Thecus upgrade procedure.