WARNING!!!Do not try this unless you know what you are doing. Clearly this could damage your equipment beyond repair. Proceed at your own risk!
I purchased a used Thecus N2100 on ebay, that had been altered to run OpenBSD. I BELIEVE the previous owner used this guide to perform the installation. My intent was to install Debian linux overtop of the OpenBSD. Unfortunately, installing the OpenBSD bootloader required deleting userland tools from the flash due to space concerns. This removes the ability to re-install the original factory firmware, and in turn, prevents the installation of Debian. Using these steps, I was able to restore the unit to original factory condition. After this, installing Debian worked as expected.
1 Parts List
Still reading? Anyway, I really didn't use any tools for this project. The only required object is the Thecus N2100, and a second PC of some sort. If you wish to open up the chassis to swap hard drives, etc, a #2 Philips screwdriver will work fine. To perform this recovery, I actually had a second working Thecus available, and was able to use its flash to recover the broken unit. I can provide memory dumps if this data if needed.
The box booted just fine into OpenBSD, but I can see how the following would help a box that can't even do that. Most of the Thecus boxes that have been updated to a fairly recent flash will have Redboot, a bootloader/utility that provides basic functionality to booting and recovering the box. See this guide for more details about accessing Redboot.
To access Redboot requires telnetting to port 9000 during the device's boot process. The easiest way to do this is with the following:
arping -f 192.168.1.100 && telnet 192.168.1.100 9000 WARNING: interface is ignored: Operation not permitted ARPING 192.168.1.100 from 192.168.1.104 eth0 Unicast reply from 192.168.1.100 [00:14:FD:10:33:8E] 6.473ms Sent 9 probes (9 broadcast(s)) Received 1 response(s) Trying 192.168.1.100... Connected to 192.168.1.100. Escape character is '^]'. == Executing boot script in 2.650 seconds - enter ^C to abort ^C RedBoot> RedBoot>
On my working Thecus, the following command showed the contents of the flash disk:
RedBoot> fis list Name FLASH addr Mem addr Length Entry point RedBoot 0xF0000000 0xF0000000 0x00040000 0x00000000 RedBoot config 0xF0FC0000 0xF0FC0000 0x00001000 0x00000000 FIS directory 0xF0FE0000 0xF0FE0000 0x00020000 0x00000000 ramdisk 0xF0040000 0x00800000 0x00D00000 0x00800000 kernel 0xF0D40000 0x00200000 0x00160000 0x00200000 user 0xF0EA0000 0x00120000 0x00120000 0x00800000Notice the 'user' directory. This is where the userland Linux tools are stored for the default Thecus firmware. On the broken Thecus, I saw this in flash:
RedBoot> fis list Name FLASH addr Mem addr Length Entry point RedBoot 0xF0000000 0xF0000000 0x00040000 0x00000000 RedBoot config 0xF0FC0000 0xF0FC0000 0x00001000 0x00000000 FIS directory 0xF0FE0000 0xF0FE0000 0x00020000 0x00000000 ramdisk 0xF0040000 0x00800000 0x00D00000 0x00800000 kernel 0xF0D40000 0x00200000 0x00160000 0x00200000 boot 0xF0EA0000 0x00100000 0x00020000 0x00100000The 'user' directory had been replaced by a 'boot' image of a different length. When I tried to manually load and boot the kernel and ramdisk, they appeared to get started, but once the kernel booted, the lack of userland tools meant no web interface, no network settings, basically a dead system. How do we get this back?
3 Exporting Userland
The working Thecus already had Debian installed on it, and provided all of the tools needed to extract the original Thecus firmware for the transplant. Looking at the forums, I determined that the flash was accessable under /dev/mtd*. To view which partitions housed the various flash images, simply view /proc/mtd. Observe:
debian:~# cat /proc/mtd dev: size erasesize name mtd0: 00040000 00020000 "RedBoot" mtd1: 00d00000 00020000 "ramdisk" mtd2: 00160000 00020000 "kernel" mtd3: 00120000 00020000 "user" mtd4: 00001000 00020000 "RedBoot config" mtd5: 00020000 00020000 "FIS directory"This looked familiar. I was able to mount these with mount -t jffs /dev/mtd3 /mnt/temp or something similar, but I wanted to extract the filesystem in its entirety. After playing with dd, cat, and /dev/mtd3 and /dev/mtdblock3, I found that a simple
cat /dev/mtdblock3 > userappeared to do the trick. I now had a file called 'user' which had the contents of mtd3.
4 Importing Userland to Flash
Importing the user image to flash proved to involve a bit of trial and error, and having made a few typos while I figured out which flags on the fis command did what, I was lucky to not blow away any other images ;) From Redboot, I ran the following to erase the 'boot' image:
fis erase -f 0xF0EA0000 -l 0x00020000Now load the 'user' image via tftp from the server 192.168.1.5 to the correct memory location:
ip -h 192.168.1.5 load -r user -b 0x00120000Now the moment of truth, flashing the image from RAM to the onboard flash chip. No mistakes!
fis create -b 0x00120000 -l 0x00120000 -f 0xF0EA0000 -e 0x00800000 -r 0x00120000 userVerify with fis list:
RedBoot> fis list Name FLASH addr Mem addr Length Entry point RedBoot 0xF0000000 0xF0000000 0x00040000 0x00000000 RedBoot config 0xF0FC0000 0xF0FC0000 0x00001000 0x00000000 FIS directory 0xF0FE0000 0xF0FE0000 0x00020000 0x00000000 ramdisk 0xF0040000 0x00800000 0x00D00000 0x00800000 kernel 0xF0D40000 0x00200000 0x00160000 0x00200000 user 0xF0EA0000 0x00120000 0x00120000 0x00800000
RedBoot actually boots the system, so we have to set it to load the kernel and initrd into RAM, then run the userland tools that set the device IP and console access. Recreate the original boot script using fconfig in RedBoot:
RedBoot> fconfig ...contents of the script below... thecus_setip fis load ramdisk fis load kernel exec -c "console=ttyS0,115200 root=/dev/ram0 initrd=0xa0800000,42M mem=128M@0xa0000000"Set any IP or other settings that you like. Reset with 'reset'. At this point, the unit booted into the original Thecus firmware! I upgraded to the Thecus firmware to 2.10, the latest version, then followed the Debian installation guide. The unit installed with no issues, and OpenBSD was gone forever. Eureka!
6 Further Info
Below is a list of most of the articles I used to piece together this procedure. Thanks to the original authors, as without the background information, I would have never recovered this piece of hardware.
http://www.cyrius.com/debian/iop/n2100/ http://www.cyrius.com/debian/iop/n2100/telnet.html http://www.cyrius.com/debian/iop/n2100/deinstall.html http://foonas.org/index.php?title=Foonas-iscsi:Install-n2100 http://david.thg.se/n2100/ http://foonas.org/index.php/Platforms:n2100-notes http://naswebsite.com/wiki/N2100_Recovering_from_a_bad_config_change ftp://ftp.openbsd.org/pub/OpenBSD/5.1/armish/INSTALL.armishThat about wraps it up. This is a fairly straightforward hack that will allow you to run Debian in all of its glory on hardware that has a limited distro on it. If you have any thoughts/additions, email them to sclebo05 AAATTT gmail.com. Thanks for stopping by!