Yesterday I had to repair a wildly blinking QNAP NAS TS-212 that could not be accessed via HTTP Web UI or SSH. Also the system rebooted regularly and it was not clear why … Also googling didn’t get me anywhere, except wild speculations in all possible directions. Hmm… in a case like this, you wish you had the good old serial console, which gives you more insight into the system.
The precautionary note: Everyone tinkers at their own risk! You should also have some previous knowledge to be able to carry out the steps described here successfully! So, don’t whine if you cause a short circuit or something like that and you have ruined your QNAP! 🙂
After unscrewing the case the positive surprise: On the mainboard you can actually find a 4-port connector, which according to the information in the net actually points to a RS-232 interface. On my model TS-212 the connector is labeled CN9. It is a 3.3V TTL connector and the four pins are TX, VCC, RX, GND.
Now the only question is, how can I tap the serial port and use it on my laptop via serial-USB adapter? The solution: An Arduino Uno board brings everything I need! On one side we have a digital input strip with connectors for RX, TX and GND and on the other side we have the USB connector to connect it directly to the laptop. With a small adapter cable the connection works easily (see picture).
Then I start the program Minicom on my Linux laptop with the Arduino port /dev/ttyACM0 and with the terminal settings VT102, 115200 Baud, 8N1. And lo and behold, immediately I have the entire output of the QNAP boot process in my terminal.
This now offers me much better possibilities for error analysis. Furthermore, I can also intervene in the boot loop by pressing any key shortly after the reboot when “Marvell UBoot” is displayed. There are some system commands available here that might help.