HOWTO operate the console of the APU via the network (using ser2net)

[thowe]

The PC Engines APU devices are a cost-effective, stable and reliable hardware for a firewall based on OPNsense. Accordingly, I have two of them in use.

The APUs are so-called headless systems. I.e. they have no monitor output but are initially connected via the serial port. This works fine and once OPNsense is up and running, console access is usually no longer necessary, since OPNsense can be managed completely via the web UI (and occasionally ssh for very special needs).

In very rare cases, however, it is necessary to access the console, e.g. to change the BIOS settings or if a manual intervention is necessary after an unsuccessful update (but I have never had to do this).

Of course, in such a rare case you can go with the notebook close to the firewall and temporarily access the console with a Serial2USB cable. I have done this in the past maybe once a year at most and otherwise tried to prevent it, also because it was a bit tedious.

Recently I saw on the web that you can easily create a telnet access to a serial port with the tool ser2net. Usually you can find instructions for a Raspberry Pi. But this works for all such single board computers. I had an old Orange Pi PC lying around, which I converted to my Serial2Network device:

• install armbian
• install ser2net as an autostarting service
• configure ser2net
• access it with telnet [IP] [portnumber

The Orange Pi PC is now sitting in our tech basement on top of the APU. It takes power from the USB port on the APU. And the Serial2USB cable from PC Engines connects the console of the APU to the USB port of the Orange Pi PC.

Here I came across the possibility and it is described: https://www.jpaul.me/2019/01/how-to-build-a-raspberry-pi-serial-console-server-with-ser2net/