Log to production host over SSH with direct ethernet cable?

[lv82]

@chrischabot

I suspect that you’re right that this might not work on production ResinOS images.

I was under the same impression after reading Remote access to Raspberry PI 3 in LAN.

@chrischabot

Security is a huge deal to us, and having an network accessible ssh port open could invite various nefarious intrusion attempts. To prevent this, we only make ssh available over the secure VPN connection.

That makes perfect sense.

@chrischabot

I’m guessing the main problem occurs when the devices network is down, otherwise I assume resin ssh would be sufficient right?

Absolutely. We’d like to be able to debug things locally and run a few commands on the host OS to understand why the device drops the cellular connection. Mostly when we add a new device to the fleet by hanging it up a postlamp, where it is not easily reachable later on.

@chrischabot

There’s a few approaches that might help to deal with a modem that’s acting up. First of all it’s worth making sure you have autoconnect set: https://docs.resin.io/reference/resinOS/network/2.x/#cellular-modem-setup

Our Ublox L210 modem is recognized as an ethernet device so we copy the following file to system-connections whenever we flash a new device:

[connection]
id=public-cellular
type=ethernet
interface-name=usb0

This being said, I am willing to test your approach with type=gsm and autoconnect=true. From what I understand, network management was vastly improved in ResinOS 2.x and the file above was created with Resin 1.x in mind.

@chrischabot

if that doesn’t work and the modem needs a reset, you could write a custom script that monitors the modem’s / network status and either reboot the entire device by calling the API on the device supervisor:
Interacting with the balena Supervisor - Balena Documentation

Great minds think alike. We already have a pending Jira ticket for this

@chrischabot

Or in the case where it’s not acceptable to have random reboots on connectivity failures, you could try to hack up a custom script that resets the modem device, there’s some inspiration here:
raspbian - How do I reset a USB device using a script? - Raspberry Pi Stack Exchange

I will certainly have a look at this too.

Thanks a lot @chrischabot. While the initial issue is not entirely solved yet, I learned a great deal reading your answer.