Record of Site Issues #1

Environment And Situation

Control room of an apartment
Number of installed product : 1 (PC-based NVR, dual-LAN supported)
Remote support : O

Reported Issue

When the user connects LAN cables to both NIC on the product(one NIC is connected to a private network and the other one is connected to internet)simultaneously, internet is unreachable.
Monitor connection keeps disconnected after system booted. It happens in random minutes(mostly between 1~5) - The colleague in the site told me he's not sure whether it's just about monitor disconnection or the entire system down.

Diagnosis And Assumptions

I asked to change the monitor but the monitor issue kept happening. -> The monitor was innocent.
If it was the case that the entire system was down, it might be because of kernel panic. -> I needed to check kernel messages using dmesg and journalctl
Every time the monitor issue happened, fans on the product started running faster.
I was debugging via Anydesk, but when the monitor issue happened, Anydesk remote screen stopped.
This site was where I'd already resolved other issues. But back then, there was no kind of this issue.

-> Suspicion on hardware(GPU or CPU heat problem, power supply issue, etc.)

-> Suspicion on environment(Based on the fact that the monitor issue was not there in the site back in the day) - The user might have connected other products on the same power strip

-> Suspicion on the product itself(hardware related malfunction caused by physical shock).

First Solution

-> Recall the product and check it in company.
-> After check the product in the company, send it to hardware vendor.

Second Diagnosis After Recall the Product

The monitor issue didn't appear again.
I checked the recording data -> !!Recording data was well!! == The system didn't go down entirely. It was almost surely about only VGA issue. -> The user might have connected other products on the same power strip or been about another electronic issue.

Final Conclusion

VGA malfunction caused by electronic issue(site dependent)

Solution

After all, the issue didn't happen again.

So we decided to let the product run for a day and if there's no other issue then get it back to the site and check the overall environment(with installation technicians)

About Network Issue

-> Even though I couldn't check the network issue properly, I was pretty sure that the issue was related to routing metric(similar issues happened multiple times in other sites)

Keep This in Mind

When system related issue happens, check recording data first.
Even if an electronic issue occurs, it does not necessarily affect the entire system. In this case, only VGA output appeared to be affected.