serial console not working when no monitor plugged in

[Panther5314]

Hi guys,

bit of a strange one.. bought one of those little topton n100 router PCs which has a console port on it. While i still had a screen attached via HDMI, configured serial redirection so i could see the BIOS boot process: all good. Can see opnsense booting up: all good. At the end of the boot process, can see the opnsense login prompt: all good!

disconnect the hdmi cable and keyboard, reboot and while i can see the bios and most of the boot process - it doesn't leave me with the login prompt. The last thing it shows is something to do with the intel core temp module.

The host is booted, can connect via the network but can't do anything via serial.

• Doesn't matter what i set the administration settings to. ie Primary: serial, Secondary: none. Primary: serial, Secondary, VGA... vice verca - nothing helps
• With the screen disconnected, the opnsense boot screen shows "Serial Console" as expected. I've also tried changing that to Primary: serial, Secondary: vga. Vice verca etc. Doesn't make a difference.
• When triggering a shutdown, i see the shutdown process via serial though.

However, plugging in the HDMI cable and booting again shows the login screen as expected via serial but on the hdmi monitor, i see what i had been seeing via serial when the monitor was not attached.

Any chance there's something simple I'm missing here? Feel like im going in circles.

Cheers

[franco]

Some devices don't boot unless HDMI is connected. There are cheap HDMI dongles sold that trick the hardware into thinking a monitor is attached so you can use it in a headless fashion (although "headless" is a bit misleading when having the serial connected but the same problem still applies).


Cheers,
Franco

[dinguz]

On a related note: I have a similar device, which has the annoying habit of disabling the HDMI output if no screen is connected at boot. So in case of an issue, you can't connect a monitor later on to see what the device is doing, or work locally.

[Panther5314]

Some devices don't boot unless HDMI is connected

but it definitely does boot without hdmi connected

has the annoying habit of disabling the HDMI output if no screen is connected at boot

exactly why im trying to get the serial console working properly.

seems crazy that it only shows the login prompt via serial when the VGA is connected.

edit: i might just grab one of those hdmi dummy connectors from amazon for $9

[dinguz]

I was browsing the BIOS the other day, and when I noticed there is 'console redirection' section in there, I thought of this thread. Have you tried different settings there?

[doktornotor]

while i can see the bios and most of the boot process - it doesn't leave me with the login prompt.

That matches the behaviour observed here when using COM port and you have USB-based serial console checked in the GUI. Uncheck it.

[bman]

Take a new serial cable.
I had before similar issues, nothing I have tried worked. Just got new cable and all works flawlessly.