OPNsense Boot Freezes on Mini PCs

OPNsense boot freezes on Mini PCs

Boot freezes on OPNsense can leave a Mini PC sitting there with no useful clue as to why. UART settings are one place to look. If serial console handling is wrong, the system can hang before it gets properly underway.

I have also seen reports of the same thing after updates or changes to system settings. One example was an MSI Cubi that installed cleanly, then started freezing on later boots. That sort of behaviour is miserable, because the first boot gives you false confidence.

UART and the boot process

UART is part of the console path during boot. On headless kit, that matters. If OPNsense is trying to use a UART device that does not play nicely with the hardware, boot can stall.

A common workaround is to disable the UART devices in /boot/loader.conf.local. That is ugly, but if the box is freezing before it finishes booting, ugly is fine.

What tends to cause it

• UART settings: misconfigured serial console settings can stop the boot process.
• Hardware mismatch: some Mini PCs simply do not behave well with OPNsense.
• BIOS settings: serial port options, legacy support, or boot mode can interfere.
• Updates: changes after an update can leave loader.conf.local in a bad state.

What to change

Disabling UART is the main fix described here. Add these lines to /boot/loader.conf.local:

hint.uart.0.disabled="1"
hint.uart.1.disabled="1"

If you are editing the file from the console or over SSH, these commands will append the lines:

echo 'hint.uart.0.disabled="1"' >> /boot/loader.conf.local
echo 'hint.uart.1.disabled="1"' >> /boot/loader.conf.local

After that, reboot and see whether the box gets through startup cleanly.

BIOS settings are worth checking too. Disable serial ports you are not using, and make sure the firmware is set to the boot mode the machine actually expects. If the same freeze keeps coming back, the hardware may just be a bad fit.

Basic checks when it still hangs

• Connect a monitor and watch the boot messages.
• Turn on more detailed boot output if you can.
• Back up the config before making changes.
• Check whether the issue appears only after an update.

If the box only boots after UART is disabled, that is useful enough on its own. It is also a reminder that small Mini PCs can be a bit fussy when you ask them to behave like proper firewall hardware.

There is a user report on Reddit describing the same kind of freeze on an MSI Cubi.