CTRL-ALT-DEL sometimes gets passed to the Pi instead of the host system

[mabalmer]

I've noticed this behavior specifically when trying to do installations of Win98 via Win98 Quick Install, which uses a Linux kernel as part of its initial bootstrap process. Once the kernel has booted and the menu system for installing the operating system has loaded, CTRL-ALT-DEL is intercepted by the Pi and causes the USB4VC to reboot itself, rather than the host computer.

Details of the system in question:

• Motherboard: MSI MS-4144
  • CPU: AMD 5x86-DX5-133, overclocked to 160MHz
  • Chipset: SiS 85C496/497
  • Keyboard BIOS: AMIKey-2 (presumably a standard 8242/8342 variant)
• Devices:
  • VGA: DataExpert ExpertColor DSV3325DX (S3 ViRGE DX, 4MB)
  • Network: 3Com 3C509B
  • Sound: Pro AudioSpectrum 16
  • IDE0: Dual 8GB compact flash cards
  • IDE1: ZuluIDE attached as primary, no secondary

Keyboard attached to the USB4VC is a Logitech K800 via wireless Unifying adapter.
Mouse attached is a Logitech Triathlon M720 paired to the same Unifying adapter.
Joystick attached is an 8BitDo SF30 Pro Wireless controller, attached via USB cable.

Let me know if additional configuration details are needed.

[dekuNukem]

Hi there! I thought I disabled the three finger salute in the OS image, not sure how it regressed on yours.

Anyway, feel free to ssh into it and try this:

sudo rm /lib/systemd/system/ctrl-alt-del.target
sudo ln -s /dev/null /lib/systemd/system/ctrl-alt-del.target
sudo systemctl daemon-reload

Source: https://librpip.frasersdev.net/linux/raspbian/

[mabalmer]

I think I understand a little more about what's going on here -- I've noticed that sometimes, the USB4VC reboots itself with CTRL-ALT-DEL when the host system is frozen or busy to the point where keyboard inputs are lagging.

The first press of it passes through to the host as expected, and then if the USB4VC receives more of them in succession, it might pass a few more to the system but it will eventually stop and the USB4VC will stop accepting inputs because it's rebooting itself (the little white light that shows that it's processing inputs stops blinking entirely and the green activity light on the side of the Pi starts flashing furiously like it's in the middle of a startup routine).

Not sure what's actually happening here, but if you have more ideas to try to get to the bottom of it, let me know.

[megatog615]

Perhaps it's SystemD's ctrl-alt-del burst action? By default it is configured in /etc/systemd/system.conf to force reboot the system. If you uncomment CtrlAltDelBurstAction and change it to none it disables this.