Prevent the Proxmox Terminal UI installer to switch to graphics mode

I wanted to try Proxmox VE on one of the BMAX B6 mini PCs we recently bought – the ones which turned out to not meet the Windows 11 minimum requirements – and ran into an unexpected problem: Regardless whether I selected the graphical or Terminal UI installer, after a few seconds the display went black and the monitor went to sleep. Somehow the installation process switched the graphics card into a mode my monitor didn’t like. Knowing that Proxmox is based on Debian, I googled and found this post on StackExchange, which suggested a solution that worked for me:

  1. On the grub menu, select "Install Proxmox VE (Terminal UI)" (but do not press Enter!)
  2. Press E to edit the entry
  3. Add the parameter "nomodeset" to the the linux command line (without the quotes)
  4. Press F10 to boot

This worked: The Proxmox installer started in text mode, I could enter the necessary parameters and start the installation. Unfortunately when the computer rebooted after the installation, the same problem occurred again. The screen was blank and the monitor went to sleep.

So, I used the same procedure again when booting into Proxmox and this time got a console that I could actually see.

But this is only a temporary measure for this one boot process. So there is some additional change required, the one that is explained in the post linked above:

  1. Edit /etc/default/grub with any text editor (vi is installed, as is nano)
  2. Change the line GRUB_CMDLINE_LINUX_DEFAULT like this:
    GRUB_CMDLINE_LINUX_DEFAULT="vga=normal nomodeset"
  3. Save your changes
  4. Run update-grub
  5. Optionally reboot the system to test the change

So, installation worked. But I get lots of error messages on the console now, saying "PCEe Bus Error: severity=Correctable, type ==Physical Layer, (Receiver ID)". That doesn’t look good.