PBS on device with ONLY a serial console (no video)

lmm5247

Active Member
May 21, 2020
29
13
43
I have an OPNsense DEC740 that I'm trying to install PBS onto (the manufacturer doesn't support anything other than OPNsense).

This device uses a Ryzen V1500B embedded CPU and has no video output, only serial console via USB. The device shows up in Linux as Bus 001 Device 019: ID 04e2:1411 Exar Corp. XR21B1411 UART.

In the BIOS, I have these settings for the serial console.
Code:
                                                    InsydeH2O Setup Utility                                             Rev. 5.0
                                                  AMD CBS                                                                     
/-------------------------------------------------------------------------------------+----------------------------------------\
|Uart Configuration Options                                                           |No help string                          |
|                                                                                     |                                        |
|Uart 0 Enable                              <Enabled>                                 |                                        |
|Uart 0 Legacy Options                      <COM1 0x3F8>                              |                                        |
|Uart Driver Type                           <AMD Serial Driver>                       |                                        |

If I boot PBS flashed to a USB drive with dd, I only see this. I never get to the PBS boot screen.
Code:
error: file `/boot/' not found.

However, if I flash Ventoy to the USB drive, I can copy the PBS ISO to Ventoy and boot to the Ventoy menu.
Code:
                             GNU GRUB  version 2.04

 /----------------------------------------------------------------------------\
 |*proxmox-backup-server_4.0-1.iso                                            |
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 \----------------------------------------------------------------------------/

      Use the ^ and v keys to select which entry is highlighted.
      Ventoy 1.1.07 UEFI  www.ventoy.net
      L:Language  F1:Help  F2:Browse  F3:TreeView  F4:Localboot  F5:Tools
    F6:ExMenu

Booting in "normal mode" does nothing (literally a black screen)...
Code:
                             GNU GRUB  version 2.04

 /----------------------------------------------------------------------------\
 |*Boot in normal mode                                                        |
 | Boot in grub2 mode                                                         |
 | File checksum                                                              |
 | Return to previous menu                                                    |
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 \----------------------------------------------------------------------------/

      Use the ^ and v keys to select which entry is highlighted.

If I use "grub2 mode", I see these two options.
Code:
                             GNU GRUB  version 2.04

 /----------------------------------------------------------------------------\
 |*Install Proxmox Backup Server (Graphical)                                  |
 | Install Proxmox Backup Server (Terminal UI)                                |
 | Advanced Options                                                           |
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 \----------------------------------------------------------------------------/

      Use the ^ and v keys to select which entry is highlighted.

Choosing "Terminal UI" shows this, then nothing else happens...
Code:
Loading Proxmox Backup Server Console Installer ...
Loading initial ramdisk ...

The only option that does anything is going to Advanced and choosing "Serial Console Debug Mode".
Code:
                             GNU GRUB  version 2.04

 /----------------------------------------------------------------------------\
 | Install Proxmox Backup Server (Debug Mode)                                 |
 | Install Proxmox Backup Server (Terminal UI, Debug Mode)                    |
 |*Install Proxmox Backup Server (Serial Console Debug Mode)                  |
 | Install Proxmox Backup Server (Automated)                                  |
 | Rescue Boot                                                                |
 | Test memory (memtest86+)                                                   |
 | UEFI Firmware Settings                                                     |
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 \----------------------------------------------------------------------------/

      Use the ^ and v keys to select which entry is highlighted.

That eventually boots Linux and gets me to the installer (I can't copy/paste terminal output here, so this is a screenshot). My question is, why does this work with Ventoy but not the PBS ISO?
Screenshot_20251013_172155.png

From the docs, I see this. Is there a way to set this by editing the USB drive flashed directly with dd? It seems dumb to have to use Ventoy to install PBS, when PBS should be able to do this. I can't set nomodeset, because I never get to the Proxmox boot menu...
Advanced Options: Install Proxmox Backup Server (Serial Console Debug Mode)

Same the terminal-based debug mode, but additionally sets up the Linux kernel touse the (first) serial port of the machine for in- and output.