VirtualBox serial port setup can be accomplished through the Settings tab or the VBox Manage command. This allows you to create up to four virtual serial ports in each virtual machine. You are required to configure the Port Mode and Port Number. On Mac machines, the connection is made through a local domain socket. Using tmp as the socket. In Proxmox, it just asks what port number but doesn't have any other options such as PIPE or Serial over Ethernet. If you have an adapter, you can pas the USB device to the VM with relative ease. The VM has full control of the device. Much in the same way that you would pass a USB flash drive, mouse, or keyboard.
Map a virtual serial port on the guest(ttyS0) to a pseudo terminal(pty) on the hostThis has to be added to /etc/pve/qemu-server/VMID.conf:
After starting the VM check you will see a message:
Inside the guest, you should see now the serial port:
Inside the guest, you can now instruct systemd to start a login process on the serial port:
From the host you can now start a text terminal to login to the above:
If you don't know where to find the pts terminal, you can also use the qemu monitor to find this:
If you want to get a copy of the boot messages on the text terminal, you can use:
in
/etc/default/grub