When working with Linux CLI-only virtual machines, the default noVNC console is often inconvenient for pasting long commands, scripts, Docker Compose files, or cloud-init configurations.

A better option is to use a Serial Console with xterm.js, which provides a terminal-like experience directly in the Proxmox web interface and allows reliable copy-and-paste operations. This is especially useful for cloud images and minimal Linux installations that do not have a graphical environment.

Why Use a Serial Console?

Benefits:

  • Copy and paste long commands directly into the VM
  • Works without a graphical desktop
  • Faster than noVNC for terminal work
  • Useful when network connectivity or SSH are broken
  • Similar to SSH terminal behavior
  • Easier to capture boot messages and troubleshooting output

Configure the VM Hardware

From the Proxmox host, ensure the guest VM is off and then edit:

#!/bin/bash
qm set [VMID] --serial0 socket

Example:

#!/bin/bash
qm set 200 --serial0 socket

#--output:
update VM 200: -serial0 socket

The above commands accomplished the following tasks:

  • Adds a virtual serial port (serial0)
  • Sets the VM display to use the serial console
  • Causes the Proxmox Web Console to use xterm.js instead of the traditional noVNC display.
qm set [VMID] --serial0 socket --vga serial0 is not needed, display type does not need to be changed.

Configure Linux Guest for Serial Console

Turn on the Linux VM, Edit GRUB:

#!/bin/bash
sudo nano /etc/default/grub

Find:

#!/bin/bash
GRUB_CMDLINE_LINUX_DEFAULT="quiet"

Change to:

#!/bin/bash
GRUB_CMDLINE_LINUX_DEFAULT="quiet console=tty0 console=ttyS0,115200"

Update GRUB:

Debian / Ubuntu

#!/bin/bash
sudo update-grub

RHEL / Rocky / AlmaLinux

#!/bin/bash
sudo grub2-mkconfig -o /boot/grub2/grub.cfg

Reboot:

#!/bin/bash
sudo reboot

This instructs Linux to send console output to both the normal display and the virtual serial port.

Using xterm.js in Proxmox

After the VM reboots:

  1. Open the VM in Proxmox.
  2. Click Console on the top-right corner.
  3. Select xterm.js from the drop down.

You may initially see:

#!/bin/bash
starting serial terminal on interface serial0

Simply press Enter to obtain a login prompt.

Connect from the Proxmox Host CLI

You can access the VM serial console directly from the Proxmox shell or SSH:

#!/bin/bash
qm terminal [VMID]

Example:

#!/bin/bash
qm terminal 100

Output:

#!/bin/bash
starting serial terminal on interface serial0

Press Enter and log in normally.

To disconnect:

#txt
Ctrl + O

If using another serial interface:

#!/bin/bash
qm terminal 100 --iface serial1

Verify Serial Console Configuration

Check the VM configuration:

#!/bin/bash
qm config [VMID]

#Expected output:
serial0: socket

You can also verify the serial device from the Proxmox host:

#!/bin/bash
qm monitor [VMID]

Then:

#!/bin/bash
info chardev

You should see something similar to:

#!/bin/bash
serial0: filename=disconnected:unix:/var/run/qemu-server/[VMID].serial0

Reference

Links:

https://pve.proxmox.com/wiki/Serial_Terminal