Proxmox VE xterm.js (Serial Terminal) for Arch Linux VM

pve_xtermjs_for_arch_vm.txt

1. Add a virtual serial port to the VM using PVE Web GUI and restart the VM

2. Config grub
When using GRUB with a generated grub.cfg, edit /etc/default/grub and enable serial input and output support:

/etc/default/grub
...
GRUB_TERMINAL_INPUT="console serial"
...
GRUB_TERMINAL_OUTPUT="gfxterm serial"
...
Next add the GRUB_SERIAL_COMMAND variable and set the options for the serial connection. For COM1 (/dev/ttyS0) with baud rate of 115200 bit/s:

/etc/default/grub
...
GRUB_SERIAL_COMMAND="serial --unit=0 --speed=115200"


3. Enable and start the virtual serial port on VM, change tty number as needed (Reference: 
$ sudo systemctl enable serial-getty@ttyS0.service
$ sudo systemctl start serial-getty@ttyS0.service

4. Done! You can now select xterm.js in the PVE Web GUI

To enable auto-reszie:

1. Install xterm
2. Add following setting to .bashrc

alias rsz='resize >/dev/null'
if [ $(tty) == '/dev/ttyS0' ]; then
trap rsz DEBUG
export TERM=xterm
fi

For fish shell:

function rsz
    resize > /dev/null
end

if test (tty) = "/dev/ttyS0"
    function resize_on_command
        rsz
    end

    # Set up an event handler to run before every command execution
    functions -e fish_preexec # Remove if it already exists
    function fish_preexec --on-event fish_preexec
        resize_on_command
    end

    set -gx TERM xterm
end

3. Use command resize to manually resize serial window size.