Changing the resolution of an Ubuntu guest in a Hyper-V host

Ensure the system is updated
sudo apt-get update

1. Delete the monitor configuration
sudo rm ~/.config/monitors.xml

2. Set the startup resolution
sudo vi /etc/default/grub
Set GRUB_CMDLINE_LINUX_DEFAULT="quiet splash video=hyperv_fb:1680x1050" (or whatever)

3. Update grub
sudo update-grub