Ensure that "Intel VT-x" or "AMD-V" is enabled in your physical computer’s BIOS/UEFI settings, or the VM will not boot. Best Practices for Security and Performance
Explain how to between your main computer and the VM ubuntu virtual machine image
Before booting, allocate at least 2GB of RAM (4GB for Desktop versions) and 2 CPU cores for smooth performance. Ensure that "Intel VT-x" or "AMD-V" is enabled
virt-install --name ubuntu-vm --ram 2048 --disk size=20 --network bridge=virbr0 --cdrom /path/to/ubuntu-20.04-desktop-amd64.iso ubuntu virtual machine image