full system emulation and user mode emulation.
qemu-x86_64 and qemu-system-x86_64
sudo apt-get install qemu-kvm qemu virt-manager virt-viewer
sudo apt-get install qemu-system
sudo apt-get install qemu-user
//qemu-system-x86_64 -hda linux.img -boot d -cdrom
qemu-img create -f qcow2 ~/QEMU/ubuntu-desktop-18.04.qcow2 10G
qemu-system-x86_64 -boot d -cdrom Porteus-Kiosk-4.9.0-x86_64.iso -m 2048 lubuntu-19.10-desktop-amd64.iso