QEMU the FAST! processor emulator. What is QEMU? QEMU is a generic and open source machine emulator and virtualizer.
user@workstation:~$ sudo apt-get install -y qemu-kvm qemu virt-manager virt-viewer libvirt-bin
user@workstation:~$ mkdir Virtualization
user@workstation:~$ mkdir Virtualization/Images/
user@workstation:~$ cd Virtualization/Images/
user@workstation:~/Virtualization/Images$ wget http://download.cirros-cloud.net/0.4.0/cirros-0.4.0-x86_64-disk.img
user@workstation:~/Virtualization/Images$ wget https://people.debian.org/~aurel32/qemu/amd64/debian_wheezy_amd64_standard.qcow2
user@workstation:~/Virtualization/Images$ wget http://releases.ubuntu.com/16.04.4/ubuntu-16.04.4-server-amd64.iso
user@workstation:~/Virtualization/Images$ cd ..
user@workstation:~/Virtualization$
user@workstation:~/Virtualization$ qemu-img create -f qcow2 debian.qcow 20G
Formatting 'debian.qcow', fmt=qcow2 size=21474836480 encryption=off cluster_size=65536 lazy_refcounts=off refcount_bits=16
user@workstation:~/Virtualization$ qemu-system-x86_64 -hda debian.qcow -boot d -cdrom Images/ubuntu-16.04.4-server-amd64.iso -m 640
warning: TCG doesn't support requested feature: CPUID.01H:ECX.vmx [bit 5]
user@workstation:~/Virtualization$
user@workstation:~/Virtualization$ qemu-system-x86_64 -smp 4 -m 4096 -boot c -hda debian.qcow
warning: TCG doesn't support requested feature: CPUID.01H:ECX.vmx [bit 5]
warning: TCG doesn't support requested feature: CPUID.01H:ECX.vmx [bit 5]
warning: TCG doesn't support requested feature: CPUID.01H:ECX.vmx [bit 5]
warning: TCG doesn't support requested feature: CPUID.01H:ECX.vmx [bit 5]