Check Virtualization Extension 

Run this command to make sure you’ve enabled virtualization in on your computer. It should be above 0

titus@debian:~$  egrep -c '(vmx|svm)' /proc/cpuinfo
12

If the output is zero then go to bios settings and enable VT-x (Virtualization Technology Extension) for Intel processor and AMD-V for AMD processor.

Install QEMU and Virtual Machine Manager

titus@debian:~$ sudo apt install qemu-kvm libvirt-clients libvirt-daemon-system bridge-utils virtinst libvirt-daemon virt-manager -y

Verify that Libvirtd service is started

titus@debian:~$ sudo systemctl status libvirtd.service

**
Start Default Network for Networking
**

VIRSH is a command to directly interact with our VMs from terminal. We use it to list networks, vm-status and various other tools when we need to make tweaks. Here is how we start the default and make it auto-start after reboot. 

titus@debian:~$ sudo virsh net-start default
Network default started
titus@debian:~$ sudo virsh net-autostart default
Network default marked as autostarted

Check status with:

titus@debian:~$ sudo virsh net-list --all
 Name      State      Autostart   Persistent
----------------------------------------------
 default   active       yes          yes

Add User to libvirt to Allow Access to VMs

titus@debian:~$ sudo adduser titus libvirt
titus@debian:~$ sudo adduser titus libvirt-qemu

Reboot and you are Finished!