BackBox Linux is a free, open-source community project based on Ubuntu. Find out how to use the BackBox Linux distribution as a virtual machine. Several Linux distributions are available nowadays for ...

Qubes OS defines itself modestly as “a reasonably secure operating system.” It might actually be one of the safest operating systems, often used by pros who are most concerned with computer security.

If you need to use virtual machines on Linux, try Virt-Manager. Virt-Manager is more reliable than VirtualBox. Virt-Manager is completely free and open-source. I'm a long-time supporter of VirtualBox.