This guide by Linux Commando will show you how to test out FreeBSD on a virtual machine in Debian. For Linux users interested in trying out FreeBSD, check out this guide to get started.

Using VirtualBox to build FreeBSD VM on Debian

Many virtualization software (aka hypervisors) can run on the host operating system of Linux. Notable open-source software include VirtualBox, KVM, and Xen. This post outlines how to 1) install VirtualBox on Debian 9 (Stretch), and 2) build a FreeBSD virtual machine.

Prepare for installation

Perform the following steps prior to installing VirtualBox:

1. Enable virtualization technology in BIOS.

2. Download FreeBSD ISO.

Enable virtualization in BIOS …

Full tutorial: https://linuxcommando.blogspot.com/2017/12/using-virtualbox-to-build-freebsd-vm-on.html