VirtualBox

VirtualBox is a free means to create and manage VirtualMachines.
It's compatible with Windows, Linux, and Mac systems.

Installing VirtualBox

Follow the steps on the VirtualBox Downloads page.

Ubuntu comes with a repository of VirtualBox included, but the version it pulls is generally fairly outdated. It can be installed with:

To use a repository that uses current versions of VirtualBox, run the commands:

wget -q https://www.virtualbox.org/download/oracle_vbox_2016.asc -O- | sudo apt-key add -
sudo add-apt-repository "deb [arch=amd64] http://download.virtualbox.org/virtualbox/debian $(lsb_release -cs) contrib"
sudo apt update && sudo apt install virtualbox-<version>
- Where <version> is the latest version of VirtualBox available. You should be able to just tab complete in the terminal to see versions available.

Download the iso for your desired operating system.
Setup a new VM and run through the standard OS setup process.
Remember to proper memory, processors, and vram, otherwise it may run poorly/incorrectly.
- For example, VMs running Ubuntu18 may black screen if only allocated the default 16 MB vram.
Once installed, launch the VM and:
- Install the Guest Editions CD through the menu with Devices > Insert Guest Editions CD Image...
- Run normal system updates on your VM.
Finally, restart the VM to be ready for normal use.

To make use of Guest Editions in ubuntu a few additional steps might be needed.

Install additional apt dependencies on the VM:
- sudo apt install build-essential dkms
Add the logged in user to the VirtualBox group:
- sudo usermod -a -G vboxsf <user_name>