Oracle's VirtualBox runs on Windows, Linux and MacOS desktops and supports a variety of Intel host operating systems including Windows, Linux and MacOS. The core product is free and open source software licensed under GPLv2.
By default, VirtualBox sets up news guests on a private internal network that communicates with the outside world through the host's network interface using NAT.
There are VM specific hardware drivers for most guests that can be installed by mounting the built-in Guest Additions CD, which is distinct from the proprietary VirtualBox Extensions Pack.
Installation of the guest additions is recommended even for "headless" guests.
After installing the guest additions the guest's display configuration should be modified to use the VBoxSVGA graphics controller, with 3D Acceleration enabled and Video Memory maxed out (depending on the O/S this will be either 128 or 256 MB).
As a rule of thumb, set the guest's resources to no more than 1/2 the host's CPU cores and RAM.
USB 2.0 and 3.0 support requires the VirtualBox Extensions Pack. Without this, only USB 1.0 will be available.
Although it is not as polished as rival VMware Workstation, VirtualBox is more user-friendly than KVM/libvirt for Linux.
Installations of the Vagrant development environment often use VirtualBox for their virtualization layer.
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