VirtualBox

VirtualBox is cross-platform virtualization software that allows users to run guest operating systems inside a host operating system without having to reboot. Since 2010 VirtualBox software has been written and maintained by the Oracle Corporation.

Installation
There is a source based package and a binary package  available in the Portage tree. The binary version is available so 64bit no-multilib users can use VirtualBox, too. The binary package contains some extensions which are not available in the source package. To get identical functionality with the source package, emerge it with the  USE being enabled.

The  USE controls installation of the graphical user interface (GUI) which is enabled by default.

4.x.x
When using VirtualBox versions < 5.0.0, it is possible to enable the  USE when installing VirtualBox on the host system to get the ISO image that contains all necessary Windows guest drivers.

5.x.x
Starting with versions >= 5.0.0, emerge the package for Windows guest additions extensions:

Linux guest-related
In order to run Gentoo as a guest system, invoke the following command in the Gentoo guest operating system:

To enable the shared clipboard, display resizing, seamless mode and drag and drop make sure the user running the X.org session belongs to the group.

Changes will not take effect until the user signs out and then signs in again (re-logins).

To install other Linux distributions as guest operating systems please refer to the distribution's documentation on how to install the drivers needed by VirtualBox or consult the official VirtualBox documentation.

VirtualBox shared folders in a Gentoo guest
VirtualBox shared folders can only be mounted after the virtualbox-guest-additions service has been started. Since this happens towards the end of the bootup sequence (OpenRC), a shared folder mount in will fail. Either:
 * make the mount noauto and add a mount/unmount pair of scripts in
 * or see for information about adding extra dependencies for services

Advanced networking-related
According to the ebuild's message after VirtualBox is installed and  can be installed for advanced network configuration. Install them only if advanced networking is required:

Kernel modules
Users will not be able to run and use VirtualBox if they are not a member of the group:

Changes will not take effect until the user re-login.

Load the required driver module into the kernel. This module is made available when has been emerged:

Optional modules:

OpenRC
When using OpenRC it is possible to automatically load the modules each time the system boots. Edit the file by adding the following VirtualBox modules:

Systemd
When using Systemd, a similar approach can be taken. Create a new file under the directory and list, separated by newlines, the kernel modules to load:

Usage
There are many options which can influence behavior and performance of the virtual machines. If you don't know what these options are doing, leave them to their defaults. Virtual machines may become unbootable if the wrong options are set.

Here is a list of options that are safe to use:
 * Host I/O cache can safely be enabled for all virtual storage controllers.
 * If the host system's CPU supports hardware virtualization, enable the 'VT-x/AMD-V' option. It can drastically increase the performance of the virtual machines.

virtualbox fails to build
When the package fails to build because the  command cannot be found (even with a Java JDK (Java Development Kit) and a Java JRE (Java Runtime Environment) installed), it is likely the JRE has been set as the default system-vm. JRE packages do not contain. Make sure the correct system-vm (JDK) has been selected using the command and then try rebuilding virtualbox. More information can be found in the Configuring the Java Virtual Machine section of the Java article.

virtualbox-modules fails to build
Some users have issues with the package failing to build. This can be caused by an improper kernel/profile configuration. Verify the chosen kernel and the selected profile match each other. For example, if a hardened profile is set, a hardened kernel should be used. If a default AMD64 profile is set, then the default gentoo-sources should be used. Run the command to view the list of profile options:

Then use the command again to display which kernel is selected:

Looking at the output of these two commands, a user can determine if the system is setup properly (the profile matches the kernel) and should have no issues installing. Remember: Make sure the system profile and the selected kernel match!

Microsoft Windows guests

 * Do not enable APIC for Microsoft Windows guests! VirtualBox also has a bad habit of enabling this option on its own will. The fix is to select the System Processor Driver (i.e. ACPI Uniprocessor PC) and manually upgrade (change) to the Advanced Configuration and Power Interface (ACPI) PC. Shutdown (not reboot), restart VirtualBox and ensure APIC is off, then boot the guest. As usual, always make a backup before playing with Windows.
 * Using a SATA controller, it is necessary to choose the right driver version from Intel's SATA drivers. Using a wrong version will cause performance problems along with blue screen errors! Refer to this post for a list of working SATA drivers.
 * Slow performance using SATA driver? Only use the SATA controller interface for the hard disk. Remove any CDROMs from the SATA controller and place them onto a IDE Controller.
 * When installing the VirtualBox Guest Additions into your Windows operating system, do not select to enable Direct3D (experimental) option as this will cause resizing problems and other anomalies. Also, you need to install the Guest Additions from Safe Mode.
 * Do not use the ICH9 chipset with Windows. It is still considered experimental. Using it can cause temporary freezes of the whole VM when used with Windows 7. See this post for more informations.
 * Slow read/write speed to the virtual disk? If the host system has sufficient RAM, try checking (enabling) the check box in the virtual machine's  frame. This will cache much of the guest machine's page file into the host's memory effectively limiting the amount of I/O guest machine will use the virtual disk image file. This is particularly helpful when running Windows guests because of the amount of paging Windows based operating systems regularly perform.

Linux guests

 * When running Gentoo as a guest system make sure you start the virtualbox-guest-additions init script during bootup.

Kernel driver not installed


This may occur after building a new kernel and causes an error message:


 * Kernel driver not installed (rc=-1908)


 * The VirtualBox Linux kernel driver (vboxdrv) is either not loaded or there is a permission problem with /dev/vboxdrv. Please reinstall the kernel module by executing


 * '/etc/init.d/vboxdrv setup'


 * as root. If it is available in your distribution, you should install the DKMS package first. This package keeps track of Linux kernel changes and recompiles the vboxdrv kernel module if necessary.

Solution: Rebuild the VirtualBox kernel modules with

You may need to restart your computer to validate the change.

Nonexistent host networking interface, named 'vboxnet0'
Newly created interface will not be shown with ifconfig. You will have to assign some IP to it:

External resources

 * vboxweb_rb - Web-based administration utility (Ruby)
 * VirtualBox Manual