Starting with release 3.1, VirtualBox includes experimental support for the Extensible Firmware Interface (EFI), which is a new industry standard intended to eventually replace the legacy BIOS as the primary interface for bootstrapping computers and certain system services later.
By default, VirtualBox uses the BIOS firmware for virtual machines.
To use EFI for a given virtual machine, you can enable EFI in the
machine's "Settings" dialog (see Section 3.5.1, “"Motherboard" tab”).
Alternatively, use the VBoxManage command
line interface like this:
VBoxManage modifyvm "VM name" --firmware efi
To switch back to using the BIOS, use:
VBoxManage modifyvm "VM name" --firmware bios
One notable user of EFI is Apple's Mac OS X, but more recent Linuxes and Windows (starting with Vista) offer special versions that can be booted using EFI as well.
Another possible use of EFI in VirtualBox is development and testing of EFI applications, without booting any OS.
Note that the VirtualBox EFI support is experimental and will be enhanced as EFI matures and becomes more widespread. Mac OS X, Linux and newer Windows guests are known to work fine. Windows 7 guests are unable to boot with the VirtualBox EFI implementation.
EFI provides two distinct video interfaces: GOP (Graphics Output Protocol) and UGA (Universal Graphics Adapter). Modern operating systems (such as Mac OS X) generally use GOP, while some older ones still use UGA. VirtualBox provides a configuration option to control the graphics resolution for both interfaces, making the difference mostly irrelevant for users.
The default resolution is 1024x768. To select a graphics resolution
for EFI, use the following VBoxManage
command:
VBoxManage setextradata "VM name" VBoxInternal2/EfiGraphicsResolution HxV
Determine the horizontal resolution H and the vertical resolution V from the following list of default resolutions:
- VGA
-
640x480, 32bpp, 4:3
- SVGA
-
800x600, 32bpp, 4:3
- XGA
-
1024x768, 32bpp, 4:3
- XGA+
-
1152x864, 32bpp, 4:3
- HD
-
1280x720, 32bpp, 16:9
- WXGA
-
1280x800, 32bpp, 16:10
- SXGA
-
1280x1024, 32bpp, 5:4
- SXGA+
-
1400x1050, 32bpp, 4:3
- WXGA+
-
1440x900, 32bpp, 16:10
- HD+
-
1600x900, 32bpp, 16:9
- UXGA
-
1600x1200, 32bpp, 4:3
- WSXGA+
-
1680x1050, 32bpp, 16:10
- Full HD
-
1920x1080, 32bpp, 16:9
- WUXGA
-
1920x1200, 32bpp, 16:10
- DCI 2K
-
2048x1080, 32bpp, 19:10
- Full HD+
-
2160x1440, 32bpp, 3:2
- Unnamed
-
2304x1440, 32bpp, 16:10
- QHD
-
2560x1440, 32bpp, 16:9
- WQXGA
-
2560x1600, 32bpp, 16:10
- QWXGA+
-
2880x1800, 32bpp, 16:10
- QHD+
-
3200x1800, 32bpp, 16:9
- WQSXGA
-
3200x2048, 32bpp, 16:10
- 4K UHD
-
3840x2160, 32bpp, 16:9
- WQUXGA
-
3840x2400, 32bpp, 16:10
- DCI 4K
-
4096x2160, 32bpp, 19:10
- HXGA
-
4096x3072, 32bpp, 4:3
- UHD+
-
5120x2880, 32bpp, 16:9
- WHXGA
-
5120x3200, 32bpp, 16:10
- WHSXGA
-
6400x4096, 32bpp, 16:10
- HUXGA
-
6400x4800, 32bpp, 4:3
- 8K UHD2
-
7680x4320, 32bpp, 16:9
If this list of default resolution does not cover your needs, see Section 9.8.1, “Custom VESA resolutions”. Note that the color depth value specified in a custom video mode must be specified (8, 16, 24 and 32 are accepted), but it is silently assumed to be 32 by EFI.
The EFI default video resolution settings can only be changed when the VM is powered off.
It is currently not possible to manipulate EFI variables from within a running guest
(e.g., setting the "boot-args" variable by running the nvram tool in a Mac OS X guest will not work).
As an alternative way, "VBoxInternal2/EfiBootArgs" extradata can be passed to a VM in order to set
the "boot-args" variable. To change the "boot-args" EFI variable:
VBoxManage setextradata "VM name" VBoxInternal2/EfiBootArgs <value>