9 Advanced topics VBoxManage controlvm "VM name" plugcpu 3 VBoxManage controlvm "VM name" unplugcpu 3 See chapter 8.7, VBoxManage modifyvm, page 109 and chapter 8.11, VBoxManage controlvm, page 117 for details. With Linux guests, the following applies: To prevent ejection while the CPU is still used it has to be ejected from within the guest before. The Linux Guest Additions contain a service which receives hot-remove events and ejects the CPU. Also, after a CPU is added to the VM it is not automatically used by Linux. The Linux Guest Additions service will take care of that if installed. If not a CPU can be started with the following command: echo 1 /sys/devices/system/cpu/cpuid/online 9.6 Advanced display configuration 9.6.1 Custom VESA resolutions Apart from the standard VESA resolutions, the VirtualBox VESA BIOS allows you to add up to 16 custom video modes which will be reported to the guest operating system. When using Windows guests with the VirtualBox Guest Additions, a custom graphics driver will be used instead of the fallback VESA solution so this information does not apply. Additional video modes can be configured for each VM using the extra data facility. The extra data key is called CustomVideoModex with x being a number from 1 to 16. Please note that modes will be read from 1 until either the following number is not defined or 16 is reached. The following example adds a video mode that corresponds to the native display resolution of many notebook computers: VBoxManage setextradata "VM name" "CustomVideoMode1" "1400x1050x16" The VESA mode IDs for custom video modes start at 0x160. In order to use the above defined custom video mode, the following command line has be supplied to Linux: vga = 0x200 | 0x160 vga = 864 For guest operating systems with VirtualBox Guest Additions, a custom video mode can be set using the video mode hint feature. 9.6.2 Configuring the maximum resolution of guests when using the graphical frontend When guest systems with the Guest Additions installed are started using the graphical frontend (the normal VirtualBox application), they will not be allowed to use screen resolutions greater than the host’s screen size unless the user manually resizes them by dragging the window, switch- ing to fullscreen or seamless mode or sending a video mode hint using VBoxManage. This be- havior is what most users will want, but if you have different needs, it is possible to change it by issuing one of the following commands from the command line: VBoxManage setextradata global GUI/MaxGuestResolution any will remove all limits on guest resolutions. VBoxManage setextradata global GUI/MaxGuestResolution width,height manually specifies a maximum resolution. VBoxManage setextradata global GUI/MaxGuestResolution auto restores the default settings. Note that these settings apply globally to all guest systems, not just to a single machine. 141
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