8 VBoxManage • --hardwareuuid uuid: The UUID presented to the guest via memory tables (DMI/SMBIOS), hardware and guest properties. By default this is the same as the VM uuid. Useful when cloning a VM. Teleporting takes care of this automatically. • --cpus cpucount: This sets the number of virtual CPUs for the virtual machine (see chapter 3.4.2, “Processor” tab, page 44). If CPU hot-plugging is enabled (see below), this then sets the maximum number of virtual CPUs that can be plugged into the virtual ma- chines. • --rtcuseutc on|off: This option lets the real-time clock (RTC) operate in UTC time (see chapter 3.4.1, “Motherboard” tab, page 43). • --cpuhotplug on|off: This enables CPU hot-plugging. When enabled, virtual CPUs can be added to and removed from a virtual machine while it is running. See chapter 9.5, CPU hot-plugging, page 140 for more information. • --plugcpu|unplugcpu id: If CPU hot-plugging is enabled (see above), this adds a virtual CPU to the virtual machines (or removes one). id specifies the index of the virtual CPU to be added or removed and must be a number from 0 to the maximum no. of CPUs configured with the --cpus option. CPU 0 can never be removed. • --cpuexecutioncap 1-100: This setting controls how much cpu time a virtual CPU can use. A value of 50 implies a single virtual CPU can use up to 50% of a single host CPU. • --synthcpu on|off: This setting determines whether VirtualBox will expose a synthetic CPU to the guest to allow live migration between host systems that differ significantly. • --pae on|off: This enables/disables PAE (see chapter 3.4.2, “Processor” tab, page 44). • --hpet on|off: This enables/disables a High Precision Event Timer (HPET) which can replace the legacy system timers. This is turned off by default. Note that Windows supports a HPET only from Vista onwards. • --hwvirtex on|off: This enables or disables the use of hardware virtualization exten- sions (Intel VT-x or AMD-V) in the processor of your host system see chapter 10.3, Hard- ware vs. software virtualization, page 157. • --hwvirtexexcl on|off: This specifies whether VirtualBox will make exclusive use of the hardware virtualization extensions (Intel VT-x or AMD-V) in the processor of your host system see chapter 10.3, Hardware vs. software virtualization, page 157. If you wish to simultaneously share these extensions with other hypervisors, then you must disable this setting. Doing so has negative performance implications. • --nestedpaging on|off: If hardware virtualization is enabled, this additional setting enables or disables the use of the nested paging feature in the processor of your host system see chapter 10.3, Hardware vs. software virtualization, page 157. • --largepages on|off: If hardware virtualization and nested paging are enabled, for Intel VT-x only, an additional performance improvement of up to 5% can be obtained by enabling this setting. This causes the hypervisor to use large pages to reduce TLB use and overhead. • --vtxvpid on|off: If hardware virtualization is enabled, for Intel VT-x only, this addi- tional setting enables or disables the use of the tagged TLB (VPID) feature in the processor of your host system see chapter 10.3, Hardware vs. software virtualization, page 157. • --accelerate3d on|off: This enables, if the Guest Additions are installed, whether hard- ware 3D acceleration should be available see chapter 4.4.1, Hardware 3D acceleration (OpenGL and Direct3D 8/9), page 64. 110