Enabling multiple cores in VirtualBox

This post is a follow up to my earlier post Moving from VMWare Player to VirtualBox.

Once you have set up your VirtualBox instance, the first challenge you will face is that the guest OS may possibly be very slow due to the fact that the number of cores allowed is only one. Hence you will have to increase the number of cores that your guest OS can make use of. Open the VirtualBox manager, click on your VM, then click on the Settings button. In the Settings window, click on the System on the left pane and select the Processor tab on the right.
In this page, you can increase the number of processors. If you haven't already enabled the virtualization in your processor, you are likely to get an error when you click on OK. The error message will look like this:


Failed to open a session for the virtual machine Lubuntu.
VD: error VERR_NOT_SUPPORTED opening image file 'C:\VMs\Lubuntu.vmdk' (VERR_NOT_SUPPORTED).
Result Code: E_FAIL (0x80004005)Component: ConsoleInterface: IConsole {db7ab4ca-2a3f-4183-9243-c1208da92392}

If you see this error, you haven't possibly enabled the virtualization in the processor. Virtualization can be enabled only from the BIOS. Please refer to your computer's manufacturer web site to find out how to enable this. For your reference, I am giving a link to how to enable it in ThinkPad W520 (which I own).

Once the virtualization is enabled, you can restart your computer and try to increase the number of cores dedicated your guest OS again. Hopefully, you will not get the same error again.

Thats it. Boot your guest OS and enjoy!

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