I made a Linux Ubuntu 16.04 VDI image on VirtualBox on an Intel i7 machine (4 CPUs), with a set of tools inside. Then I copied that VDI to an old machine (Core 2 duo - 2 CPUs), I created the VM using the VDI file copy. The image boots, but runs very slowly with 1 CPU (which is obvious).

The problem now is that when I use all the 2 cores (in the older machine) the virtual machine doesn't boot, it displays the GRUB page, then a black screen (with a blinking cursor _ ). Yet, the boot succeeds in the i7 machine with any number of cores (1-4). Is there something I missed?


Is VT-X enabled on the old machine? Is it even supported? (likely disabled by default even if supported). Running with one processor is slow but bearable, running without VT-X limits you to one processor and is much slower.

  • 1
    Yes it is enabled. The awkward thing is that I had an old image which was booting fine on 2 CPUs on the old machine. But for this image this is not the case :( – noureddine-as Nov 14 '18 at 8:47
  • Was the old image perhaps a 32 bits version of Linux? – wurtel Nov 14 '18 at 15:19

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