Cannot install Ubuntu in VirtualBox due to "this kernel requires an x86-64 CPU, but only detects an i686 CPU, unable to boot" error
I was trying to install Ubuntu 12.04 in VirtualBox 4.2.12r84980. I see
this kernel requires an x86-64 CPU, but only detects an i686 CPU, unable to boot
But I am using a 64 bit Windows 8, and trying same .iso for trying Ubuntu. Then what is the problem?
It does not matter that your host system is 64bit. The whole purpose of a virtual machine is that it is a separate and autonomous machine albeit a virtual one. Edit the virtual machine configuration and change its CPU type to 64bit.
To be able to run a 64-bit OS in Virtual Box we have to make sure the virtual machine's architecture is set to 64-bit too.
Choose Ubuntu 64-bit in General -> Basic settings on creation of your VM
In addition, for running 64-bit guests it is recommended to enable the Input/Output APIC in the System -> Motherboard settings for your virtual machine:
In the System -> Acceleration tab we may want to enable the hardware virtualization features VT-x/AMD-V of your CPU.
On the host system we may have to enable hardware virtualization in the BIOS.
In some systems a host BIOS option to prevent non-trusted execution needs to be turned off (source).
For me even 'Ubuntu (64-bit)' is not listing in dropdown. All OS listing in dropdown are showing '(32-bit)'.
Open the virtual machine settings. Go to the Version dropdown box (General > Basic > Version).
If you don't see "Ubuntu(64 bit)" as an option in the dropdown, it means that virtualization is not enabled on the host.
Reboot the host, go in to BIOS and enable Virtualization. Exit the BIOS, making sure you save changes.
Now, you should see all the 64 bit options in the Version dropdown box.