Virtualization: Windows Host & Ubuntu Guest, but be able to dual-boot and select the guest

Question

This very well may not work as I intend it to.

Due to the nature of my research, some things are easy in Windows and hard on Linux and other things are easy on Linux and hard on Windows. What I'd like to do is have a dual-boot setup where I can access my Ubuntu "VM" as either from VirtualBox in Windows 7 or selecting it at boot.

Before I go off on the deep end and try to get this to run, I'd like to bounce some ideas off people. My first idea is to start with:

 30G   NTFS  Windows 7 boot partition
500M   ext2  Ubuntu  /boot & /etc partition
190G   NTFS  "Applications & Program Data" Partition

Then I can boot the the 30G NTFS partition, set c:/Users, c:/Program Files* to point to subdirs on the 190G partition. Then I can boot the 500M Ubuntu partition and use FUSE to mount / from the 190G partition.

Now I can setup a Ubuntu VirtualBox guest on Windows 7. I pull the same trick and get / mounted from the 190G partition. That way, the size of the virtual disk is quite small, and only really contains virtualization specific things.

So my question is: which of the directories under / do I need to keep separate in the two instances? My assumption is /boot and /etc any others? Will this work at all?

Cheers,

Nathan

Answer 1

Assuming that VirtualBox allows you to use the real-machine partition as a virtual-machine partition or disk, you can boot the same Linux installation indifferently in the VM or on the real hardware. Live CDs do it all the time, and it's not particularly constraining. (As far as I know, this is a lot harder to achieve for Windows.)

If the partition layout is different, you'll have to have separate bootloaders, or at least separate bootloader configurations. You don't even need to actually separate /boot from the main installation: leave it in, set it up properly for direct booting, and use a different bootloader (such as a standalone Grub (virtual) floppy) in the VM.

You might want some settings (e.g. network configuration) to be different depending on whether you're running on the hardware or in the VM. You can test whether the system is running inside VirtualBox with VBoxControl.

Linux loads most drivers automatically. The only common exception is proprietary video drivers, which might require you (or an automated setup program) to write a brand-specific /etc/X11/xorg.conf. You can get the X server to read a different configuration file with its -config option or with the XORGCONFIG environment variable.

If VirtualBox doesn't allow using the real-machine partition directly inside the VM, you might have to resort to mounting the root filesystem over vboxvfs. This requires an initrd containing the VirtualBox kernel modules, which you can build with update-initramfs.