Virtual only machine?

Hi dudes and dudettes,

I was asked a question yesterday about Type 1 Virtual Machine software. Basically the user wants to have a computer with no OS running but boot up and be able to choose from a list of virtual machines to run. From my infinite knowledge (Wikipedia) I think this is a type 1 hypervisor or Kernel-based Virtual Machine (KVM).

I have a fair bit of experience with VMs using VirtualBox on my desktop to test new distros etc…

Does anyone here have any insight or advice on a Virtual only machine as explained above? I read about Xen and I will have a play around with it myself but any help would be appreciated.

Cheers in advance!

I believe KVM is what they’re looking for, although really the man to ask is Mad Penguin IMO. That guy has more virtual machines than hot dinners. :stuck_out_tongue:

As I understand it, he HAS to have an OS, or how would xen/kvm run ? … just that they can sidestep the host OS and access the hardware directly … kind of.

I’ll see if I can draw MP’s attention to this topic :wink: … as BkS suggests, he’s “the man” for this kinda stuff :slight_smile:

Or do you mean something like a WUBI install seems to do … which is really just dual booting, but using a “virtual drive” ?

I think it’ll be OK if there is a host OS with Virtual Machines on top but if that’s the case is is possible to boot directly into one of the VMs without logging into the host system.

For example a computer with a Linux host OS. On boot up you can choose either to access the host or boot a VM, say Windows, from a menu. Almost like a dual boot setup but with Virtual Machines.

I’m not sure why the guy wants to do this but I like learning as well so it would be interesting to find out.

I’ve drawn MP’s attention to this topic …

I’d assume the answer is yes, but the “host” (probably the wrong word) os must be running … sounds to me like VM isn’t what he’s after … unless I’m mistaken.

Sounds more like he want, multiple boot (maybe without separate partitions), with virtual drives … like WUBI does it.

But lets wait see what MP has to say

I’ll check that out, cheers Mark.

While you are waiting for MP you could check this out:

Had this link for a while (I was going to look into virtualising windows without the kids knowing) but it fallen on the wayside
It is based on Ubuntu server.

Cheers SeZo, I’ll have a look.

Mmm, it sounds more like he’s looking for a multi-boot system rather than VM’s (!)
You can install multiple OS’s in parallel, then have the machine offer a boot menu that will boot your chosen OS.
[this is a function of the “GRUB” bootloader]

VM’s are a little different in that you boot the OS (whether this be a real OS or a hypervisor), then you can run a number of instances of a.n.other operating system on top, in parallel.

In Xen speak , you would boot the machine into the OS which would be Xen Dom0, which is a cut-down / bastardized version of the Linux kernel, or with KVM you’d boot a standard Ubuntu (or whatever) kernel. Then in either instance you could run one or more instances of other Operating Systems on top.

Note :: XEN has one use and one use only, it runs on pre HVM machines, i.e. kit that's typically > 3-4 years old. You'd either have to have a very specific technical reason to run it in preference to KVM, or some really old kit, or a common sense deficiency ... ;)

General outline of how to get a Windows instance up using KVM on an Ubuntu machine;

Make sure you have “kvm” and “virt-manager” installed.
Insert your windows install disk and do;

dd if=/dev/cdrom of=/var/lib/libvirt/images/windows.img bs=1M

Run virt-manager, connect to the local machine, create a new instance, select windows.img as the “install CD”, create yourself a virtual disk, follow the instructions and it should get the VM running. Double click on the entry in virt-manager and it should present a console showing the Windows installation screen … then just install as you would a normal Windows machine … albeit a Windows machine running in a Window.

Cheers MP.

I explained to him about using dualboot and running VMs on his PC, say using VirtualBox.

I’ll have a look at KVM and see if that’s what he is after. If not… I’ll try and get a clearer explanation. It might be that he doesn’t really understand.

Thanks for all the help any way guys!

KVM will almost certainly be quicker than VBox/VMware, but will require a CPU that supports hardware accelerated virtualisation.

I think that’s what MP meant by

Note :: XEN has one use and one use only, it runs on pre HVM machines