how to boot from a virtual machines disk
 

I've installed a virtual machine on my computer. and I want to boot from its hard disk(which is on my /home/xen/domains/test1/disk.img). what I need is create a grub entry for this. please tell me the steps

By /home/xen/domains/test1/disk.img I may assume you are using Xen for Virtualization.

If you have already installed the VM, then boot it by pressing POWERON button if you are using Virtual machine manager. I could not really understand what is your difficulty in switching on the VM ?

You need to boot through xen kernel when your machine boots.

Please try to give more details about your problem. By the by which distro are you using ?

Do you mean that you want to boot the .img file on the real hardware?

Since I am confused a bit here, lemme ask this.

Are you trying to get the img to boot when the computer powers on?

Yes. Is there a way to do that ?

To the best of my knowledge it is not possible.

ISOLinux offers some the ability to boot from a Linux hard drive image. I am not sure if you could manipulate it to boot your VM image but i think it is about your best shot.

If it can be done, there may be issues with the OS in the .img file finding itself running on different hardware depending on whether it is booted in the real computer or a virtual machine. If the OS is Windows, these issues will be significant; if it is Linux it will probably be OK perhaps with a few small adjustments, depending on how generic the kernel is. It would be prudent to back up the .img file before experimenting.

theoretically possible but probably not feasable, though if the /boot partition and initrd were on a real partition maybe possible in theory if you could make linux think the disk image were a block device but probably would require far more work then it's worth to accomplish if even possible

Might look at grubfdos. I know it can boot iso's on a usb so I guess it could boot a similar image on a hard drive.

how ubuntu boots inside windows
 

Ok. Do any one know how ubuntu boots when it is installed inside windows. If you have installed like that please post the menu.lst or grub.cfg so we can see how it is done in grub.

A lot of information here. Ask again if you get stuck.