It is very helpful to use an emulator with disk images to test code. We use bochs. It is also convenient to use a bootloader. We use grub. The osdever tutorial is useful, but doesn't really lay out how to do this. I've found a single harddisk image with both grub and my kernel image a useful route. I depended on a few sources, but this one was particularly helpful.

To get this started, I downloaded, compiled, and installed bochs. I leave this as an exercise for the reader. Next, I used the bochs image builder, bximage, to build a harddisk image:

If you choose a different size, it is important to note the number of cylinders reported by bximage. Next, you need to "partition" the disk image. Happily, with a little help, fdisk will work on files:

Notice that we pass the disk geometry directly to fdisk on the command-line. Nobody seems to believe that setting the disk as bootable is necessary, but everybody seems to do it, so I do as well. We next use the Linux loopback facility to mount the image as a disk and create a filesystem. To do this, you must have kernel support for it, but many distributions seem to include it in their standard kernels by default. Also, I use losetup to attach the file to the loopback device. The '32256' is after the first track (512 bytes/sector * 63 sectors/track). According to some sources, this is necessary because fdisk want to leave the entire first track for the master boot record. Also, apparently, some bootloaders (grub included) use the first track for multi-stage loaders. Anyhow, using losetup:

The -o flag attaches at an offset in the file. Now we can treat the image like a device. So, we build an ext2 filesystem on it:

Notice that we are using root privilege (via sudo -- but you can do whatever floats your boat) for these operations. This seems necessary. We are next going to mount the device, copy over some necessary files for grub, then use the grub shell to configure the disk image for grub booting.

The --no-floppy parameter tells the grub shell not to probe the floppy disk. The (hd0) notation is grub nomenclature for disk identification. I doubt the root (hd0,0) is necessary in this context, but I haven't tried it without. Notice, too, that I use a relative mount directory, mnt/, but you can of course mount wherever your fancy is most tickled.

Now that we've added grub, we need only add the kernel image and unmount:

I wrote the image to the root of the disk image filesystem. The last step before starting bochs is to edit the .bochsrc and add the image. If you don't have a ~/.bochsrc, you'll probably want to copy one from your build source for bochs:

I didn't modify anything from the default, except that I added the line from our bochs image build in the section for ata:

Substitute a sensible path for /path/to/your/. You may also want to change the boot order, removing the floppy. Now you're ready to start bochs and execute your image:

Something went wrong with the disk image, or your kernel image is wrong, if bochs can't find or won't load the kernel with the kernel directive. Otherwise, you should be good to go!

After a while, you'll tire of typing the same grub directive every time you test, so you'll want to create a grub menu.lst. Here is a minimalist menu, which you may place as /boot/grub/menu.lst on your image: