However, when I tried the steps below I realised that grub had not been installed correctly and it dropped my into the grub rescue environment from which I did not seem to be able to fix the problem. Details on how I did fix it below.
First of all, details on how to use the image with KVM. The following steps can be done in graphical management utilities but it is just as easy from the commandline using virtinstall.
Run virtinstall and tell it to import rather than to run an installer, I gave the VM a basic set of requirements namely just 2GB of RAM.
virt-install --name LFS --ram 2048 --disk <location of image file> --import
This created my VM configuration and started the VM (if it had been working correctly the OS would have started) and launched virt-viewer so I could see the console.
As noted earlier this failed to boot first time and dropped me into the grub rescue prompt, therefore I had to find a different way to get grub installed onto the MBR of my disk image.
Lots of posts on forums talk about mounting the disk using losetup, this is fine for raw images but I was using qcow2 format and had made it available via NBD. Other posts talk about installing the grub version from the host system onto the disk image, this would have worked, however why go to the effort of building a custom system if you are going to just copy files from the host system.
Whatever I tried inside a chroot onto my filesystem failed to work (even though grub-install returned success), so I looked for a way to run the grub utilities from the filesystem in my disk image by directly from my host system.
Fortunately it seems that grub-install is setup for running in just this manner with a number of optional arguments to override directory paths and locations of utilities. With my diskimage made available with qemu-nbd and mounted under /media/LFS I used the following command to install grub to the MBR of my disk image.
/media/LFS/usr/sbin/grub-install --boot-directory=/media/LFS/boot/ --directory=/media/LFS/usr/lib/grub/i386-pc --modules="ext2 part_msdos" --grub-mkimage=/media/LFS/usr/bin/grub-mkimage --grub-probe=/media/LFS/usr/sbin/grub-probe --grub-mkrelpath=/media/LFS/usr/bin/grub-mkrelpath /dev/nbd0 --debug
A quick explanation of the options (for more details check grub documentation)
--boot-directory location of "/boot", where grub files will be installed
--directory location to copy boot files from
--modules which modules to load
--grub-* locations of various grub utilities
--debug undocumented (according to grub-install script) option so I can see exactly what commands it is running to make sure it does not damage grub on my host system
Now when I startup this VM under KVM it boots fine.
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| Grub screen |
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| Login prompt - before compiling kernel to include nic driver |
