Creating a Grub CD

Note: Impatient natures can skip the first 3 paragraphs.

Did it ever happen to you that you installed an additional operating system on your computer only to find the old one is „gone“? It sure happened to me. To elaborate a bit, by „gone“ I actually mean that the boot configuration of the OS was overwritten with the one of another OS. Strictly speaking overwritten is the wrong term, as aside from the MBR things get seldom overwritten, so maybe I should say replaced. In some cases things go fine and the old OS will be integrated in the new boot selection screen. Though sometimes things go wrong and this is where my findings might come in handy.

So ok, the other day I wanted to install Windows 7 on my notebook. Note that like 2 years ago I set up the system in a special way that suited my needs. I had Windows Vista (booted it like twice a year – haha in retrospect), Windows XP (my main OS) and Ubuntu Linux (whenever I needed Linux) installed and neatly organized via Grub. Each selection in Grub directly booted the respective OS, no additional selection screen was displayed from the Windows OS loader (bootmgr for Vista and ntldr for XP). If I hadn't set it up that way, it would just display „Microsoft Windows“ and after selecting this option I'd be presented a nested selection menu for Vista and XP. Needless to say this is not what I wanted, that's why I went through all the hassle of setting it up this way.

At this time I wanted to do a little bit more with Vista tough through some obscure error I couldn't install the Service Pack 2. This and the availability of Windows 7 made me thinking about replacing it in the first place. However, I remembered the chores to get a clean setup with the boot configuration so I wanted to prepare for the worst.

Enter a bootable CD containing grub with my specific configuration. Including the machine-specific (or should I say hard drive in the age of virtual machines) configuration is a bonus for convenience as grub comes with a command line so a generic CD would be enough for emergency purposes. I'm sure there is a hundred different ways to create a grub CD (not really but surely quite some). I chose a most probably not very elegant solution but it worked and it was basically stuff I was already experienced with since I created a lot of bootable BIOS-Update CDs based on DOS floppy images (reminds me I should probably blog about that as well). For a pure Grub CD you should probably look here.

Basically I took a DOS grub floppy from here, modified it as it suited me and then burned it to a CD-RW with bootable floppy disk emulation using Nero Burning ROM - though any other software capable of burning bootable CDs with floppy emulation might be ok. I removed the lots of selection screens from the grub floppy and put my menu.lst file on it. For this task I used the fancy tool WinImage. Linux users should probably read the info on the website of the grub floppy to get instructions on how to create such a disk. The grub floppy I linked has a lot of fancy features that might come in handy for one or another, but for me a basic grub disk was all I needed. Basically I removed all files except for the stage1 and stage2 files in /boot/grub and then put my own menu.lst in this directory. I took it directly from the /boot/grub folder from my Linux system. However you can also write a configuration from scratch, though that is outside of the scope of this blog.

Next step would be testing if it actually works. I recommend adding a dummy entry to either the CD or local grub configuration or changing the title or whatever you like in order to distinguish your local grub from the one on CD. Then you can reboot your computer, try booting from CD and if everything went fine you should be able to boot any of your operating systems from it.

Now that you have your backed up boot configuration you can start messing with other operating systems, especially the ones which like to replace MBRs and the likes. Remember that Windows-based OSes need their respective bootloader in order to be started, though most installation procedures don't remove those. If they do, you will still have the new operating system which can be used to put one in place, assuming the installation went fine.