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Monday, June 6th, 2005

Editing GRUB

I mentioned a while ago that when I installed SuSE 9.3 on my home computer, it ignored the Fedora Core 3 that was already installed when configuring the GRUB bootloader. I tried a wild guess as to how to add FC3 and, as it turns out, I was way off.

This weekend I sat down to readdress the problem. I did some research online to try and determine how to edit GRUB, and in doing so, learned something about how it works. Although GRUB resides in the MBR, it fetches a configuration file from the very small boot partition that is a part of every linux install.

So I decided to take a look at the configuration under SuSE. Since SuSE was the last OS installed, its version of GRUB was the one I was currently dealing with. (The green splash screen with the gecko are a strong reminder every time I boot the computer.) So I started SuSE and used the file manager in superuser mode to navigate to the /boot/grub/grub.conf file. In this file I found the boot commands for each OS, including the wrong ones for FC3. Fair enough – I just have to figure out what to put in there for FC3. But wait!, I thought – I don’t have to figure it out – I just have to navigate to Fedora’s grub.conf file and copy it to here!

So I looked to see if SuSE had noted the FC3 partitions and mounted them. It didn’t look like it in the /mnt directory, but I checked /etc/fstab to be sure. No mounting instructions there. Curious – I would have though that SuSE would have noticed and mounted two other ext3-formatted partitions.

It is a sad commentary on my linux skills that at this point, I chickened out on mounting the other partitions myself and opted to reboot Windows and use Windows Explorer to find and open the grub.conf file in the Fedora boot partition. I have one of the many utilities that allows me to mount ext3 partitions in Explorer. There I found the exact boot commands that GRUB under FC3 had used – and it’s a good thing I found them, because I never would have guessed, and I needed to know the exact version of the kernel that I had last upgraded to.

Rebooting, I paused GRUB and hand entered the commands. It worked – there was good old FC3! So I added them to the configuration file in SuSE and everything is now peachy.

Except, of course, for the reason that I needed to get into FC3 all of a sudden – my Windows was not detecting my wireless access point, which meant no Internet. Sadly, Fedora couldn’t connect either. But I was able to see other access points with my card’s utility, and I was able to connect using the laptop out in the living room. But that’s a problem for another day.

Posted by Greg as OS at 09:19 PST

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