On Sun, 12 Dec 2004 00:06:49 -0600, Andrew Robinson <awrobinson@xxxxxxx> wrote: > John Cox wrote: > > > > On Sat, 11 Dec 2004 10:58:56 -0600, Andrew Robinson <awrobinson@xxxxxxx> wrote: > > > >>John Cox wrote: > >> > >> > >> > >>>I have an extra partition that I use to test other distributions. My > >>>normal procedure is install but not let the new OS install grub. I > >>>then manually modify my FC3 grub.conf. I didn't do this with an > >>>installation of caos so now when I boot I'm using the grub.conf on the > >>>caos partition. I don't want this as FC3 is my main OS. I tried using > >>>FC3 rescue to reinstall grub to /dev/hda but that doesn't do the job. > >>>So what determines which grub.conf the system uses and how do I change > >>>that? > >> > >>John, this is what I've done in the past. I cannot claim it is the best > >>solution. > >> > >>Go ahead and boot into your new system. Then mount the partition with > >>the FC3. Copy the grub.conf from the FC3 partition to the current > >>/boot/grub directory. Add the new distro to that grub.conf. Reboot. You > >>should be able to pick the main FC3 entry from the grub menu. > >> > >>Doing it this way, the Master Boot Record still points to the new > >>distro. So once you are booted back into FC3, you should run > >>grub-install to get the MBR to point back to the FC3 partition. > >> > >>Now here's a way to have a fix ready in the future. However, you need to > >>do this BEFORE installing the new distro. You can install grub on a > >>diskette and have that direct your booting. My writeup is at work, so > >>these steps are from memory. I think they are basically correct. > >> > >>1. Insert a diskette into the diskette drive. > >>2. Format it: mkfs.vfat /dev/fd0. Note: you could format the diskette as > >>either ext2 or vfat. I choose vfat so that if I have to edit the > >>grub.conf on it, I can do so from either Linux or Windoze. > >>3. Mount the diskette: mount /mnt/floppy > >>4. Install grub onto the diskette: grub-install --root-directory > >>/mnt/floppy /dev/fd0 > >>5. Copy your grub.conf to the diskette: cp /boot/grub/grub.conf > >>/mnt/floppy/boot/grub > >>6. Add this entry to the grub.conf on the diskette: > >>title Local Hard Drive > >> root (hd0) > >> chainloader +1 > >>7. Make this new entry the default. This makes the default behavior of > >>the grub floppy to boot from the local hard drive. I figure this keeps > >>me from getting into too much trouble. > >>8. I like to make the timeout on the diskette long to give me time to > >>decide what I'm going to do. (Conversely, I like to make the timeout on > >>the hard drive short so I don't have to wait for the default behavior.) > >>In /mnt/floppy/boot/grub/grub.conf, set timeout=30. > >>9. "grub.conf" is a Red Hat convention. Gnu grub thinks the name of the > >>file should be "menu.lst". So make a copy: cp > >>/mnt/floppy/boot/grub/grub.conf /mnt/floppy/boot/grub/menu.lst > >>10. Test it. With the floppy inserted, reboot. > >> > >>If the grub floppy works, you should get your ususal menu with the new > >>entry I suggested adding. The grub menu will probably have a blank black > >>background. > >> > >>If the grub floppy doesn't work, eject it and reboot. You should get > >>back to your grub menu. > >> > >>When you install a new distro, this grub floppy won't know about it > >>until you add it to the floppy's grub.conf (and menu.lst). But assuming > >>you have not erased the partitions with you old distro, the floppy grub > >>should let you get back to them. > >> > >>HTH, > >> > >>Andrew Robinson > >> > > > > So then the MBR is what points to the caos installation. How is the > > MBR changed to point to a particular place? Is that what grub-install > > does? Your suggestion about how to avoid this in the future sounds > > good but I want to delete the caos partition but I am not sure if I'll > > be able to boot my FC3 OS (my main OS) once I do that. > > John > > > > John, > > The short answer to your question is yes and yes. When you run > grub-install, it puts a stage 1 loader on the MBR which points back to > the partition from which grub-install was run. I believe the > --root-directory option to grub-install changes this. > > So yes, if you delete the caos partition before fixing grub, it will > confuse grub. What I believe will happen is this. Grub will start but > not be able to find the grub.conf file. It will then drop into the grub > command mode. I see in your other post, you have at least the grub > command mode. Once in command mode, you can point grub to the > configuration file, the grub.conf, on your Fedora partition and start it. > > So that's the worse case senario. Before you delete the caos partition, > you can try this to get your old grub back: > 1. Go ahead and boot into the caos distro. > 2. Mount the Fedora partition. > 3. Copy the grub.conf from the Fedora partition to the caos partition. > 4. Reboot. You should get your old grub menu. > 5. Select the Fedora partition. Boot into it. > 6. Once in Fedora, run grub-install to get the MBR to point to the > Fedora partition. > > After this, deleting the caos partition shouldn't cause you any problems. > > Again, HTH. > > Andrew > Thank you everyone. John
