Configuring already installed Grub for Fedora?

ReddiePenguin · #1 2009-02-22, 10:00 PM CST

I have a laptop that originally came with Windows Vista.

Though I shrunk the partition and installed Ubuntu.

Though, since there is still a fair amount of disk space left on the 160GB drive, I decided to give 20GB to the root partition of Fedora while I play with Fedora.

Now, I figured it would completely mess things up if I allowed Fedora to install GRUB, because it would probably completely FUBAR Ubuntu because it didn't see to recognize Ubuntu when it was asking to install the bootloader.

I was wondering since Fedora is installed just not accessible, should I just add Fedora to the GRUB that was installed by Ubuntu?

I don't care if I have to mess with command line or anything like that, I'm used to it. I've already compiled my own packages and installed the Distro all my friends claim is hard as heck, Gentoo.

Though, I have never had a situation like this, so I want to ask before I FUBAR my laptop setup.

**stoat** · #2 2009-02-23, 04:01 PM CST

Quote:

Originally Posted by ReddiePenguin

Now, I figured it would completely mess things up if I allowed Fedora to install GRUB, because it would probably completely FUBAR Ubuntu because it didn't see to recognize Ubuntu when it was asking to install the bootloader.

I was wondering since Fedora is installed just not accessible, should I just add Fedora to the GRUB that was installed by Ubuntu?

Hello ReddiePenguin,

If that means that you chose not to install Fedora's GRUB at all, then no GRUB stages or grub.conf file were created for Fedora. But you can still boot the Fedora kernel and initial ramdisk directly from the Ubuntu menu.

Boot Ubuntu and open a terminal.
Mount the Fedora partition.
Open Fedora's grub.conf file with a text editor.
Copy the title, root, kernel, and initrd command lines for the latest Fedora kernel.
Paste those lines in the Ubuntu menu.lst file.
Repeat every time the Fedora kernel is updated.

Actually, some people prefer directly booting another system's kernel that way because it avoids the delay of going through the second system's menu. Another way to install Fedora without it disturbing an existing boot loader arrangement is to choose the boot loader option to install Fedora's boot loader in the first sector of the boot partition. At first Fedora will not boot, but it will when it is added to another system's boot menu. This method allows for some additional booting methods (e.g., configfile, chainloader) because GRUB stages and the grub.conf file are created.

ReddiePenguin · #3 2009-02-25, 02:34 PM CST

Quote:

Originally Posted by stoat

Hello ReddiePenguin,

If that means that you chose not to install Fedora's GRUB at all, then no GRUB stages or grub.conf file were created for Fedora. But you can still boot the Fedora kernel and initial ramdisk directly from the Ubuntu menu.

Boot Ubuntu and open a terminal.
Mount the Fedora partition.
Open Fedora's grub.conf file with a text editor.
Copy the title, root, kernel, and initrd command lines for the latest Fedora kernel.
Paste those lines in the Ubuntu menu.lst file.
Repeat every time the Fedora kernel is updated.

Actually, some people prefer directly booting another system's kernel that way because it avoids the delay of going through the second system's menu. Another way to install Fedora without it disturbing an existing boot loader arrangement is to choose the boot loader option to install Fedora's boot loader in the first sector of the boot partition. At first Fedora will not boot, but it will when it is added to another system's boot menu. This method allows for some additional booting methods (e.g., configfile, chainloader) because GRUB stages and the grub.conf file are created.

I like the first sector id, but one small problem left for me, how do you tell Ubuntu's Bootloader on the MBR to go to Fedora's boot menu, so far I just have Ubuntu and Vista in it's menu.

**stoat** · #4 2009-02-25, 03:52 PM CST

Quote:

Originally Posted by ReddiePenguin

how do you tell Ubuntu's Bootloader on the MBR to go to Fedora's boot menu, so far I just have Ubuntu and Vista in it's menu.

Ubuntu's boot loader in the master boot record will continue to do what it always had been doing: load and execute subsequent Ubuntu GRUB stages that eventually lead to the Ubuntu menu being shown. It's the Ubuntu GRUB menu that is being adjusted in your situation. I know of three ways to launch Fedora from the Ubuntu menu...

The direct method. It works by directly loading and executing the Fedora kernel and initial ramdisk just like Ubuntu starts its own kernel. Good for when Fedora's GRUB was not installed meaning there are no GRUB stages or grub.conf for the Fedora system. Also good for faster booting because it skips the delay of the Fedora splashscreen and/or menu and/or countdown. Bad when Fedora's kernel gets updated because it breaks and requires editing. Bad if there is no Fedora grub.conf because the kernel and initrd menu command lines then have to be hand-written from scratch (not so easy to do sometimes). To force Anaconda to create a grub.conf when Fedora is installed, choose the GRUB boot loader option to install the boot loader in the first sector of the boot partition. That will not harm the existing boot loader arrangement, but it ensures that a grub.conf is created for Fedora which allows simple copying of the menu entries from the grub.conf to Ubuntu's menu.lst (easier by far). Example (just typical) of what goes in the Ubuntu menu.lst...
Code:
```
title Fedora (2.6.27.12-170.2.5.fc10.i686)
root (hd1,4)
kernel /boot/vmlinuz-2.6.27.12-170.2.5.fc10.i686 ro root=/dev/sdb5 rhgb quiet vga=0x318
initrd /boot/initrd-2.6.27.12-170.2.5.fc10.i686.img
```
The configfile command. It works by reloading the GRUB menu with Fedora's grub.conf information. Requires the Fedora GRUB boot loader be installed in the first sector of the boot partition in order to force Anaconda to create a grub.conf for Fedora. Good because it is "immune" to breakage by Fedora kernel updates. Example (just typical) of what goes in the Ubuntu menu.lst...
Code:
```
title Fedora
configfile (hd1,4)/grub/grub.conf
```
If Fedora does not have a separate boot partition, then do it like this...
Code:
```
title Fedora
configfile (hd1,4)/boot/grub/grub.conf
```
The chainloader command. It works by loading and executing the boot sector code of the Fedora partition. Therefore this method requires that Fedora's GRUB boot loader be installed in the first sector of the boot partition during installation. Good because it is "immune" to breakage by Fedora kernel updates. Example (just typical) of what goes in the Ubuntu menu.lst...
Code:
```
title Fedora
chainloader (hd1,4)+1
```

P.S.: How to install Fedora's GRUB boot loader in the first sector of the boot partition.

ReddiePenguin · #5 2009-02-26, 10:38 AM CST

Thank You, so much for your elaborate and detailed answer.

That was way more than I asked for, but definitely glad I got all of that. It really helps me better understand boot loaders, which always were somewhat hazy for me.