Dual Booting CentOS 6 & Fedora 15
 

I'm not exactly a 'newbie', but I do have a question that I'm not quite clear on. I have Fedora 15 (KDE) installed on a box, and I want to dual boot CentOS 6 with it. Here's my set-up:

sda-mbr (Windows bootloader)
sda-1 (WINXP RECOVERY)
sda-2 (WINXP)
sda-3 (Fedora 15)

sdb-mbr (Fedora GRUB)
sdb-1 (Windows 7)
sdb-2 (SWAP)
sdb-3 (CentOS)

Should I install the CentOS bootloader in the first sector of sdb3? If I do this I think that I'll have to boot Fedora, mount sdb3 and take the GRUB information for CentOS (with UUID, kernel, initrd) to add to my Fedora's /boot/grub/grub.conf and /boot/grub/menu.lst. Is this right? I use sda to boot Windows and sdb to boot Linux.

Yes. What you plan in your last paragraph is what will need to be done. The file to edit should be the grub.conf as I believe in Fedora the menu.lst is just a link to grub.conf. If you copy the entry from CentOS to the Fedora grub.conf and it doesn't boot, try just chainloading it.

Which of your OS's did you install first? CentOS or Fedora?
You might want (if you have the disk space to spare) to move the malware collection (on sdb1) to sda3 and then move Fedora to sdb1. Then using the Fedora LiveCD restore the Fedora bootloader to the mbr of sdb and you'll get both OS's (Fedora and CentOS) in the menu.

Personally I would chainload regardless. That way if something (kernel name, UUID whatever) changes, things don't break.

Well I was correct. I installed the bootloader to the first sector of sdb3, booted Fedora, mounted sdb3 and copied the kernel/initrd/grub information from the CentOS /boot/grub/grub.conf to Fedora's /boot/grub/grub.conf. I can boot either Fedora or CentOS from the Fedora grub screen. Now I'm curious about chainloading, what is it and how do you utilize chainloading? I can post my Fedora grub.conf information if its needed.

Can anyone explain this for me?

Basically, the way you are booting CentOS from Fedora, Grub is pointed to the kernel and initrd files. If you chainload, it looks for the boot file/menu and would go to the grub.conf file of CentOS and from there boot the kernel. The boot files go to the same location on a partition so this should work for any OS.

Thank you all so much for the information.