[CentOS] Dual boot with 2 drives

[Joseph Hesse]

On 08/09/2014 05:23 AM, Alan McRae wrote:
> No problems Joe. I have done this multiple times.
>
> I assume you have Fedora 20 on sda (the first disk) with
> the bootloader (grub2) on sda. Your BIOS will be set to boot sda.
>
> You install CentOS 7 on sdb (obvious).
>
> Your options are with the bootloader (grub2). If you install
> the bootloader on sdb the two systems will remain separate.
> You will have to change the BIOS to boot either sda (F20)  or sdb (C7).
>
> The way I prefer would be to install the new bootloader on sda
> (overwriting the current configuration).
> Your BIOS will still boot sda which will take you into
> the grub2 menus which will show both Fedora 20 and CentOS 7.
>
> You need to be aware that in the above configuration sda will
> boot into /boot on sdb (C7) which will have the dual boot menus.
> Don't wreck this directory or you won't be able to boot F20 (easily).
>
> The F20 and C7 installers are very good. They scan the disks for
> linux and Windows installations and add them into the boot menu for you.
>
> I have a laptop which boots C7, C6, F20, XP and 3 versions of Android
> using grub2.
>
> Alan
>
Alan,

Thank you for your reply.

I was concerned that if, during the C7 install, I put the bootloader on 
sda that it would wipe out what was already there and prevent me from 
booting F20.  Apparently this is not the case.

However, I decided to put the bootloader on sdb so I could easily wipe 
out the C7 install and use the drive for something else.

I did the install from the C7 DVD disk.  Maybe I missed something but 
once I indicated I only wanted to use the sdb disk (checkmark on icon), 
I did not have the option as to where to put the bootloader.

After the install, when I boot the computer I go directly to F20. If I 
press the ESC key when booting I get a BIOS bootloader menu. 
Miraculously, sdb is on the list.  Apparently the BIOS is smart enough 
to recognize that sdb is bootable and, therefore, puts it on the list.

Thanks,
Joe