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 On 09/08/2014 17:02, Ted Miller wrote: > On 07/31/2014 11:37 AM, Joseph Hesse wrote: >> Hi, >> >> I have a laptop with 2 hard drives. The first has Fedora 20 (no windows >> or anything else) and the second is unused. I would like to install >> CentOS7 on the unused drive so I can dual boot with the choice of the 2 >> OS's on the Grub menu. >> I am comfortable in partitioning drives and installing Linux >> distributions. I am afraid I may mess up the MBR and/or set up Grub >> incorrectly so I lose everything. >> >> Please point me to some documentation to help me. >> >> Thank you, >> Joe > I see no answers to this, so I will tell you this: If you have a CD (or USB > drive) with the Super Grub Disk from www.supergrubdisk.org, you will be > able to get to your linux installations no matter how badly you mess up you > MBR. It is usually quite difficult to cut yourself off from an existing > installation, because usually the new install process will find the old > installation and include it on the new menu. > > Ted Miller > > > _______________________________________________ > CentOS mailing list > CentOS at centos.org > http://lists.centos.org/mailman/listinfo/centos