Dual Boot With 2 Drives

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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

6 thoughts on - Dual Boot With 2 Drives

  • Make backups of the data you care about. Also back up your MBR.

    I can’t resist. http://lmgtfy.com/?q=linux+backup+mbr

    Entire MBR is in the first 512 bytes. Bootloader is in the first 446 bytes (followed by the partition table of 66
    bytes, which is the difference of 512 and 446).

    https://wiki.archlinux.org/index.php/Master_Boot_Record#Backup_and_restoration http://www.cyberciti.biz/tips/linux-how-to-backup-hard-disk-partition-table-mbr.html http://www.linuxjournal.com/magazine/hack-and-when-disaster-strikes-restoring-master-boot-record

  • 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 http://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

  • 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.


  • I’v been trying to dual boot windows 7 and CentOS 7 for a week now without any luck.

    CentOS 5/6 and Fedora 20 recognise the Windows installation and place an entry for it on the boot menu.

    CentOS 7 anaconda recognises the Windows 7 ntfs partition at installation time as unknown but doesn’t place an entry for it in the grub2 boot files. Did you install CentOS 7 last.


  • 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