I'm very new to Linux. I have been using Windows/Mac during my whole life, but now I have decided to use Linux. So I'm trying to configure a dual boot system with Windows 10 and CentOS 7. I already have installed both of these OSs: CentOS 7 on one partition of the HDD and Windows 10 on the SSD (which is not partitioned). I found a great tutorial on how to edit /boot/grub2/grub.cfg. The author edits the grub.cfg file, adding these lines:

menuentry "Windows #" {
  set root='(hd0, 0)'
  chainloader + 1

hd0,0 does not work for booting Windows (which I have installed on my SSD). At boot I have "Windows 10" in the menu, but it isn't working.

Edit: I have already reinstalled both OS in UEFI and now it works.

  • what do you mean with Windows 10 on SSD (no partition)? and are you using EFI? – Jannis Aug 29 '15 at 18:03
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    I mean there are 2 physical disks. SSD and HDD. HDD I have partitioned and SSD not. I don't know what EFI does mean. I have used lsblk command and HDD have sda1 and sda2 and SSD have only sdb1. – Cyberikia Aug 29 '15 at 18:36
  • ok then Windows automatically partitioned your ssd (sdb1 is this automatically created partition). EFI is the successor of BIOS, if your mainboard is not older than 2 years, you can be quite sure that you have such a mainboard. – Jannis Aug 30 '15 at 10:29
  • I think this it is BIOS. I run [ -d /sys/firmware/efi ] && echo UEFI || echo BIOS and the echo is BIOS. However when appears my mother boards splash-screen it says press DEL or F2 to access UEFI BIOS setup. Also now I can't boot Windows, even if I choose my SSD from boot menu. – Cyberikia Aug 30 '15 at 15:25
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    If your windows disk is sdb1 then I think the root line for the Windows menuentry in grub.cfg should be: set root='(hd1, 0)' i.e. sda=hd0,sdb=hd1 (and ',0' indicates partition 1). It's worth a try anyway. – gogoud Sep 9 '15 at 9:19

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