I offer this "Answer" as a supportive post AND as additional information on a point.
The Andreas Reiff answer with 4-step details worked very well for my situation and I learned/found an interesting "oh, by the way".
My situation was an attempt to TRIPLE-BOOT CentOS 7, Windows Server 2012, and Windows7.
I thought I would be smart and add two separate Windows
menuentry items, one for WinServer2012 and one for Win7.
I knew each partition number and found UUID for each Windows-related partition/installation, and gave it my best shot for both to appear in the GRUB menu. Both Windows entries did appear, but one failed with a message informing me of a missing boot manager or something like that. I did notice the entry that failed did not have the asterisk in the 'Boot' column.
Device Boot Start End Blocks Id System
/dev/sda1 2048 419432447 209715200 83 Linux
/dev/sda2 419432448 450889727 15728640 82 Linux swap / Solaris
/dev/sda3 * 450889728 765462527 157286400 7 HPFS/NTFS/exFAT
/dev/sda4 765462528 976773119 105655296 7 HPFS/NTFS/exFAT
However, the one Windows entry that did work (with '*' in the Boot column) took me to what is surely the normal WINDOWS boot manager that presented both of my Windows installations there...and each installation of Windows did successfully boot.
Aside from a different value for the UUID line, my only difference was the
set root='(hd0, 3)' line that included the associated partition number.
What I ended up doing was to have
- one GRUB
menuentry for my CentOS 7
- another single GRUB
menuentry for 'anything Windows' which covered my multiple (both) Windows installations...by way of the single, boot-able NTFS entry at
Both Windows installations got covered by a single GRUB
HOWEVER, each of the two Windows installations appeared as separate entries in the Windows boot manager...after I picked the 'anything Windows' entry from the initial GRUB menu.
I agree that running
grub2-mkconfig was probably not needed. It seems to have worked without it, in my experiment.
This got the job done for me. The answer from Andreas helped me achieve what I wanted and I learned something I thought I should share, as well. And a THANK-YOU to Andreas.