[CentOS] RHEL/CentOS 7 Dual boot with CentOS 5.x/6.x - default boot quick solution/howto

Sat Mar 22 17:46:49 UTC 2014
Ljubomir Ljubojevic <centos at plnet.rs>

I have RHEL 7 Beta installed in dual boot with CentOS 6.x. Since RHEL 7 
installed GRUB2, I had problem that RHEL 7 is default boot.

My personal solution was to go to /etc/grub.d and run command:
mv 10_linux 31_linux

grub2-mkconfig -o /boot/grub2/grub.cfg


- /etc/grub.d is where grub2 writes down config files used to create 
boot menu.
- OS-prober creates 30_os-prober file in /etc/grub.d
- 10_linux is created for RHEL/CentOS 7.x system installed.

If you change order of files in /etc/grub.d (numbers at the start of the 
files) the list generated with grub2-mkconfig will change order in the 
GRUB2 menu :)

Fedora/RHEL 7.x have a changed GRUB2 so for further reading read:

5.3 Multi-boot manual config:


Fedora GRUB Wiki:

Ljubomir Ljubojevic
(Love is in the Air)
PL Computers
Serbia, Europe

StarOS, Mikrotik and CentOS/RHEL/Linux consultant