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

[Ljubomir Ljubojevic]

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

Explanation:


- /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:
http://www.gnu.org/software/grub/manual/grub.html#Multi_002dboot-manual-config


and

Fedora GRUB Wiki:
http://fedoraproject.org/wiki/GRUB_2


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

StarOS, Mikrotik and CentOS/RHEL/Linux consultant