I have 3 OS's on my computer.
First, I installed windows 10.
Secondly, Ubuntu 16.04 LTS (with GUI).
Thirdly, CentOS 7 (without GUI).
During Ubuntu installation, I installed Grub2 into MBR and it was taking care of booting.
Then, during CentOS installation I again installed Grub2 into MBR, so that CentOS controls booting. And it was controlling for a year or so.
However, recently, I've used such commands as apt-update and apt-upgrade while on Ubuntu system, and now the boot process is controlled by Ubuntu. How do I know ? Well, when the booting process starts and I get to choose which OS I want to load, the background of the menu is in Ubuntu colors. Previously, when CentOS installation based Grub2 was in control of booting everything was in black and white.
How do I make CentOS Grub2 be responsible for the booting process again ?
I've tried to login to CentOS and do something like :
grub2-mkconfig -o /boot/grub2/grub.cfg
But this didn't do anything.