How to change default Kernel in CentOS 7

In Centos and RHEL 7 systems, the GRUB2 is the most common and default boot loader and grub2-mkconfig utility can use to make any changes in grub configuration.
Run the following command to boot the system with specify/old kernel:

[root@linuxcnf ~]# grub2-set-default 1

Run the following command to rebuild grub configuration:

[root@linuxcnf ~]# grub2-mkconfig -o /boot/grub2/grub.cfg

Run the following command to reboot the system with old kernel!!!

[root@linuxcnf ~]# reboot

Finally, run the below command to verify the changes:

[root@linuxcnf ~]# uname -sr Linux 3.10.0-862.9.1.el7.x86_64 [root@linuxcnf ~]#

Done!!! Now the system is running on old kernel.