How to change default kernel in rhel 7

Step 1 

check the running kernel version

uname -a

Step 2 

List the kernel 

awk -F\' '$1=="menuentry " {print $2}' /etc/grub2.cfg

Step 3 

set the kernel that you want to put it default with following command

grub2-set-default 2

Step 4

Changes to /etc/default/grub require rebuilding the grub.cfg file as follows

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

reboot and check