LINUX: Grubby Command To Change Default Bootup Kernel on Linux Host Operating System (OS)

Below grubby command can be used.

grubby --set-default /boot/vmlinuz-<kernel version>

You can choose the kernel version vmlinuz-<kernel version> file from /boot in above command which you want to set as default bootup kernel. For e.g. if you want to set 4.1.12-124.75.3.el7uek.x86_64 as default kernel, check for /boot/vmlinuz-4.1.12-124.75.3.el7uek.x86_64 file, and then run below command.

grubby --set-default /boot/vmlinuz-4.1.12-124.75.3.el7uek.x86_64