Every linux system has /boot partition and which can be full after doing kernel updates or system updates which may cause issue in the system if it gets full, you will not been able to update or upgrade your os or other packages. follow the steps below which will keep last 2 kernels on system and keep /boot partition clean.
1 – Edit /etc/yum.conf and set the following parameter
This will make your package manager keep only last 2 kernels on your system including the one that is running.
2 – Install yum-utils:
yum install yum-utils
3- Make an oldkernel cleanup:
package-cleanup –oldkernels –count=2
This will erase in a good fashion and keep only last 2 of them for the next upgrades and your /boot partition will get free space.