Do the following to keep just the last 2 kernels on your system, to keep /boot clean
1 - Edit /etc/yum.conf and set the following parameter
installonly_limit=2
This will make your package manager keep just the 2 last 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
Done. This will erase in a good fashion the old kernels, and, keep just the last 2 of them for the next upgrades.
