This is quick guide howto delete/remove/clean old kernels on Fedora, CentOS, Red Hat (RHEL). I use here two kernel as example, if you want to keep other more or less, then adjust amount of installed kernels as you wish. Normally reason why you maybe want remove kernels is limited disk space, example on VPS servers and laptop. This is very easy task, you need yum-utils package.

rpm -q kernel
kernel-2.6.32-279.el6.x86_64
kernel-2.6.32-279.2.1.el6.x86_64
kernel-2.6.32-279.5.2.el6.x86_64
kernel-2.6.32-279.9.1.el6.x86_64

Install yum-utils on Fedora 23/22

dnf install yum-utils

Fedora 21/20/19/18/17/16, CentOS, Red Hat (RHEL)

yum install yum-utils

Package-cleanup set count as how many old kernels you want left

package-cleanup --oldkernels --count=2

Edit /etc/yum.conf or /etc/dnf/dnf.conf and set installonly_limit:

installonly_limit=2