Reinstalling the Kernel in CentOS or RHEL Revision as of Monday, 21 December 2015 at 02:30 UTC

Some facts

• yum does not remove the kernel entirely.
• You can remove and reinstall the kernel since it’s entirely in
  memory

Reinstalling your kernel

To see a list of installed kernels:

 [root@server ~]# rpm -qa | grep kernel | sort
 kernel-2.6.18-308.11.1.el5
 kernel-2.6.18-308.13.1.el5
 kernel-2.6.18-308.4.1.el5
 kernel-2.6.18-308.8.1.el5
 kernel-2.6.18-308.8.2.el5
 kernel-headers-2.6.18-308.13.1.el5
 kernel-xen-2.6.18-308.11.1.el5
 kernel-xen-2.6.18-308.13.1.el5
 kernel-xen-2.6.18-308.4.1.el5
 kernel-xen-2.6.18-308.8.1.el5
 kernel-xen-2.6.18-308.8.2.el5

To remove specific ones,

 yum remove kernel-2.6.18-308.11.1.el5 kernel-2.6.18-308.13.1.el5

And so on. Now you can

 # Install the version you want 
 yum install kernel-2.6.18-308.13.1.el5
 
 # or the latest version
 yum install kernel

Check /boot/grub/menu.lst, and then reboot.