How to roll back to a patched server to an earlier patch level

1.) Edit the /etc/grub.conf file to make the kernel boot to an eariler kernel. Inside of /etc/grub.conf, file the line “default=0” and change to “default=1”

#vi /etc/grub.conf

Change: default=0
To: default=1
<save and quit>
2.) Reboot the server so you can boot into the second, pervious, kernel

#reboot
3.) After reboot, find out when the patching took place.

#yum history list

4.) After finding out when the patching took place. undo the patching by the ID number.

#yum history undo <ID # of patch update>

5.) Check for patch duplicates

#yum check duplicates