How to check the list of installed kernels and the current one
Get list of installed kernels on CentOS
$> rpm -qa kernel kernel-2.6.32-696.13.2.el6.x86_64 kernel-2.6.32-696.el6.x86_64 kernel-4.9.75-30.el6.x86_64 kernel-2.6.32-696.16.1.el6.x86_64
Get current kernel
$> uname -r 4.9.75-30.el6.x86_64
Downgrade to a previous one
You don't need to downgrade or uninstall a kernel, you just modify the boot loader to load a previously one installed.
Change default=0 to default=1
Reboot and hope for the best !
It is not over.. your build might still pickup the wrong kernel headers. In my case I had to remove them.
Remove unneeded kernel headers
$> yum list installed | grep kernel
... find which ones to remove
$> sudo yum remove kernel-devel-4.9.75-30.el6.x86_64 $> sudo yum remove kernel-headers-4.9.63-29.el6.x86_64