hello
when you get dedicated server from ovh with centos Os you can't install any other kernel , you can use only OVH kernel "grs" , If you need to Change OS Kernel Follow these steps :
1- open yum.conf using VI Editor :
vi /etc/yum.conf
2- find this Line :
exclude=kernel*
3- delete this line (using "dd" if you open via VI editor)
4- save file
Now try to install any other kernel or update kernel
Be careful when you are dealing with Kernel is possible to loss system