Rolling back the Linux kernel can save the day when a bad update breaks your system. It should be done carefully, with backups and verification. Use it to regain a stable state, then address the root ...
I'm running Centos 6.9 on a VPS and did a yum update the other day. I noticed that it removed the 2.6 kernel and installed version 4.9 from the "centos-virt-xen" repo. I'm do not recall adding this ...