1、Make sure your package repositories and installed packages are up to date by issuing the following command:
yum update
2、结束后看下当前的核心是啥：
uname -a
现在（我发帖日）的默认是：4.8.6-x86_64-linode78
3、Issue the following command to install the default kernel for CentOS6:
32-bit CentOS: : yum install kernel-PAE.i686 64-bit CentOS: : yum install kernel.x86_64
4、Create a file named /boot/grub/menu.lst with the following contents. Adjust the title, kernel, and initrd lines to reflect the actual file names found in the /boot/ directory.
- /boot/grub/menu.lst
timeout 5 title CentOS (2.6.32-431.23.3.el6.x86_64) root (hd0) kernel /boot/vmlinuz-2.6.32-431.23.3.el6.x86_64 root=/dev/xvda initrd /boot/initramfs-2.6.32-431.23.3.el6.x86_64.img
然后，把里面 2.6.32-431.23.3.el6.x86_64 对应的全部替换为 /boot 目录下最新的对应的一批文件名。
timeout 5 title CentOS (3.10.0-514.2.2.el7.x86_64) root (hd0) kernel /boot/vmlinuz-3.10.0-514.2.2.el7.x86_64 root=/dev/sda initrd /boot/initramfs-3.10.0-514.2.2.el7.x86_64.img
5、修改 linode 的Configuration Profile， 将核心改为 GRUB
6、重启后 查看 uname -a ， 核心已变。 o ye
参考：https://www.linode.com/docs/tools-reference/custom-kernels-distros/run-a-distributionsupplied-kernel-with-pvgrub/