升级内核

# rpm -Uvh http://www.elrepo.org/elrepo-release-7.0-3.el7.elrepo.noarch.rpm
# yum --enablerepo=elrepo-kernel install -y kernel-lt
# cat /boot/grub2/grub.cfg |grep menuentry
# grub2-set-default "CentOS Linux (4.4.221-1.el7.elrepo.x86_64) 7 (Core)"
# grub2-editenv list
# reboot
# uname -r