rpm --import https://www.elrepo.org/RPM-GPG-KEY-elrepo.org
rpm -Uvh http://www.elrepo.org/elrepo-release-7.0-3.el7.elrepo.noarch.rpm
yum --disablerepo="*" --enablerepo="elrepo-kernel" list available
yum --enablerepo=elrepo-kernel install kernel-ml
uname -sr
reboot

参考文档https://linux.cn/article-8310-1.html

调整内核启动顺序

1，首先查看当前系统有几个内核。比如：

[root@21yunwei ~]# cat /boot/grub2/grub.cfg |grep menuentry

if [ x"${feature_menuentry_id}" = xy ]; then
menuentry_id_option="--id"
menuentry_id_option=""
export menuentry_id_option
menuentry 'CentOS Linux (3.10.0-327.22.2.el7.x86_64) 7 (Core)' --class centos --class gnu-linux --class gnu --class os --unrestricted $menuentry_id_option 'gnulinux-3.10.0-327.el7.x86_64-advanced-80b9b662-0a1d-4e84-b07b-c1bf19e72d97' {
menuentry 'CentOS Linux (3.10.0-327.el7.x86_64) 7 (Core)' --class centos --class gnu-linux --class gnu --class os --unrestricted $menuentry_id_option 'gnulinux-3.10.0-327.el7.x86_64-advanced-80b9b662-0a1d-4e84-b07b-c1bf19e72d97' {
menuentry 'CentOS Linux (0-rescue-7d26c16f128042a684ea474c9e2c240f) 7 (Core)' --class centos --class gnu-linux --class gnu --class os --unrestricted $menuentry_id_option 'gnulinux-0-rescue-7d26c16f128042a684ea474c9e2c240f-advanced-80b9b662-0a1d-4e84-b07b-c1bf19e72d97' {
　　

2，设置默认的启动内核。比如我们选择上边中的CentOS Linux (3.10.0-327.el7.x86_64) 7 (Core)这个内核为默认启动。

[root@21yunwei ~]# grub2-set-default "CentOS Linux (3.10.0-327.el7.x86_64) 7 (Core)" 配置默认内核
验证是否修改成功：

[root@21yunwei ~]# grub2-editenv list
saved_entry=CentOS Linux (3.10.0-327.el7.x86_64) 7 (Core)
　　

3，重启机器观察。
重启成功以后查看下机器的内核是不是该内核：

[root@21yunwei ~]# uname -r
3.10.0-327.el7.x86_64