CentOS update kernel

//rpm -Uvh https://mirrors.cnnic.cn/epel/epel-release-latest-7.noarch.rpm
yum install epel-release

sed -e 's!^metalink=!#metalink=!g' \
    -e 's!^#baseurl=!baseurl=!g' \
    -e 's!//download\.fedoraproject\.org/pub!//mirrors.tuna.tsinghua.edu.cn!g' \
    -e 's!//download\.example/pub!//mirrors.tuna.tsinghua.edu.cn!g' \
    -e 's!http://mirrors!https://mirrors!g' \
    -i /etc/yum.repos.d/epel*.repo

# 对于 CentOS 7
sudo sed -e 's|^mirrorlist=|#mirrorlist=|g' \
         -e 's|^#baseurl=http://mirror.centos.org|baseurl=https://mirrors.tuna.tsinghua.edu.cn|g' \
         -i.bak \
         /etc/yum.repos.d/CentOS-*.repo

# 对于 CentOS 8
sudo sed -e 's|^mirrorlist=|#mirrorlist=|g' \
         -e 's|^#baseurl=http://mirror.centos.org/$contentdir|baseurl=https://mirrors.tuna.tsinghua.edu.cn/centos|g' \
         -i.bak \
         /etc/yum.repos.d/CentOS-*.repo

yum update
sudo rpm --import https://www.elrepo.org/RPM-GPG-KEY-elrepo.org
sudo rpm -Uvh https://www.elrepo.org/elrepo-release-7.0-3.el7.elrepo.noarch.rpm
yum list available --disablerepo='*' --enablerepo=elrepo-kernel
sudo yum --enablerepo=elrepo-kernel install kernel-ml
sudo yum --enablerepo=elrepo-kernel install kernel-lt
uname -a
awk -F\' '$1=="menuentry " {print $2}' /etc/grub2.cfg
yum install yum-utils
package-cleanup --oldkernels --count=1

/etc/yum.conf
installonly_limit=2

dnf autoremove

grub2-set-default 0
grub2-mkconfig -o /boot/grub2/grub.cfg