将CentOS7.7在线升级到CentOS8.0

yum -y install epel-release
yum -y install rpmconf yum-utils

rpmconf -a    #如果出现一些提示，输入Y和回车继续
执行
package-cleanup --leaves
package-cleanup --orphans

如果没提示继续

yum -y install dnf
dnf -y remove yum yum-metadata-parser
rm -Rf /etc/yum

dnf -y upgrade
dnf -y upgrade http://mirrors.163.com/centos/8.0.1905/BaseOS/x86_64/os/Packages/centos-release-8.0-0.1905.0.9.el8.x86_64.rpm
dnf -y upgrade https://dl.fedoraproject.org/pub/epel/epel-release-latest-8.noarch.rpm
dnf clean all

开始升级

rpm -e `rpm -q kernel`
rpm -e --nodeps sysvinit-tools
dnf -y --releasever=8 --allowerasing --setopt=deltarpm=false distro-sync

提示出错拆卸掉冲突软件

rpm -e --nodeps kernel-ml
rpm -e --nodeps redhat-rpm-config
wget http://mirror.centos.org/centos/8/AppStream/x86_64/os/Packages/redhat-rpm-config-116-1.el8.0.1.noarch.rpm
rpm -ivh redhat-rpm-config-116-1.el8.0.1.noarch.rpm --force --nodeps
rpm -e --nodeps bash-completion
rpm -e --nodeps pycairo
rpmconf -a

安装CentOS8组件

dnf -y install kernel-core
dnf -y groupupdate "Core" "Minimal Install"
cat /etc/redhat-release
reboot

如果dnf update错误,拆卸epel7

dnf remove epel-release
dnf install https://dl.fedoraproject.org/pub/epel/epel-release-latest-8.noarch.rpm -y