参考：https://www.cnblogs.com/jackron/p/13976242.html

           https://www.cnblogs.com/kate7/p/13372624.html 

1、更改yum源

# cat /etc/redhat-release
# cd /etc/yum.repos.d

vi CentOS-Linux-AppStream.repo
设置baseurl如下：
baseurl=https://mirrors.aliyun.com/centos/$releasever/AppStream/$basearch/os/

vi CentOS-Linux-Base.repo
设置baseurl如下：
baseurl=https://mirrors.aliyun.com/centos/$releasever/BaseOS/$basearch/os/

 vi CentOS-Linux-Extras.repo

设置baseurl如下： baseurl=https://mirrors.aliyun.com/centos/$releasever/extras/$basearch/os/

2、更改epel源

分别修改目录“/etc/yum.repos.d/”下的如下几个文件

epel.repo
epel-playground.repo
epel-testing.repo
epel-testing-modular.rep
epel-modular.rep

下面以epel.repo为例，其他都是一样的，把metalink注释掉，baseurl换成阿里云的，vi /etc/yum.repos.d/epel.repo

[epel]
name=Extra Packages for Enterprise Linux $releasever - $basearch
baseurl=https://mirrors.aliyun.com/epel/$releasever/Everything/$basearch
#metalink=https://mirrors.fedoraproject.org/metalink?repo=epel-$releasever&arch=$basearch&infra=$infra&content=$contentdir
enabled=1
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-EPEL-8

[epel-debuginfo]
name=Extra Packages for Enterprise Linux $releasever - $basearch - Debug
baseurl=https://mirrors.aliyun.com/epel/$releasever/Everything/$basearch/debug
#metalink=https://mirrors.fedoraproject.org/metalink?repo=epel-debug-$releasever&arch=$basearch&infra=$infra&content=$contentdir
enabled=0
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-EPEL-8
gpgcheck=1

[epel-source]
name=Extra Packages for Enterprise Linux $releasever - $basearch - Source
baseurl=https://mirrors.aliyun.com/epel/$releasever/Everything/SRPMS
#metalink=https://mirrors.fedoraproject.org/metalink?repo=epel-source-$releasever&arch=$basearch&infra=$infra&content=$contentdir
enabled=0
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-EPEL-8
gpgcheck=1

修改把这些网址修改之后，再运行： dnf repolist epel -v

3、经过1和2两步后，执行以下命令：

# dnf -y install epel-release

# dnf clean all

# dnf makecache

# dnf repolist