新服务器，出现以下报错：
[root@00021 ~]# yum install -y wget && wget -O install.sh http://xxxxx/install.sh && sh install.sh
^CCentOS-8 - AppStream 0.0 B/s | 0 B 00:21
CentOS-8 - Base 0.0 B/s | 0 B 00:00
CentOS-8 - Extras 0.0 B/s | 0 B 00:00
Failed to synchronize cache for repo 'AppStream', ignoring this repo.
Failed to synchronize cache for repo 'BaseOS', ignoring this repo.
Failed to synchronize cache for repo 'extras', ignoring this repo.
Package wget-1.19.5-8.el8_1.1.x86_64 is already installed.
Dependencies resolved.
Nothing to do.
Complete!
原因是CentOS-Base.repo设置问题
解决方法，baseurl替换为阿里云镜像：
nano /etc/yum.repos.d/CentOS-Base.repo
# CentOS-Base.repo
#
# The mirror system uses the connecting IP address of the client and the
# update status of each mirror to pick mirrors that are updated to and
# geographically close to the client. You should use this for CentOS updates
# unless you are manually picking other mirrors.
#
# If the mirrorlist= does not work for you, as a fall back you can try the
# remarked out baseurl= line instead.
#
#
[BaseOS]
name=CentOS-$releasever - Base
baseurl=https://mirrors.aliyun.com/centos/$releasever/BaseOS/$basearch/os/
#baseurl=http://120.125.0.40/centos/$releasever/BaseOS/$basearch/os/
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=BaseOS&infra=$infra
enabled=1
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-centosofficial
[AppStream]
name=CentOS-$releasever - AppStream
baseurl=https://mirrors.aliyun.com/centos/$releasever/AppStream/$basearch/os/
#baseurl=http://120.125.0.40/centos/$releasever/AppStream/$basearch/os/
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=AppStream&infra=$infra
enabled=1
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-centosofficial
[PowerTools]
name=CentOS-$releasever - PowerTools
baseurl=https://mirrors.aliyun.com/centos/$releasever/PowerTools/$basearch/os/
#baseurl=http://120.125.0.40/centos/$releasever/PowerTools/$basearch/os/
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=PowerTools&infra=$infra
enabled=0
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-centosofficial
#additional packages that may be useful
[extras]
name=CentOS-$releasever - Extras
baseurl=https://mirrors.aliyun.com/centos/$releasever/extras/$basearch/os/
#baseurl=http://120.125.0.40/centos/$releasever/extras/$basearch/os/
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=extras
enabled=1
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-centosofficial
#additional packages that extend functionality of existing packages
[centosplus]
name=CentOS-$releasever - Plus
baseurl=https://mirrors.aliyun.com/centos/$releasever/centosplus/$basearch/os/
#baseurl=http://120.125.0.40/centos/$releasever/centosplus/$basearch/os/
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=centosplus
gpgcheck=1
enabled=0
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-centosofficial
随后：
dnf clean all # 清除所有的缓存文件
dnf makecache # 制作元数据缓存
