使用字符串替换

我这里的操作参考了https://baijiahao.baidu.com/s?id=1708418392526536542&wfr=spider&for=pc这篇文章，https://mirrors.tuna.tsinghua.edu.cn/help/centos/是清华大学官网教程。
/etc/yum.repos.d/CentOS-Base.repo文件如下：

# 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.
#
#

[base]
name=CentOS-$releasever - Base
mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=os&infra=$infra
#baseurl=http://mirror.centos.org/centos/$releasever/os/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7

#released updates
[updates]
name=CentOS-$releasever - Updates
mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=updates&infra=$infra
#baseurl=http://mirror.centos.org/centos/$releasever/updates/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7

#additional packages that may be useful
[extras]
name=CentOS-$releasever - Extras
mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=extras&infra=$infra
#baseurl=http://mirror.centos.org/centos/$releasever/extras/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7

#additional packages that extend functionality of existing packages
[centosplus]
name=CentOS-$releasever - Plus
mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=centosplus&infra=$infra
#baseurl=http://mirror.centos.org/centos/$releasever/centosplus/$basearch/
gpgcheck=1
enabled=0
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7

这样的话需要使用

sudo sed -e 's|^mirrorlist=|#mirrorlist=|g' 
 -e 's|^#baseurl=http://mirror.centos.org|baseurl=http://mirrors.aliyun.com|g' 
 -i.bak 
 /etc/yum.repos.d/CentOS-Base.repo

先进行备份，然后再替换字符串。

现在是备份好了，字符串也替换好了。
yum clean all清除缓存。

yum makecache更新缓存。

yum repolist查看一下yum源是否配置成功。若是能够出现多条记录就是配置成功了，其实这些是配置源里的包，一般都有上万个包。

通过网上下载CentOS-Base.repo

若是不想像上边进行配置的话，使用cp /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.bak将CentOS-Base.repo复制为CentOS-Base.repo.bak。
然后使用下边三个wget命令中一个就可以获取.repo文件，只需要执行一次。
wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo可以获取阿里云yum源配置文件到/etc/yum.repos.d/目录下并更名为CentOS-Base.repo。
wget -O /etc/yum.repos.d/CentOS-Base.repo https://repo.huaweicloud.com/repository/conf/CentOS-7-reg.repo可以获取华为云yum源配置文件到/etc/yum.repos.d/目录下并更名为CentOS-Base.repo。
wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.163.com/.help/CentOS6-Base-163.repo获取网易yum源配置文件到/etc/yum.repos.d/目录下并更名为CentOS-Base.repo。
然后再依次执行下边的命令：
yum clean all清除缓存。
yum makecache更新缓存。
yum repolist查看一下yum源是否配置成功。