1.Centos切换镜像源

1.打开配置yum所在文件，CentOS-Base.repo

vi /etc/yum.repos.d/CentOS-Base.repo

2.将CentOS-Base.repo里的内容全部替换为以下内容

# CentOS-Base.repo   
[base]  
name=CentOS-$releasever - Base  
baseurl=http://mirrors.aliyun.com/centos/$releasever/os/$basearch/  
        http://mirrors.tuna.tsinghua.edu.cn/centos/$releasever/os/$basearch/  
gpgcheck=1  
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7  
  
#released updates   
[updates]  
name=CentOS-$releasever - Updates  
baseurl=http://mirrors.aliyun.com/centos/$releasever/updates/$basearch/  
        http://mirrors.tuna.tsinghua.edu.cn/centos/$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-$releasever - Extras  
baseurl=http://mirrors.aliyun.com/centos/$releasever/extras/$basearch/  
        http://mirrors.tuna.tsinghua.edu.cn/centos/$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-$releasever - Plus  
baseurl=http://mirrors.aliyun.com/centos/$releasever/centosplus/$basearch/  
        http://mirrors.tuna.tsinghua.edu.cn/centos/$releasever/centosplus/$basearch/  
gpgcheck=1  
enabled=0  
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7  
  
#contrib - packages by Centos Users  
[contrib]  
name=CentOS-$releasever - Contrib  
baseurl=http://mirrors.aliyun.com/centos/$releasever/contrib/$basearch/  
        http://mirrors.tuna.tsinghua.edu.cn/centos/$releasever/contrib/$basearch/  
gpgcheck=1  
enabled=0  
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7  
  
# 使用failovermethod指定优先级，这里设置为随机（roundrobin），也可以改为priority并指定每个URL的优先级  
failovermethod=roundrobin

3.清理YUM缓存并更新

yum clean all

yum makecache

yum update