CentOS7 yum安装报错“Could not resolve host: mirrorlist.centos.org； Name or service not known“之解决办法（换源）_could not resolve host: mirrorlist.centos.org; nam

yum安装出现错误如下：

yum install -y wget && wget -O install.sh https://download.bt.cn/install/install_6.0.sh && sh install.sh 12f2c1d72

ImportError: /lib64/libcrypto.so.10: version `OPENSSL_1.0.2' not found (required by /www/server/panel/pyenv/lib/python3.7/lib-dynload/_ssl.cpython-37m-x86_64-linux-gnu.so)

Loaded plugins: fastestmirror, langpacks
Could not retrieve mirrorlist http://mirrorlist.centos.org/?release=7&arch=x86_64&repo=os error was
14: curl#6 - "Could not resolve host: mirrorlist.centos.org; Name or service not known"

 One of the configured repositories failed (Unknown)

Loaded plugins: fastestmirror, langpacks
Could not retrieve mirrorlist http://mirrorlist.centos.org/?release=7&arch=x86_64&repo=os error was
14: curl#6 - "Could not resolve host: mirrorlist.centos.org; Name or service not known"

 One of the configured repositories failed (Unknown),
 and yum doesn't have enough cached data to continue. At this point the only
 safe thing yum can do is fail. There are a few ways to work "fix" this:

     1. Contact the upstream for the repository and get them to fix the problem.

     2. Reconfigure the baseurl/etc. for the repository, to point to a working
        upstream. This is most often useful if you are using a newer
        distribution release than is supported by the repository (and the
        packages for the previous distribution release still work).

     3. Disable the repository, so yum won't use it by default. Yum will then
        just ignore the repository until you permanently enable it again or use
        --enablerepo for temporary usage:

            yum-config-manager --disable <repoid>

     4. Configure the failing repository to be skipped, if it is unavailable.
        Note that yum will try to contact the repo. when it runs most commands,
        so will have to try and fail each time (and thus. yum will be be much
        slower). If it is a very temporary problem though, this is often a nice
        compromise:

            yum-config-manager --save --setopt=<repoid>.skip_if_unavailable=true

Cannot find a valid baseurl for repo: base/7/x86_64

【解决办法】

看到报错日志中加粗的字体，命令行ping mirrorlist.centos.org 不通。试着ping www.baidu.com是正常的，说明DNS解析没问题。基本确认是yum源的问题。

CentOS7更换镜像源

1、先安装wget

yum install -y wget

2、打开阿里镜像http://mirrors.aliyun.com/

点击，帮助，查看详情：

3、下载CentOS 7的对应的repo文件

wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo
#或者
curl -o /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo

4、更新镜像源

yum clean all

yum makecache

yum -y update

执行完上面三行命令就好了