前言：epel源为“红帽系”的操作系统提供的额外的软件包，适用于RHEL，CentOS，

在安装ansible和其他软件时。会使用到epel源。

在安装epel源之前，首先安装一个叫：epel-release的软件包，这个软件包会自动配置yum仓库。

好，废话不多说，下面开始配置epel源

1.移除系统自带的yum仓库

[root@www82 ~]# cd /etc/yum.repos.d/   ###进入到yum仓库的目录

[root@www82 yum.repos.d]# ls        #####发现系统自带的yum仓库，创建个bak目录，把系统自带地yum 
                                                       仓库，全部移地bak目录中
bak               CentOS-CR.repo         CentOS-fasttrack.repo  CentOS-Sources.repo  rhe17.repo
CentOS-Base.repo  CentOS-Debuginfo.repo  CentOS-Media.repo      CentOS-Vault.repo

[root@www82 yum.repos.d]# mv C* bak/    ######把系统自带地yum仓库，全部移地bak目录中

[root@www82 yum.repos.d]# ls   ######在查看，只保留一个自己配的yum源，
bak  rhe17.repo

2.到阿里开源镜像中下载相应的repo文件，注意：此操作需要联网，需要把网卡的网关和DNS设置好，此操作需要用到wget软件包，没有的直接：yum  -y  install  wget去安装

[root@www82 yum.repos.d]# wget http://mirrors.aliyun.com/repo/Centos-7.repo
           #####下载repo文件，下面的是下载过程
--2021-08-10 06:20:48--  http://mirrors.aliyun.com/repo/Centos-7.repo
Resolving mirrors.aliyun.com (mirrors.aliyun.com)... 111.6.227.173, 111.6.234.239, 111.6.227.174, ...
Connecting to mirrors.aliyun.com (mirrors.aliyun.com)|111.6.227.173|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 2523 (2.5K) [application/octet-stream]
Saving to: ‘Centos-7.repo’

100%[============================================================================================================>] 2,523       --.-K/s   in 0s      
2021-08-10 06:20:48 (359 MB/s) - ‘Centos-7.repo’ saved [2523/2523]   


[root@www82 yum.repos.d]# ls   ###再次查看，发现已经下载Centos-7.repo文件，
bak  Centos-7.repo  rhe17.repo

[root@www82 yum.repos.d]# mv rhe17.repo bak/    ###把自己配的本地yum源，也移动到bak目录中，
[root@www82 yum.repos.d]# ls    ######只保留刚才下载的repo文件
bak  Centos-7.repo

3.清楚缓存，重新生成缓存

[root@www82 yum.repos.d]# yum clean all    ###清楚缓存


[root@www82 yum.repos.d]# yum makecache   ###生成缓存

4.安装epel源

[root@www82 yum.repos.d]#  yum install -y epel-release   ###下载epel源
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
 * base: mirrors.aliyun.com
 * extras: mirrors.aliyun.com
 * updates: mirrors.aliyun.com
Resolving Dependencies
--> Running transaction check
---> Package epel-release.noarch 0:7-11 will be installed
--> Finished Dependency Resolution

Dependencies Resolved

======================================================================================================================================================
......   ###此处省略                                            

Installed:
  epel-release.noarch 0:7-11                                                                                                                          

Complete!  ###下载完成

[root@www82 yum.repos.d]# ls   ###在此查看又多出来两个repo文件
bak  Centos-7.repo  epel.repo  epel-testing.repo

5.使用阿里开源镜像提供的epel源

[root@www82 yum.repos.d]# wget -O /etc/yum.repos.d/epel-7.repo http://mirrors.aliyun.com/repo/epel-7.repo    ###下载epelyum源
--2021-08-10 06:34:45--  http://mirrors.aliyun.com/repo/epel-7.repo
Resolving mirrors.aliyun.com (mirrors.aliyun.com)... 111.6.234.240, 111.6.252.118, 111.6.252.115, ...
Connecting to mirrors.aliyun.com (mirrors.aliyun.com)|111.6.234.240|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 664 [application/octet-stream]
Saving to: ‘/etc/yum.repos.d/epel-7.repo’

100%[============================================================================================================>] 664         --.-K/s   in 0s      

2021-08-10 06:34:45 (92.1 MB/s) - ‘/etc/yum.repos.d/epel-7.repo’ saved [664/664]

[root@www82 yum.repos.d]# ls     ###在查看又多一个repo文件
bak  Centos-7.repo  epel-7.repo  epel.repo  epel-testing.repo

6.清除缓存，重新生成缓存

[root@www82 yum.repos.d]# yum clean all    ###清除缓存
Loaded plugins: fastestmirror
Repository epel is listed more than once in the configuration
Repository epel-debuginfo is listed more than once in the configuration
Repository epel-source is listed more than once in the configuration
Cleaning repos: base epel extras updates
Cleaning up everything
Maybe you want: rm -rf /var/cache/yum, to also free up space taken by orphaned data from disabled or removed repos
Cleaning up list of fastest mirrors

[root@www82 yum.repos.d]# yum makecache    ###生成缓存
Loaded plugins: fastestmirror
Repository epel is listed more than once in the configuration
Repository epel-debuginfo is listed more than once in the configuration
Repository epel-source is listed more than once in the configuration
Determining fastest mirrors
 * base: mirrors.aliyun.com
 * extras: mirrors.aliyun.com
 * updates: mirrors.aliyun.com
base                                                                                                                           | 3.6 kB  00:00:00     
epel                                                                                                                           | 4.7 kB  00:00:00     
extras                                                                                                                         | 2.9 kB  00:00:00     
updates                                                                                                                        | 2.9 kB  00:00:00     
(1/16): base/7/x86_64/group_gz                                                                                                 | 153 kB  00:00:00     
(2/16): base/7/x86_64/filelists_db                                                                                             | 7.2 MB  00:00:03     
(3/16): base/7/x86_64/primary_db                                                                                               | 6.1 MB  00:00:02     
(4/16): epel/x86_64/group_gz                                                                                                   |  96 kB  00:00:00     
(5/16): epel/x86_64/updateinfo                                                                                                 | 1.0 MB  00:00:00     
(6/16): epel/x86_64/prestodelta                                                                                                | 2.8 kB  00:00:00     
(7/16): base/7/x86_64/other_db                                                                                                 | 2.6 MB  00:00:01     
(8/16): epel/x86_64/primary_db                                                                                                 | 6.9 MB  00:00:03     
(9/16): extras/7/x86_64/primary_db                                                                                             | 242 kB  00:00:00     
(10/16): extras/7/x86_64/filelists_db                                                                                          | 235 kB  00:00:00     
(11/16): extras/7/x86_64/other_db                                                                                              | 143 kB  00:00:00     
(12/16): epel/x86_64/other_db                                                                                                  | 3.4 MB  00:00:02     
(13/16): updates/7/x86_64/filelists_db                                                                                         | 5.5 MB  00:00:03     
(14/16): updates/7/x86_64/other_db                                                                                             | 688 kB  00:00:00     
(15/16): updates/7/x86_64/primary_db                                                                                           | 9.6 MB  00:00:05     
(16/16): epel/x86_64/filelists_db                                                                                              |  12 MB  00:00:09     
Metadata Cache Created

7.测试epel源------>安装ansible，nginx

[root@www82 yum.repos.d]# yum install -y ansible    ###安装ansible
Loaded plugins: fastestmirror
Repository epel is listed more than once in the configuration
Repository epel-debuginfo is listed more than once in the configuration
Repository epel-source is listed more than once in the configuration
Loading mirror speeds from cached hostfile
 * base: mirrors.aliyun.com
 * extras: mirrors.aliyun.com
 * updates: mirrors.aliyun.com
Resolving Dependencies
--> Running transaction check
---> Package ansible.noarch 0:2.9.23-1.el7 will be installed
       
            ...... 此处省略
Installed:
  ansible.noarch 0:2.9.23-1.el7                                                                                                                     

Dependency Installed:
  PyYAML.x86_64 0:3.10-11.el7               libyaml.x86_64 0:0.1.4-11.el7_0                                python-babel.noarch 0:0.9.6-8.el7        
  python-backports.x86_64 0:1.0-8.el7       python-backports-ssl_match_hostname.noarch 0:3.5.0.1-1.el7     python-cffi.x86_64 0:1.6.0-5.el7         
  python-enum34.noarch 0:1.0.4-1.el7        python-idna.noarch 0:2.4-1.el7                                 python-ipaddress.noarch 0:1.0.16-2.el7   
  python-jinja2.noarch 0:2.7.2-4.el7        python-markupsafe.x86_64 0:0.11-10.el7                         python-paramiko.noarch 0:2.1.1-9.el7     
  python-ply.noarch 0:3.4-11.el7            python-pycparser.noarch 0:2.14-1.el7                           python-setuptools.noarch 0:0.9.8-7.el7   
  python-six.noarch 0:1.9.0-2.el7           python2-cryptography.x86_64 0:1.7.2-2.el7                      python2-httplib2.noarch 0:0.18.1-3.el7   
  python2-jmespath.noarch 0:0.9.4-2.el7     python2-pyasn1.noarch 0:0.1.9-7.el7                            sshpass.x86_64 0:1.06-2.el7              

Complete!   ######完成安装，说明epel源可用