1、yum clean all 后导致yum报错 
一开始因为yum找不到包,所以打算更新一下yum仓库,结果遇到坑的博客直接yum不能使用了  使用yum update报错  
[root@iZbp17aznee2whyk4k44vjZ ~]# yum update httpd
base                                                                                                                                                                                                                        | 3.6 kB  00:00:00     
extras                                                                                                                                                                                                                      | 2.9 kB  00:00:00     
updates                                                                                                                                                                                                                     | 2.9 kB  00:00:00     
No packages marked for update
  
感觉是yum的仓库给清理里没有包了  
[root@iZbp17aznee2whyk4k44vjZ ~]# yum update httpd-tools
Resolving Dependencies
--> Running transaction check
---> Package httpd-tools.x86_64 0:2.4.6-90.el7.centos will be updated
--> Processing Dependency: httpd-tools = 2.4.6-90.el7.centos for package: httpd-2.4.6-90.el7.centos.x86_64
---> Package httpd-tools.x86_64 0:2.4.6-97.el7.centos.5 will be an update
--> Finished Dependency Resolution
Error: Package: httpd-2.4.6-90.el7.centos.x86_64 (@base)
           Requires: httpd-tools = 2.4.6-90.el7.centos
           Removing: httpd-tools-2.4.6-90.el7.centos.x86_64 (@base)
               httpd-tools = 2.4.6-90.el7.centos
           Updated By: httpd-tools-2.4.6-97.el7.centos.5.x86_64 (updates)
               httpd-tools = 2.4.6-97.el7.centos.5
           Available: httpd-tools-2.4.6-95.el7.centos.x86_64 (base)
               httpd-tools = 2.4.6-95.el7.centos
           Available: httpd-tools-2.4.6-97.el7.centos.x86_64 (updates)
               httpd-tools = 2.4.6-97.el7.centos
           Available: httpd-tools-2.4.6-97.el7.centos.1.x86_64 (updates)
               httpd-tools = 2.4.6-97.el7.centos.1
           Available: httpd-tools-2.4.6-97.el7.centos.2.x86_64 (updates)
               httpd-tools = 2.4.6-97.el7.centos.2
           Available: httpd-tools-2.4.6-97.el7.centos.4.x86_64 (updates)
               httpd-tools = 2.4.6-97.el7.centos.4
 You could try using --skip-broken to work around the problem
 You could try running: rpm -Va --nofiles --nodigest
  
看到上面最后一句报错让我尝试rpm-Va --nofiles --nodigest  
[root@iZbp17aznee2whyk4k44vjZ ~]
warning: /etc/yum/pluginconf.d/fastestmirror.conf saved as /etc/yum/pluginconf.d/fastestmirror.conf.rpmsave
warning: /etc/yum.conf saved as /etc/yum.conf.rpmsave
[root@iZbp17aznee2whyk4k44vjZ ~]
  
结果返回为空,我的yum依赖都没了     后来到网站上找了几个下载依赖的地址都下载报错     
Connecting to centos.ustc.edu.cn (centos.ustc.edu.cn)|202.141.160.110|:80... connected.
HTTP request sent, awaiting response... 404 Not Found
2022-10-19 10:13:06 ERROR 404: Not Found.
  
后来我直接访问这个地址直接是404  其实直接到官网下载就可以了  这时候你yum makecache肯定是-bash: /usr/bin/yum: No such file or directory  因为你这时候yum依赖  依旧还是没下载下来   
2、最终解决方案 
到官网下载对应依赖     你也可以直接  
[root@iZbp17aznee2whyk4k44vjZ ~]
[root@iZbp17aznee2whyk4k44vjZ ~]
[root@iZbp17aznee2whyk4k44vjZ ~]
  
   
然后你在安装一下  
rpm -ivh yum-*
  
   然后看安装结果     成功  yum一下看工具都回来了     如果你的yum源还是有问题建议你还是更新一下  
3、更新yum源 
切换到yum文件夹  
cd /etc/yum.repos.d
  
将原来的yum源给备份  
mv /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.backup
  
指定路径下载  
wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo
  
清除缓存  
yum clean all
  
生成缓存  
yum makecache
  
实际测试,可以用了     
总结 
yum工具没了重新安装yum  对应的三个工具  yum-metadata-parser-1.1.4-10.el7.x86_64.rpm  yum-plugin-fastestmirror-1.1.31-54.el7_8.noarch.rpm  yum-3.4.3-168.el7.centos.noarch.rpm 
                
                
                
        
        
    
  
 
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