2020-12-10 晚上，为了实现从php7.1 平滑升级到php7.3，根据 https://blog.csdn.net/baidu_35297131/article/details/89960654 这篇文章修改了yum相关配置文件，结果php升级没成功，yum也无法使用，只能卸载重装
卸载：
# rpm -qa|grep yum|xargs rpm -ev --allmatches --nodeps
# whereis yum |xargs rm -frv重装：
在重装时由于依赖问题一直报错：
error: Failed dependencies:
/usr/bin/python is needed by yum-3.4.3-163.el7.centos.noarch
python >= 2.4 is needed by yum-3.4.3-163.el7.centos.noarch
python(abi) = 2.7 is needed by yum-3.4.3-163.el7.centos.noarch
python-iniparse is needed by yum-3.4.3-163.el7.centos.noarch
python-sqlite is needed by yum-3.4.3-163.el7.centos.noarch
python-urlgrabber >= 3.10-8 is needed by yum-3.4.3-163.el7.centos.noarch
rpm-python is needed by yum-3.4.3-163.el7.centos.noarch
libpython2.7.so.1.0()(64bit) is needed by yum-metadata-parser-1.1.4-10.el7.x86_64
python(abi) = 2.7 is needed by yum-metadata-parser-1.1.4-10.el7.x86_64
1、查看yum安装包
# rpm -qa | grep yum
yum-plugin-fastestmirror-1.1.31-52.el7.noarch
yum-metadata-parser-1.1.4-10.el7.x86_64
yum-utils-1.1.31-52.el7.noarch
2、将其全部卸载
#rpm -e yum-plugin-fastestmirror-1.1.31-52.el7.noarch --nodeps
#rpm -e yum-metadata-parser-1.1.4-10.el7.x86_64 --nodeps
#rpm -e yum-utils-1.1.31-52.el7.noarch --nodeps
3、在http://mirrors.163.com/centos/7/os/x86_64/Packages/下载如下20个包（下面这些资源可以到 “csdn-我的资源" 里下载）
libxml2-python-2.9.1-6.el7_2.3.x86_64.rpm
python-ipaddress-1.0.16-2.el7.noarch.rpm
lvm2-python-libs-2.02.185-2.el7.x86_64.rpm
python-kitchen-1.1.1-5.el7.noarch.rpm
yum-3.4.3-163.el7.centos.noarch.rpm
python-2.7.5-86.el7.x86_64.rpm
python-libs-2.7.5-86.el7.x86_64.rpm
yum-metadata-parser-1.1.4-10.el7.x86_64.rpm
python-backports-ssl_match_hostname-3.5.0.1-1.el7.noarch.rpm
python-pycurl-7.19.0-19.el7.x86_64.rpm
yum-plugin-aliases-1.1.31-52.el7.noarch.rpm
python-chardet-2.2.1-3.el7.noarch.rpm
python-setuptools-0.9.8-7.el7.noarch.rpm
yum-plugin-fastestmirror-1.1.31-52.el7.noarch.rpm
python-devel-2.7.5-86.el7.x86_64.rpm
python-urlgrabber-3.10-9.el7.noarch.rpm
yum-plugin-protectbase-1.1.31-52.el7.noarch.rpm
python-iniparse-0.4-9.el7.noarch.rpm
rpm-python-4.11.3-40.el7.x86_64.rpm
yum-utils-1.1.31-52.el7.noarch.rpm
4、下载完成后执行
#rpm -Uvh --replacepkgs lvm2-python-libs*.rpm --nodeps --force
#rpm -Uvh --replacepkgs libxml2-python*.rpm --nodeps --force
#rpm -Uvh --replacepkgs python*.rpm --nodeps --force
#rpm -Uvh --replacepkgs rpm-python*.rpm yum*.rpm --nodeps --force
5、成功安装
6、如果将python换成python3的话，运行yum会报错
[root@iz2ze3ogy01eqvjs99e8nez python]# yum
File "/usr/bin/yum", line 30
except KeyboardInterrupt, e:
^
SyntaxError: invalid syntax
修改 vi /etc/usr/yum 第一行为
#!/usr/bin/python2
设置yum镜像源
1、进入yum镜像源配置文件夹
[root@localhost /]# cd /etc/yum.repos.d/2、备份系统原来的镜像文件
[root@localhost yum.repos.d]# mv CentOs-Base.repo CentOs-Base.repo.bak3、下载镜像源
163 yum镜像源：http://mirrors.163.com/.help/CentOS7-Base-163.repo
阿里云yum镜像源：http://mirrors.aliyun.com/repo/Centos-7.repo
[root@localhost yum.repos.d]# wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo或者
[root@localhost yum.repos.d]# wget http://mirrors.aliyun.com/repo/Centos-7.repo
[root@localhost yum.repos.d]# mv Centos-7.repo CentOs-Base.repo #重命名镜像文件4、清除缓存
[root@localhost yum.repos.d]# yum clean all5、生成缓存
[root@localhost yum.repos.d]# yum makecache6、升级更新
[root@localhost yum.repos.d]# yum -y update #升级所有包同时也升级软件和系统内核或
[root@localhost yum.repos.d]# yum -y upgrade #只升级所有包，不升级软件和系统内核