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报错信息如下：

The GPG keys listed for the "MySQL 5.7 Community Server" repository are already installed but they are not correct for this package.
Check that the correct key URLs are configured for this repository.


 Failing package is: mysql-community-server-5.7.37-1.el7.x86_64
 GPG Keys are configured as: file:///etc/pki/rpm-gpg/RPM-GPG-KEY-mysql
PS：Mysql 升级 GPG 导致密钥配置失败

出现上述提示原因是 Mysql 的 GPG 升级了，需要重新获取

解决办法，更新证书

rpm --import https://repo.mysql.com/RPM-GPG-KEY-mysql-2022

重新安装 Mysql 正常

1. Add the Mono repository to your system
   The package repository hosts the packages you need, add it with the following commands in a root shell.
   Note:the packages should work on newer CentOS/RHEL versions too but we only test the ones listed below.
   CentOS/RHEL 8(x86_64)

rpm --import "https://keyserver.ubuntu.com/pks/lookup?op=get&search=0x3FA7E0328081BFF6A14DA29AA6A19B38D3D831EF" 
su -c 'curl https://download.mono-project.com/repo/centos8-stable.repo | tee /etc/yum.repos.d/mono-centos8-stable.repo' 

CentOS/RHEL 7(x86_64)

rpm --import "https://keyserver.ubuntu.com/pks/lookup?op=get&search=0x3FA7E0328081BFF6A14DA29AA6A19B38D3D831EF" 
su -c 'curl https://download.mono-project.com/repo/centos7-stable.repo | tee /etc/yum.repos.d/mono-centos7-stable.repo' 

CentOS/RHEL 6(x86_64, i686)

rpm --import "https://keyserver.ubuntu.com/pks/lookup?op=get&search=0x3FA7E0328081BFF6A14DA29AA6A19B38D3D831EF" 
su -c 'curl https://download.mono-project.com/repo/centos6-stable.repo | tee /etc/yum.repos.d/mono-centos6-stable.repo' 

2. Install Mono

yum install mono-devel

（The package mono-devel should be installed to compile code. ） 阅读全文

在虚拟机上安装了 centOs7 最小化方式安装后，登陆系统发现没有pip，现在给出简单方法安装如下：

yum -y install epel-release
yum install python-pip