91.mysql的安装

安装MySQL：

1. 清除掉所有跟mariadb相关的东西
   yum list installed | grep mariadb | awk '{print $1}' | xargs yum erase -y
2. 清理之前的数据和日志文件（如果存在）
   rm -rf /var/lib/mysql
   rm -f /var/log/mysqld.log
3. 下载MySQL官方提供的RPM包并解归档
   wget https://dev.mysql.com/get/Downloads/MySQL-5.7/mysql-5.7.28-1.el7.x86_64.rpm-bundle.tar
   tar -xf mysql-5.7.28-1.el7.x86_64.rpm-bundle.tar
4. 使用rpm包管理工具安装MySQL
   rpm -ivh mysql-community-common-...rpm
   rpm -ivh mysql-community-libs-...rpm
   rpm -ivh mysql-community-client-...rpm
   rpm -ivh mysql-community-server-...rpm
5. 启动服务查看随机密码
   systemctl start mysqld
   cat /var/log/mysqld.log | grep password
6. 用客户端工具连接MySQL
   mysql -u root -p
7. 修改root用户口令
   set global validate_password_policy=0;
   set global validate_password_length=6;
   alter user 'root'@'localhost' identified by '123456';
   安装Python3
8. 安装依赖项
   yum install -y zlib-devel bzip2-devel openssl-devel ncurses-devel sqlite-devel readline-devel tk-devel gdbm-devel db4-devel libpcap-devel xz-devel libffi-devel
9. 下载Python3源代码
   wget https://www.python.org/ftp/python/3.7.6/Python-3.7.6.tar.xz
10. 解压缩和解归档
    xz -d Python-3.7.6.tar.xz
    tar -xvf Python-3.7.6.tar
11. 执行安装前的配置
    cd Python-3.7.6
    ./configure --prefix=/usr/local/python37 --enable-optimizations
12. 构建和安装
    make && make install
13. 注册环境变量
    vim ~/.bash_profile

PATH=$PATH:/usr/local/python37/bin
export PATH