#启动
]# systemctl start mysqld
Job for mysqld.service failed because the control process exited with error code. See "systemctl status mysqld.service" and "journalctl -xe" for details.

#查看日志，ibdata1没有写权限
vim /var/log/mysqld.log 
2018-12-26T02:51:14.894580Z 1 [ERROR] [MY-012271] [InnoDB] The innodb_system data file 'ibdata1' must be writable
2018-12-26T02:51:14.894641Z 1 [ERROR] [MY-012278] [InnoDB] The innodb_system data file 'ibdata1' must be writable
#修改所有mysql目录及文件属主为mysql
chown -R mysql. /var/lib/   mysql*
#再次启动，成功
systemctl start mysqld 
#查看状态
]# systemctl status mysqld
?.mysqld.service - MySQL Server
   Loaded: loaded (/usr/lib/systemd/system/mysqld.service; enabled; vendor preset: disabled)
   Active: active (running) since Wed 2018-12-26 10:57:21 CST; 4min 11s ago

• 5.数据库管理

-- 创建账号、分配权限
CREATE USER 'user'@'localhost' IDENTIFIED BY 'password';
GRANT ALL PRIVILEGES ON *.* TO 'user'@'localhost' WITH GRANT OPTION
-- 修改密码，使数据库可以连接Navicat
ALTER USER 'user'@'%' IDENTIFIED WITH mysql_native_password BY 'password';
-- 刷新权限
FLUSH PRIVILEGES;
-- 显示账号及权限相关信息
SHOW GRANTS FOR 'user'@'localhost'; 

• 6. redis安装
     • https://redis.io/download