开启MySQL远程访问权限 允许远程连接（阿里云服务器）、linux关闭防火墙

1.登陆mysql：mysql -u root -p

mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
+--------------------+
4 rows in set (0.01 sec)
 
mysql> use mysql;   # 切换到mysql数据库
  Reading table information for completion of table and column names
  You can turn off this feature to get a quicker startup with -A
 
  Database changed
mysql> select host,user from user;  # 查询user表
  +-----------+---------------+
  | host      | user          |
  +-----------+---------------+
  | %         | root          |
  | localhost | mysql.session |
  | localhost | mysql.sys     |
  +-----------+---------------+
  5 rows in set (0.00 sec)

如果上述查询结果，root用户对应的host不为%，则修改用户权限

mysql> GRANT ALL PRIVILEGES ON *.* TO 'root'@'%' IDENTIFIED BY 'root密码' WITH GRANT OPTION;   # 修改权限
  Query OK, 0 rows affected, 1 warning (0.00 sec)
 
mysql> FLUSH PRIVILEGES;
  Query OK, 0 rows affected (0.00 sec)

或创建用户

mysql>insert into user (host,user,password) values('122.114.155.163','admin',password('ygpassword'));
 
mysql>FLUSH PRIVILEGES;
 
mysql>GRANT ALL PRIVILEGES ON *.* TO 'admin'@'122.114.155.163'IDENTIFIED BY 'ygpassword' WITH GRANT OPTION;

mysql>FLUSH PRIVILEGES;

完成。（如果连接不成功，继续执行下面操作）

2.阿里云的ECS需要手动添加安全组规则

3.关闭防火墙（关闭防火墙，就可以外部访问了。不受端口限制。生产环境，最好开启防火墙，开启部分端口。）

1.永久有效

 开启： chkconfig iptables on
 关闭： chkconfig iptables off

2.即刻生效

 开启： service iptables start
 关闭： service iptables stop 

3.开启部分端口

 vim /etc/sysconfig/iptables

添加想要开启的相关端口

 -A INPUT -m state --state NEW -m tcp -p tcp --dport  -j ACCEPT
 -A INPUT -m state --state NEW -m tcp -p tcp --dport  -j ACCEPT
 -A INPUT -m state --state NEW -m tcp -p tcp --dport  -j ACCEPT
 -A INPUT -m state --state NEW -m tcp -p tcp --dport  -j ACCEPT
 -A INPUT -m state --state NEW -m tcp -p tcp --dport  -j ACCEPT

4.重启防火墙服务

 service iptables restart 

方法4：（腾讯云）
配置腾讯云服务器的安全组开放3306端口