Linux安装MySQL后无法通过IP地址访问处理方法

本文主要总结Linux安装Mysql后，其他主机访问不了MySQL数据库的原因和解决方法

环境说明：

MySQL 5.7.30
CentOS Linux release 7.6.1810 (Core)

创建完Mysql数据库后可以查看mysql 日志获取root 用户登录密码

[root@localhost mysql-5.7.30]# cat /var/log/mysqld.log

使用获取到的密码就可以登录数据库了，登录后显示mysql> 表示成功

[root@localhost etc]# mysql -u root -p
Enter password: 
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 2
Server version: 5.7.30

Copyright (c) 2000, 2020, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> 
mysql>

登录后root用户不能直接使用，会提示需要先重置密码，重置密码的时候可能会出现not stifsy current plicy错误。默认情况下密码长度是8位，如果希望密码简单好记，需要修改规则

mysql> set password for root@localhost=password("root");
ERROR 1819 (HY000): Your password does not satisfy the current policy requirements
mysql> 
mysql> set global validate_password_length=4;
Query OK, 0 rows affected (0.00 sec)

mysql> set global validate_password_policy=0;
Query OK, 0 rows affected (0.00 sec)

mysql> set password for root@localhost=password("root");
Query OK, 0 rows affected, 1 warning (0.00 sec)


mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
+--------------------+
4 rows in set (0.00 sec)

mysql> use mysql;
Database changed
mysql>

此时如果使用Navicat链接Mysql数据库是链接不上的，

Mysql数据库系统中，每一用户都有自己的用户名和密码，同时还有自己的主机名称，root用户默认的主机名称是 localhost, 所以只能localhost方法，不能使用其他主机访问。如果此时需要设置root用户其他主机也可以访问，修改后使用flush privileges 刷新权限，这样不用重启。

mysql> grant all privileges on *.* to 'root'@'%' identified by 'root';
Query OK, 0 rows affected, 1 warning (0.00 sec)

mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)

mysql> 
mysql> select user ,host from user;
+---------------+-------------+
| user          | host        |
+---------------+-------------+
| root          | %           |
| mysql.session | localhost   |
| mysql.sys     | localhost   |
| root          | localhost   |
+---------------+-------------+
4 rows in set (0.00 sec)

mysql>

此时使用IP访问也可能不成功，部分人可能访问数据库成功，部分人可能访问数据库库失败。如果访问链接失败，再查看my.cnf或者my.ini的配置，查找bind-address参数。将其注释或者修改为0.0.0.0或者服务器的IP地址。如果没有可以手写此配置

[root@localhost ~]# cd /etc
[root@localhost etc]# 
[root@localhost etc]# ls
adjtime                  ethertypes          ld.so.cache               plymouth        
crypttab                 hostname            my.cnf                    resolv.conf     tuned
csh.cshrc                hosts               my.cnf.d                  rpc             udev

[mysqld]
#
# Remove leading # and set to the amount of RAM for the most important data
# cache in MySQL. Start at 70% of total RAM for dedicated server, else 10%.
# innodb_buffer_pool_size = 128M
#
datadir=/var/lib/mysql
socket=/var/lib/mysql/mysql.sock
bind-address=0.0.0.0

# Disabling symbolic-links is recommended to prevent assorted security risks
symbolic-links=0

log-error=/var/log/mysqld.log
pid-file=/var/run/mysqld/mysqld.pid

到此又会有部分人访问数据库成功，部分人访问数据库仍然失败，如果还是悲剧的这部分人，还需要查看防火墙设置，Linux系统中，防火墙iptables可能会阻止MySQL的外部访问。使用下面的命令查看


[root@localhost etc]# sudo iptables -L
Chain INPUT (policy ACCEPT)
target     prot opt source               destination         
ACCEPT     tcp  --  anywhere             anywhere             tcp dpt:cslistener
ACCEPT     all  --  anywhere             anywhere             ctstate RELATED,ESTABLISHED

......略

此时列表中如果没有mysql 信息，那么可以执行下面的命令允许外部访问Myslq, 其中dport 指定3306， 3306是MySQL的默认端口。执行后再使用sudo iptables -L查看会出现mysql访问信息。如下

[root@localhost etc]# sudo  iptables -I INPUT -p tcp --dport 3306 -j ACCEPT
[root@localhost etc]# 
[root@localhost etc]# sudo iptables -L
Chain INPUT (policy ACCEPT)
target     prot opt source               destination         
ACCEPT     tcp  --  anywhere             anywhere             tcp dpt:mysql
ACCEPT     tcp  --  anywhere             anywhere             tcp dpt:cslistener
ACCEPT     all  --  anywhere             anywhere             ctstate RELATED,ESTABLISHED

......略

最后重启MySQL后就可以访问MySQL数据库了