root密码忘记，重置mysql的root密码：
一、修改mysql的配置文件my.cnf
1.在[mysqld]的段中加上一句：skip-grant-tables
[mysqld]
datadir=/var/lib/mysql
socket=/var/lib/mysql/mysql.sock
skip-name-resolve
skip-grant-tables
保存并且退出vi。
（或执行 mysqld_safe --skip-grant-tables &）
2.重新启动mysqld
# /etc/init.d/mysqld restart
Stopping MySQL: [ OK ]
Starting MySQL: [ OK ]
3.登录并修改MySQL的root密码
# /usr/bin/mysql
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 3 to server version: 3.23.56
Type 'help;' or '\h' for help. Type '\c' to clear the buffer.
mysql> use mysql ;
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> UPDATE user SET Password = password ( 'new-password' ) WHERE User = 'root' ;
Query OK, 0 rows affected (0.00 sec)
Rows matched: 2 Changed: 0 Warnings: 0
mysql> flush privileges ;
Query OK, 0 rows affected (0.01 sec)
mysql> quit
Bye
4.将MySQL的登录设置修改回来
# vi /etc/my.cnf
将刚才在[mysqld]的段中加上的skip-grant-tables删除
保存并且退出vi。
5．重新启动mysqld
# /etc/init.d/mysqld restart
Stopping MySQL: [ OK ]
Starting MySQL: [ OK ]
二、
停止mysql服务
/etc/init.d/mysqld stop
sudo mysqld_safe --skip-grant-table&
mysql
use mysql;
update user set password = password('yourpasswd') where user = 'root';
flush privileges;
重启下mysql服务即可重新用新密码登录
/etc/init.d/mysqld restart
允许远程连接mysql
通过navicat连接MySQL的时候发生的这个错误
ERROR 1130: Host ***.***.***.*** is not allowed to connect to this MySQL server
说明所连接的用户帐号没有远程连接的权限，只能在本机(localhost)登录。
需更改 MySQL 数据库里的 user表里的 host项
把localhost改称%
一、
登陆到MySQL ，首先 use MySQL；
按照别人提供的方式update的时候，出现错误。
MySQL> update user set host='%' where user = 'root';
ERROR 1062 (23000): Duplicate entry '%-root' for key 'PRIMARY'
然后查看了下数据库的host信息如下：
MySQL> select host from user where user = 'root';
+-----------------------+
| host |
+-----------------------+
| % |
| 127.0.0.1 |
| localhost.localdomain |
+-----------------------+
3 rows in set (0.00 sec)
host已经有了%这个值，所以直接运行命令：
MySQL>flush privileges;
二、
mysql> grant all privileges on *.* to 'root'@'%' with grant option;
Query OK, 0 rows affected (0.02 sec)
mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)
mysql> selectuser.host from user;
+-----------+--------------+
| user| host|
+-----------+--------------+
| root| %|
| root| 127.0.0.1|
| repl_user | 192.168.1.52 |
+-----------+--------------+
3 rows in set (0.00 sec)
允许指定IP访问mysql
mysql> grant all privileges on *.* to 'root'@***.***.***.**** identified by '123456';
QueryOK, 0 rows affected (0.00 sec)