[root@hzswtb2-mpc ~]# mysql
ERROR 1045 (28000): Access denied for user ‘root‘@‘localhost‘ (using password: NO)

遇到：ERROR 1045 (28000): Access denied for user ‘root‘@‘localhost‘ (using password: NO)

网上找了很多的文章还是没有解决我的问题；

1.首先可以确认的是mysql 命令行 sql命令关键字是不区分大小写；在5.1.51版本；

2.先将正常启动的mysqld stop掉；

3.再以绕过root口令检查的方式 start mysqld；

以下是解决经过：

1.先将正常启动的mysqld stop掉

[root@hzswtb2-mpc ~]# service mysqld stop
Stopping mysqld:                                           [  OK  ]

2.用绕过root口令检查的方式 启动 mysql 服务器，并且让其在后头运行；

[root@hzswtb2-mpc ~]# mysqld_safe --user=mysql --skip-grant-tables --skip-networking &
[1] 25513
[root@hzswtb2-mpc ~]# 141215 15:00:16 mysqld_safe Logging to ‘/var/log/mysqld.log‘.
141215 15:00:16 mysqld_safe Starting mysqld daemon with databases from /var/lib/mysql

3. mysql回车，进入mysql shell，按照前人留下的方法， update user表中的 root 用户的密码，结果发现 0 rows affected，再select 细看是 user 表是空的；

[root@hzswtb2-mpc ~]# mysql
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 1
Server version: 5.1.51 Source distribution

mysql> UPDATE user SET PASSWORD=PASSWORD(‘123456‘) where USER=‘root‘;       
Query OK, 0 rows affected (0.00 sec)
Rows matched: 0  Changed: 0  Warnings: 0

mysql>  use mysql
Database changed
mysql> show tables;
+---------------------------+
| Tables_in_mysql           |
+---------------------------+
| columns_priv              |
| db                        |
| event                     |
| func                      |
| general_log               |
| help_category             |
| help_keyword              |
| help_relation             |
| help_topic                |
| host                      |
| ndb_binlog_index          |
| plugin                    |
| proc                      |
| procs_priv                |
| servers                   |
| slow_log                  |
| tables_priv               |
| time_zone                 |
| time_zone_leap_second     |
| time_zone_name            |
| time_zone_transition      |
| time_zone_transition_type |
| user                      |
+---------------------------+
23 rows in set (0.00 sec)

mysql> select * from user;
Empty set (0.00 sec)

4.在user表 insert 一个名称为root的用户； 

mysql> insert into user(Host,User,Password,Select_priv,Insert_priv) VALUES(‘localhost‘,‘root‘,PASSWORD(‘pass3‘),‘Y‘,‘Y‘);
Query OK, 1 row affected, 3 warnings (0.00 sec)

5.#看到有个root用户了；

mysql> select * from user                
    -> ;
+-----------+------+-------------------------------------------+-------------+-------------+-------------+-------------+-------------+-----------+-------------+---------------+--------------+-----------+------------+-----------------+------------+------------+--------------+------------+-----------------------+------------------+--------------+-----------------+------------------+------------------+----------------+---------------------+--------------------+------------------+------------+--------------+----------+------------+-------------+--------------+---------------+-------------+-----------------+----------------------+
| Host      | User | Password                                  | Select_priv | Insert_priv | Update_priv | Delete_priv | Create_priv | Drop_priv | Reload_priv | Shutdown_priv | Process_priv | File_priv | Grant_priv | References_priv | Index_priv | Alter_priv | Show_db_priv | Super_priv | Create_tmp_table_priv | Lock_tables_priv | Execute_priv | Repl_slave_priv | Repl_client_priv | Create_view_priv | Show_view_priv | Create_routine_priv | Alter_routine_priv | Create_user_priv | Event_priv | Trigger_priv | ssl_type | ssl_cipher | x509_issuer | x509_subject | max_questions | max_updates | max_connections | max_user_connections |
+-----------+------+-------------------------------------------+-------------+-------------+-------------+-------------+-------------+-----------+-------------+---------------+--------------+-----------+------------+-----------------+------------+------------+--------------+------------+-----------------------+------------------+--------------+-----------------+------------------+------------------+----------------+---------------------+--------------------+------------------+------------+--------------+----------+------------+-------------+--------------+---------------+-------------+-----------------+----------------------+
| localhost | root | *35B5E90BC4F5AE5D02ED515DF6B61141F24EDA02 | Y           | Y           | N           | N           | N           | N         | N           | N             | N            | N         | N          | N               | N          | N          | N            | N          | N                     | N                | N            | N               | N                | N                | N              | N                   | N                  | N                | N          | N            |          |            |             |              |             0 |           0 |               0 |                    0 |
+-----------+------+-------------------------------------------+-------------+-------------+-------------+-------------+-------------+-----------+-------------+---------------+--------------+-----------+------------+-----------------+------------+------------+--------------+------------+-----------------------+------------------+--------------+-----------------+------------------+------------------+----------------+---------------------+--------------------+------------------+------------+--------------+----------+------------+-------------+--------------+---------------+-------------+-----------------+----------------------+
1 row in set (0.00 sec)

6 再更新 root 用户的密码，也能返回成功了；

mysql> UPDATE user SET Password = PASSWORD(‘newpass‘) WHERE user = ‘root‘;
Query OK, 1 row affected (0.00 sec)
Rows matched: 1  Changed: 1  Warnings: 0

mysql> FLUSH PRIVILEGES;
Query OK, 0 rows affected (0.00 sec)

mysql> exit

7.stop 刚才的 mysql服务，以正常方式重新启动mysql 服务器，mysql -u root -p  密码是newpass

[root@hzswtb2-mpc ~]# service mysqld stop
141215 16:12:24 mysqld_safe mysqld from pid file /var/run/mysqld/mysqld.pid ended
Stopping mysqld:                                           [  OK  ]
[1]+  Done                    mysqld_safe --user=mysql --skip-grant-tables --skip-networking
[root@hzswtb2-mpc ~]# service mysqld start
Starting mysqld:                                           [  OK  ]
[root@hzswtb2-mpc ~]#
[root@hzswtb2-mpc ~]# mysql
ERROR 1045 (28000): Access denied for user ‘root‘@‘localhost‘ (using password: NO)
[root@hzswtb2-mpc ~]# mysql -u root -p
Enter password:
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 4
Server version: 5.1.51 Source distribution

Copyright (c) 2000, 2010, Oracle and/or its affiliates. All rights reserved.
This software comes with ABSOLUTELY NO WARRANTY. This is free software,
and you are welcome to modify and redistribute it under the GPL v2 license

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

mysql>

mysql 安装完成后登陆不了mysql的 shell 即mysql>遇到：ERROR 1045 (28000): Access denied for user 'root'@'localhost‘