1、停掉mysql

1.1單實例停止方式

[root@qiuhom ~]# /etc/init.d/mysqld stop
Shutting down MySQL.                                       [  OK  ]

　　1.2多實例停止方式　

[root@qiuhom ~]# /data/3306/mysql stop
Stopping MySQL ... 　

當然停止mysqld的方式有很多比如也可以用kill -9 +mysqld的pid號,killall mysqld 或者pkill mysqld都可以將進程殺死，但是這種簡單粗暴的方式我們不推薦。

2、用mysqld_safe 啟動數據庫

2.1單實例啟動

[root@qiuhom ~]# mysqld_safe --skip-grant-tables --user=mysql &
[1] 1285
[root@qiuhom ~]# 181004 17:23:52 mysqld_safe Logging to ‘/application/mysql-5.5.32/data/qiuhom.err‘.
181004 17:23:52 mysqld_safe Starting mysqld daemon with databases from /application/mysql-5.5.32/data

[root@qiuhom ~]# mysql
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 1
Server version: 5.5.32-log Source distribution

Copyright (c) 2000, 2013, 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> 

提示：用mysqld_safe啟動數據庫一定要加--skip-grant-tables 忽略授權表的方式啟動，當然也要指定用戶。

通過以上mysqld_safe啟動後此時登錄數據庫就沒有密碼了 我可以mysql直接進入 也可以mysql -uroot -p 回車 密碼為空直接回車
也可以進入數據庫

2.2多實例啟動

[root@qiuhom ~]# mysqld_safe --defaults-file=/data/3306/my.cnf --skip-grant-tables &
[1] 798
[root@qiuhom ~]# 181003 10:16:53 mysqld_safe Logging to ‘/data/3306/mysql_lee3306.err‘.
181003 10:16:53 mysqld_safe Starting mysqld daemon with databases from /data/3306/data

[root@qiuhom ~]# mysql -S /data/3306/mysql.sock 
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 2
Server version: 5.5.32-log Source distribution

Copyright (c) 2000, 2013, 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> 

提示：多實例的啟動要指定啟動配置文件的位置，--defaults-file 就是用來指定啟動配置文件的位置。值得註意的是登錄多實例mysql 一定要指定mysql的sock文件

-S 來指定登錄mysql的sock文件位置

3、進入數據庫後，我們用update對mysql庫裏的user表進行修改

mysql> update mysql.user set password=password("admin123.com") where user=‘test‘ and host=‘localhost‘;
Query OK, 1 row affected (0.00 sec)
Rows matched: 1  Changed: 1  Warnings: 0

mysql> select user,host,password from mysql.user;
+------------+-----------+-------------------------------------------+
| user       | host      | password                                  |
+------------+-----------+-------------------------------------------+
| root       | localhost | *4ACFE3202A5FF5CF467898FC58AAB1D615029441 |
| root       | 127.0.0.1 |                                           |
| qiuhom     | %         | *4ACFE3202A5FF5CF467898FC58AAB1D615029441 |
| test       | localhost | *2D9AC2437F9E59A51BE8BA89A3D59E76F32F55E8 |
| test       | %         | *4ACFE3202A5FF5CF467898FC58AAB1D615029441 |
| qiuhom_db1 | localhost | *2D9AC2437F9E59A51BE8BA89A3D59E76F32F55E8 |
| qiuhom_db2 | localhost | *2D9AC2437F9E59A51BE8BA89A3D59E76F32F55E8 |
+------------+-----------+-------------------------------------------+
7 rows in set (0.00 sec)
mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)　

提示：設置的密碼我不能直接寫password=“xxx” ,一定要用password函數將自己設置的密碼加密，我們在數據庫裏看到的都是密文密碼。用update 修改表裏的內容

一定要註意 後面一定要條件，條件越多越精確。最後不要忘記刷新權限喲！！！

4、停止掉mysqld_safe啟動的數據庫，重新以正常的方式啟動數據庫

4.1停止mysqld_safe啟動的數據庫實例（單實例）

[root@qiuhom ~]# mysqladmin -utest -padmin123.com shutdown
181004 17:53:37 mysqld_safe mysqld from pid file /application/mysql-5.5.32/data/qiuhom.pid ended
[1]+  Done                    mysqld_safe --skip-grant-tables --user=mysql
[root@qiuhom ~]# ps -ef |grep mysql|grep -v grep 
[root@qiuhom ~]# 

　　4.2停止mysqld_safe啟動的數據庫實例（多實例）

[root@qiuhom ~]# mysqladmin -utest -padmin123.com -S /data/3306/mysql.sock shutdown
181003 10:46:59 mysqld_safe mysqld from pid file /data/3306/mysqld.pid ended
[1]+  Done                    mysqld_safe --defaults-file=/data/3306/my.cnf --skip-grant-tables
[root@qiuhom ~]# ps -ef |grep 3306|grep -v grep 
[root@qiuhom ~]# 

　　4.3正常啟動mysql(單實例)

[root@qiuhom ~]# /etc/init.d/mysqld start
Starting MySQL                                             [  OK  ]
[root@qiuhom ~]# mysql -utest -padmin123.com
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 3
Server version: 5.5.32-log Source distribution

Copyright (c) 2000, 2013, 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> 

　　4.4正常啟動mysql（多實例）

[root@qiuhom ~]# /data/3306/mysql start
Starting MySQL...
[root@qiuhom ~]# mysql -utest -padmin123.com -S /data/3306/mysql.sock 
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 1
Server version: 5.5.32-log Source distribution

Copyright (c) 2000, 2013, 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> 

提示：以上是忘記密碼，重新設置密碼的流程 不要和mysqladmin混淆，mysqladmin用於空密碼設置密碼或者知道密碼修改密碼。多實例的啟動一定要加--defaults-file來指定啟動配置文件，登錄多實例

一定要用-S（大寫）指定mysql的sock文件。。

mysql忘記密碼怎麽辦？？