1、停掉mysql
1.1单实例停止方式
[root@qiuhom ~]# /etc/init.d/mysqld stop Shutting down MySQL. [ OK ]
1.2多实例停止方式
[root@qiuhom ~]# /data/3306/mysql stop Stopping MySQL ...
当然停止mysqld的方式有很多比如也可以用kill -9 +mysqld的pid号,killall mysqld 或者pkill mysqld都可以将进程杀死，但是这种简单粗暴的方式我们不推荐。
2、用mysqld_safe 启动数据库
2.1单实例启动
[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启动数据库一定要加--skip-grant-tables 忽略授权表的方式启动，当然也要指定用户。
通过以上mysqld_safe启动后此时登录数据库就没有密码了 我可以mysql直接进入 也可以mysql -uroot -p 回车 密码为空直接回车也可以进入数据库
2.2多实例启动
[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：多实例的启动要指定启动配置文件的位置，--defaults-file 就是用来指定启动配置文件的位置。值得注意的是登录多实例mysql 一定要指定mysql的sock文件
-S 来指定登录mysql的sock文件位置
3、进入数据库后，我们用update对mysql库里的user表进行修改
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：设置的密码我不能直接写password=“xxx” ,一定要用password函数将自己设置的密码加密，我们在数据库里看到的都是密文密码。用update 修改表里的内容，一定要注意 后面一定要条件，条件越多越精确。最后不要忘记刷新权限哟！！！
4、停止掉mysqld_safe启动的数据库，重新以正常的方式启动数据库
4.1停止mysqld_safe启动的数据库实例（单实例）
[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启动的数据库实例（多实例）
[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正常启动mysql(单实例)
[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正常启动mysql（多实例）
[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：以上是忘记密码，重新设置密码的流程 不要和mysqladmin混淆，mysqladmin用于空密码设置密码或者知道密码修改密码。多实例的启动一定要加--defaults-file来指定启动配置文件，登录多实例一定要用-S（大写）指定mysql的sock文件。。