MySQL修改密码
===

## mysqld_safe不存在修改密码

1. 停止 MySQL:

```bash
systemctl stop mysqld
```

2. 设置MySQL环境选项

```bash
systemctl set-environment MYSQLD_OPTS="--skip-grant-tables"
```

3. 使用您刚才设置的选项启动MySQL

```bash
systemctl start mysqld
```

4. 以root身份登录

```bash
mysql -u root
```

5. 使用这些MySQL命令更新root用户密码

```bash
mysql> UPDATE mysql.user SET authentication_string = PASSWORD('MyNewPassword')
    -> WHERE User = 'root' AND Host = 'localhost';
mysql> FLUSH PRIVILEGES;
mysql> quit
```

6. 停止mysql

```bash
systemctl stop mysqld
```

7. 取消设置MySQL环境选项，以便下次启动

```bash
systemctl unset-environment MYSQLD_OPTS
```

8. 正常启动MySQL：

```bash
systemctl start mysqld
```

9. 尝试使用您的新密码登录：

```bash
mysql -u root -p
```

## 启动修改丢失的mysql单实例root密码方法

1. 首先停止mysql

```bash
sudo /etc/init.d/mysql stop

# 或者下面
sudo /usr/local/mysql/bin/mysql stop

# 或者 
service mysqld stop
```

2. 使用--skip-grant-tables启动mysql，忽略授权登录验证，服务不要停止，新开窗口做接下来的操作。

```bash
sudo mysqld_safe --skip-grant-tables --user=mysql # 提示：在启动时加--skip-grant-tables 参数，表示忽略授权验证
# 或者下面
sudo /usr/local/mysql/bin/mysqld_safe  --skip-grant-tables --user=mysql
```

3. 进入数据库系统

```bash
# 在终端中运行
mysql
```

4. 修改mysqlroot密码：update

```bash
# 终端进入MySQL数据中运行
mysql> update mysql.user set password=password("123456") where user='root' and host='localhost';
mysql> flush privileges;

# 终端中运行
mysqladmin -uroot -p123456 shutdown
```

5. 重新启动mysql

```bash
# 终端中运行
/etc/init.d/mysql start
mysql -uroot -p123456
```


## Mac下重置MySQL的root密码

以前的老版本root的默认密码为空，Mysql 5.6及以后版本出处于安全考虑，root密码已经不为空了。

```bash
# 表示没有生成root的临时密码
ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: NO)

# 表示生成了root的临时密码
ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: YES)
```

使用 `mysql -uroot -p` 登录进去。

1、停止 mysql server

在 Mac 中可以使用GUI停止 MySQL 服务，步骤：`系统偏好设置` > `MySQL` > `Stop MySQL Server`。您也可以使用命令行来停止服务，命令如下：

```bash
# Mac OS 里面可以这种方式
sudo /usr/local/mysql/support-files/mysql.server stop

# centos 停止mysql数据库
sudo /etc/init.d/mysqld stop 
```

2、终端，输入进入安全模式，运行之后进程保持挂载。

```bash
sudo /usr/local/mysql/bin/mysqld_safe --skip-grant-tables
```

3、新开终端，输入


```bash
sudo /usr/local/mysql/bin/mysql -u root
# 输入 Mac 系统用户密码后，
# 直接敲回车进入 mysql 终端，输入：
mysql> FLUSH PRIVILEGES;
mysql> ALTER USER 'root'@'localhost' IDENTIFIED BY 'MyNewPass';
# 输入 \q 退出 mysql 终端
\q
```

4、重启MySQL.

```bash
ps -ef | grep mysql
```

- 通过上面命令查看进程编号。  
- 通过`sudo kill 93`杀掉`mysql`进程  
- 启动服务`系统偏好设置` > `MySQL` > `Start MySQL Server`

命令行中更快捷的重启  

```bash
sudo /usr/local/mysql/support-files/mysql.server start
```


## 不重启mysqld修改密码的方法

1、首先得有一个可以拥有修改权限的mysql数据库账号，当前的mysql实例账号（较低权限的账号，比如可以修改test数据库）或者其他相同版本实例的账号。把data/mysql目录下面的user表相关的文件复制到data/test目录下面。

```
[root@localhost mysql]# cp mysql/user.* test/
[root@localhost mysql]# chown mysql.mysql test/user.*
```

2、使用另一个较低权限的账号链接数据库，设置test数据库中的user存储的密码数据。

```
[root@localhost mysql]# mysql -utest -p12345
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 17
Server version: 5.5.25a-log Source distribution

Copyright (c) 2000, 2011, 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> use test
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('yayun') where user='root';
Query OK, 0 rows affected (0.00 sec)
Rows matched: 5  Changed: 0  Warnings: 0

mysql>
```

3、把修改后的user.MYD和user.MYI复制到mysql目录下，记得备份之前的文件。

```bash
mv mysql/user.MYD mysql/user.MYD.bak
mv mysql/user.MYI mysql/user.MYI.bak
cp test/user.MY* mysql/
chown mysql.mysql mysql/user.*
```

4、查找mysql进程号，并且发送SIGHUP信号，重新加载权限表。

```
[root@localhost mysql]# pgrep -n mysql
2184
[root@localhost mysql]#
[root@localhost mysql]# kill -SIGHUP 2184
```

5、登陆测试

```bash
[root@localhost mysql]# mysql -uroot -pyayun
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 20
Server version: 5.5.25a-log Source distribution

Copyright (c) 2000, 2011, 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>
```

## 官网参考

- [How to Reset the Root Password](http://dev.mysql.com/doc/refman/5.7/en/resetting-permissions.html)