MySQL用户及权限管理

一、 MySQL初始密码
新安装的MySQL默认是没有密码的，设置初始密码可以用以下命令

mysqladmin -u root password 'new-password'

mysqladmin -u root password 'password' -S /data/3306/mysql.sock #socket多实例

mysqladmin -u root password 'new-password'
mysqladmin -u root password 'password' -S /data/3306/mysql.sock #socket多实例

设置初始密码后，可在当前用户家目录下创建.my.cnf文件，配置好用户名和密码后，该用户可以免密码登录，要注意设置文件权限，不要让其他用户看到密码信息

vi ~/.my.cnf

[client]

user=root

host=localhost

password=cathy

vi ~/.my.cnf
[client]
user=root
host=localhost
password=cathy

MySQL服务器在读取配置文件的时候是按照以下顺序读取的：
/etc/my.cnf --> /etc/mysql/my.cnf --> $MYSQL_HOME/my.cnf --> --default-extra-file=/path/to/somefile--> ~/.my.cnf

如果不同配置文件有相同配置选项则以最后一个配置文件为准
二、修改root密码
方法一：命令行

mysqladmin -u root -p oldpassword password 'password' #单实例

mysqladmin -u root -p oldpassword password 'password'-S /data/3306/mysql.sock#多实例

mysqladmin -u root -p oldpassword password 'password' #单实例
mysqladmin -u root -p oldpassword password 'password'-S /data/3306/mysql.sock#多实例

方法二：登录mysql

mysql> update mysql.user set Password=password("storm") where User="root"

mysql> flush privileges

mysql> update mysql.user set Password=password("storm") where User="root"
mysql> flush privileges

此方法有风险，必须指定条件和password函数, 否则有可能会其他用户的密码一并改掉
方法三：

myslq> set password=password(456) # 修改当前登录用户密码

set password for 'storm'@'%' =password(456) # 修改指定用户密码

myslq> flush privileges

myslq> set password=password(456) # 修改当前登录用户密码
set password for 'storm'@'%' =password(456) # 修改指定用户密码
myslq> flush privileges

三、重置忘记的密码
1. 停止mysqld服务

/etc/init.d/mysqld stop

/etc/init.d/mysqld stop

2. 启动mysqld，忽略授权表



mysqld_safe --skip-grant-tables --skip-networking --user=mysql &

mysqld_safe --skip-grant-tables --skip-networking --user=mysql  &

--skip-grant-tables表示忽略授权表启动MySQL
--skip-networking表示不连入网络，防止无密码启动mysql带来安全隐患
3. 登录mysql修改密码

mysql

mysql> update mysql.user set Password=password("newpassword") where User="root"

mysql> flush privileges

mysql
mysql> update mysql.user set Password=password("newpassword") where User="root"
mysql> flush privileges

注意：二进制包安装MySQL，在执行mysqld_safe --skip-grant-tables命令时会出现如下错误：

[root@dev ~]# mysqld_safe

160419 20:32:08 mysqld_safe Logging to '/usr/local/mysql/data/dev.err'.

touch: cannot touch `/usr/local/mysql/data/dev.err': No such file or directory

chmod: cannot access `/usr/local/mysql/data/dev.err': No such file or directory

touch: cannot touch `/usr/local/mysql/data/dev.err': No such file or directory

chown: cannot access `/usr/local/mysql/data/dev.err': No such file or directory

160419 20:32:08 mysqld_safe The file /usr/local/mysql/bin/mysqld

does not exist or is not executable. Please cd to the mysql installation

directory and restart this script from there as follows:

./bin/mysqld_safe&

See http://dev.mysql.com/doc/mysql/en/mysqld-safe.html for more information

/application/mysql/bin/mysqld_safe: line 128: /usr/local/mysql/data/dev.err: No such file or directory

[root@dev ~]# mysqld_safe
160419 20:32:08 mysqld_safe Logging to '/usr/local/mysql/data/dev.err'.
touch: cannot touch `/usr/local/mysql/data/dev.err': No such file or directory
chmod: cannot access `/usr/local/mysql/data/dev.err': No such file or directory
touch: cannot touch `/usr/local/mysql/data/dev.err': No such file or directory
chown: cannot access `/usr/local/mysql/data/dev.err': No such file or directory
160419 20:32:08 mysqld_safe The file /usr/local/mysql/bin/mysqld
does not exist or is not executable. Please cd to the mysql installation
directory and restart this script from there as follows:
./bin/mysqld_safe&
See http://dev.mysql.com/doc/mysql/en/mysqld-safe.html for more information
/application/mysql/bin/mysqld_safe: line 128: /usr/local/mysql/data/dev.err: No such file or directory

错误原因暂时未找到，但是仔细看报错信息：Please cd to the mysql installation directory and restart this script from there as follows: ./bin/mysqld_safe&
意思是要进入MySQL的安装目录再执行mysqld_safe命令，我尝试进入我安装的MySQL目录：/application/mysql/bin/然后执行mysqld_safe依然报错，最后发现只有在MySQL的安装目录下执行./bin/mydqld_safe才能正常执行，具体原因还有待查找！

4. 重启mysql

/etc/init.d/mysqld stop

/etc/init.d/mysqld start

/etc/init.d/mysqld stop
/etc/init.d/mysqld start

若修改完密码后无法关闭，用mysqladmin -uroot -pnewpassword shutdown关闭
多实例MySQL启动修改丢失的root密码

mysqld_safe --defaults-file=/data/3306/my.cnf --skip-grant-tables&

mysql -uroot -p -S /data/3306/mysql.sock # 登录时用空密码

mysqld_safe --defaults-file=/data/3306/my.cnf --skip-grant-tables&
mysql -uroot -p -S /data/3306/mysql.sock  # 登录时用空密码

四、创建用户及授权
方法一：先创建用户再授权

mysql> create user 'storm'@'localhost' IDENTIFIED BY 'mypass';

mysql> grant all on db1.* to 'jeffrey'@'localhost';

mysql> create user 'storm'@'localhost' IDENTIFIED BY 'mypass';
mysql> grant all on db1.* to 'jeffrey'@'localhost';

方法二：直接授权给用户，用户不存在时则创建

mysql> grant all on dbname.* to 'jeffrey'@'localhost' identified by 'password'

mysql> grant all on dbname.* to 'jeffrey'@'localhost' identified by 'password'

1. 用户名格式

MySQL创建用户时，用户名的格式为：'用户名'@'主机' ，其中用户名和主机名的引号可用单引号，也可用双引号，但是不可省略。主机权限范围例举如下：
‘storm'@'%'
#表示所有主机均可使用storm账户登录
mysql ‘storm'@'192.168.0.%
#表示只允许192.168.0网段的用户连接，这种情况即使本地连接mysql，也需要指定-h IP的方式连接
mysql‘storm'@'localhost’
#表示只允许本地连接
2. MySQL用户权限
MySQL可授权的权限有：SELECT, UPDATE, DELETE, CREATE, DROP, RELOAD, SHUTDOWN, PROCESS,FILE, REFERENCES, INDEX, ALTER, SHOW DATABASES, SUPER, CREATE TEMPORARY TABLES,LOCK TABLES, EXECUTE, REPLICATION SLAVE, REPLICATION CLIENT, CREATE VIEW, SHOWVIEW, CREATE ROUTINE, ALTER ROUTINE, CREATE USER, EVENT, TRIGGER， all表示所有权限。
为用户授权时，可精确到数据库、数据库所对应的表、表里的某个字段的具体权限，如：
grant all on *.* to ‘storm'@'%'
#为storm授予所有库的所有操作权限
grant all on school.* to ‘storm'@'%'
#为storm授予school数据库下的所有表的所有操作权限

grant select, insert,update on school.class to ‘storm'@'%'
#为storm授予school数据库下class表的 select, insert,update权限

grant update(age) on on school.class to ‘storm'@'%'
#表示storm用户只能update的字段为age
3. 查看用户权限

mysql> show grants for storm@'%';

mysql> show grants for storm@'%';

4. 撤回用户权限

REVOKE ALL PRIVILEGES, GRANT OPTION FROM user [, user] ...

REVOKE ALL PRIVILEGES, GRANT OPTION FROM user [, user] ...

5. 删除用户
mysql> drop user 'root'@'127.0.0.1';