mysql-community-server安装完后不知道root密码

修改方法：

service mysqld stop
mysqld_safe --skip-grant-tables &
mysql -u root
use mysql;
update user set authentication_string=password('1111') where user='root';
flush privileges;
quit
service mysqld restart
或者用  /etc/init.d/mysql start启动
 
启动后用命令建数据库是还是会提示需要新设置密码 ERROR 1820 (HY000): You must reset your password using ALTER USER statement before executing this statement.
 
用：SET PASSWORD = PASSWORD('123456') 设置密码时又提示：ERROR 1819 (HY000): Your password does not satisfy the current policy requirements
 
原因是密码验证规则问题，用 set global validate_password_policy=0;  修改后成只验证长度，再执行：

SET PASSWORD = PASSWORD('123456') 就成功了。