今天在CentOS 6.5上安装mysql5.7时遇到一个问题，没有初始化密码。
在mysql5.7之前的版本首次登陆是无需密码的，但是5.7起会生成一个初始化密码/root/.mysql_secert
cat /root/.mysql_secert 就可以查看初始化密码了
但是我的安装没有发现.mysql_secert文件。
这种情况的解决方案:
mysqld_safe --user=mysql --skip-grant-tables &
mysql -uroot -p
>use mysql;
>desc user;
...略
| authentication_string | text | YES | | NULL | |
| password_expired | enum('N','Y') | NO | | N | |
| password_last_changed | timestamp | YES | | NULL | |
| password_lifetime | smallint(5) unsigned | YES | | NULL | |
| account_locked | enum('N','Y') | NO | | N | |
+------------------------+-----------------------------------+------+-----+-----------------------+-------+
>select user,host,authentication_string,password_expired from user;
+-----------+-----------+-------------------------------------------+------------------+
| user | host | authentication_string | password_expired |
+-----------+-----------+-------------------------------------------+------------------+
| root | localhost | *9AA01F6E2A80A823ACB72CC07337E2911404B5B8 | Y |
| mysql.sys | localhost | *THISISNOTAVALIDPASSWORDTHATCANBEUSEDHERE | N |
+-----------+-----------+-------------------------------------------+------------------+
>update user set authentication_string=password('123456') where user='root';
>flush privileges;
重新登录mysql，首先停掉所有mysql进程
mysqld_safe --user=mysql &
mysql -uroot -p
>show databases;
ERROR 1820 (HY000): You must reset your password using ALTER USER statement before executing this statement.
> alter user root@'localhost' identified by 'aolens123..';
＃这下就好了
可以看到5.7的密码字段改成了authentication_string，