最近在centOS 7上，通过yum安装了mysql，安装成功后，使用root登录，出现了如下报错：

ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: NO)

mysql版本为：Ver 14.14 Distrib 5.7.10, for Linux(X86_64) using EditLine wrapper

然而实际上并没有进行过root密码设置(不知道是不是安装过程有被忽略的地方？)。

对此就各种寻找答案，大致有下面一些情况：

1. 有说root的随机密码位于/root/.mysql_secret中，但是我根本没有/root/.mysql_secret文件。有文章表示

   > ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using
   > password: NO) :表示没有生成root的临时密码
   > 
   > ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using
   > password: YES) :表示生成了root的临时密码。

2. 有些资料说root的默认密码为空，经过确认那是以前的老版本，Mysql 5.6及以后版本出处于安全考虑，root密码已经不为空了。

最终找到对我来说有用的解决方案。

产生原因：

Now that the password MySQL had generated is expired, the problem is reduced to getting this password to work again (1) or generate a new one (2). This can be accomplished by running MySQL with the skip-grant-tables option which would make it ignore the access rights:

解决方法：

1. Stop your MySQL server.

2. Add skip-grant-tables at the end of the [mysqld] section of my.cnf file and save it.

3. Start MySQL server.

4. In terminal, typemysql -u root -pto get into MySQL command prompt.

5. In the command prompt, typeUSE mysql;to get into the mysql database where it keeps database users.

6. Type

   UPDATE user SET password_expired = 'N' WHERE User = 'root'; 

   to let MySQL know the password is not expired (1) or

   UPDATE user SET authentication_string = PASSWORD('YourNewPassword'), password_expired = 'N' WHERE User = 'root';

附上链接：Unable to access MySQL after it automatically generated a temporary password

发布出来，供大家参考。