10月8号
A MySQL Server has been running an existing application successfully for six months. The
my.cnf is adjusted to contain this additional configuration:
The MySQL Server is restarted without error.
What effect will the new configuration have on existing account?
[mysqld]
default-authentication-plgin=sha256_password
A. They will have to change their password the next time they login to the server.
B. They are not affected by this configuration change.
C. They will have their passwords updated on start-up to sha256_password format.
D. They all connect via the secure sha256_password algorithm without any configuration change.
解析:
默认身份认证插件。可接受的值 mysql_native_password（使用MySQL本地密码）和sha256_password（用SHA-256 密码）关于这些插件见Section 6.3.7.1, “The Native Authentication Plugins”，和 Section 6.3.7.2, “The SHA-256 Authentication Plugin”。这个选项在MySQL5.6.6新增。
该选项的值影响服务操作的几个方面：
1）对于没有明确指名插件，决定哪个插件分配到新用户。
2）在启动时设置系统变量 old_passwords 的值和默认插件所需的密码散列格式发生冲突。这结果影响 PASSWORD() 函数使用的密码散列方法。
3）下面任何创建新账号的语句，服务器将使用默认验证插关联帐户和分配指定的密码给帐户，该哈希值是old_passwords的值。CREATE USER ... IDENTIFIED BY 'cleartext password';
GRANT ... IDENTIFIED BY 'cleartext password';
所以这种情况对老用户没有影响,选择B