phpMyAdmin 不能進入的問題 – 走過的、學過的、看過的

更新 mysql 版本以後，尤其是從 4.0.x 到 4.1.x，發生 phpMyAdmin 有以下的問題：

如果 root 密碼是空的，可以登入。
如果 root 密碼改了以後，不是空的，無法登入，且有以下的訊息
#1251 - Client does not support authentication protocol requested by server; consider upgrading MySQL client

原因是因為 mysql 4.1.x 以後，可能是因為安全性的理由，密碼的演算法更新了，這個演算法，只能在 4.1.x 以後的版本以及新的 client 端可以用。

Client does not support authentication protocol requested by server; consider upgrading MySQL client.

To solve this problem, you should use one of the following approaches:

Upgrade all client programs to use a 4.1.1 or newer client library.
When connecting to the server with a pre-4.1 client program, use an account that still has a pre-4.1-style password.
Reset the password to pre-4.1 style for each user that needs to use a pre-4.1 client program. This can be done using the SET PASSWORD statement and the OLD_PASSWORD() function:mysql> SET PASSWORD FOR
-> 'some_user'@'some_host' = OLD_PASSWORD('newpwd');

Alternatively, use UPDATE and FLUSH PRIVILEGES:

mysql> UPDATE mysql.user SET Password = OLD_PASSWORD('newpwd')
-> WHERE Host = 'some_host' AND User = 'some_user'; mysql> FLUSH PRIVILEGES;

Substitute the password you want to use for “newpwd” in the preceding examples. MySQL cannot tell you what the original password was, so you'll need to pick a new one.

Start mysqld with the --old-passwords option.
Assign an old-format password to each account that has had its password updated to the longer 4.1 format. You can identify these accounts with the following query:mysql> SELECT Host, User, Password FROM mysql.user
-> WHERE LENGTH(Password) > 16;

For each account record displayed by the query, use the Host and User values and assign a password using the OLD_PASSWORD() function and either SET PASSWORD or UPDATE, as described earlier.

以上的情形，在 Win32s 底下最常發生，解決方式以是在 MySQL Command Line Client 打入密碼登入後，執行以下指令最快：

SET PASSWORD FOR root@localhost = OLD_PASSWORD('passwd');

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