登入提示 Your password has expired！(root enforced)

連有root許可權的使用者也要改，但是輸入新密碼總是提示 Bad password: is too simple.

怎麼輸入新密碼都提示這個 ===》》》 解決辦法：密碼還不夠複雜！用這個：9#kwT7rhSX^mQ&@I 作為新密碼登入具有root許可權的使用者，再使用下面的命令更改為簡單些的密碼

$ sudo passwd user-name　　　　# 仍會提示祕密too simple，但是能成功修改

深層次原因：

1） /etc/pam.d/common-password 中有一句下面這樣的命令

password [success=2 default=ignore]  pam_unix.so obscure use_authtok try_first_pass sha512

改為

password [success=1 default=ignore]  pam_unix.so minlen=1 sha512

（改完後好像要重啟還是怎麼的才能生效，類似於source .bashrc這種操作，暫時沒找到怎麼做）

其中obscure會進行額外的密碼健壯性檢查，用$ man pam_unix可以檢視，包括

 obscure
           Enable some extra checks on password strength. These checks are based on the 
 
"obscure" checks in
           the original shadow package. The behavior is similar to the pam_cracklib module, but for
           non-dictionary-based checks. The following checks are implemented:

           Palindrome
               Verifies that the new password is not a palindrome of (i.e., the reverse of) the previous one.

           Case Change Only
               Verifies that the new password isn
 
't the same as the old one with a change of case.

           Similar
               Verifies that the new password isn't too much like the previous one.

           Simple
               Is the new password too simple? This is based on the length of the password and the number of
               different types of characters (alpha, numeric, etc.) used.

           Rotated
               Is the new password a rotated version of the old password? (E.g., "billy" and "illyb")

可以看到，simple提示就是說明需要字元、數字等在密碼內，密碼足夠複雜才能通過檢查。

2）針對密碼到期的問題，可以使用下面的命令檢視和修改密碼的有效期

$ chage -l user-name　　　　　　# 檢視密碼有效期
$ chage -M -1 user-name　　　　# 修改最長有效期為 -1