pam_unix禁用密码强度检查

/etc/pam.d/common-password

man pam_unix

minlen=n
      Set a minimum password length of n characters. The default value is
      6. The maximum for DES crypt-based passwords is 8 characters.

  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.

改成如下：
password [success=1 default=ignore] pam_unix.so minlen=1 sha512
可禁用密码强度检查