Linux version 2.6.9-34:where are the old passwords stored?

["liuruihong" <liuruihong baidu com>]

/etc/pam.d/passwd

password required pam_cracklib.so retry=3 type=liuruihong dcredit=-3

password required pam_unix.so use_authtok

 

I want to know where the old passwd of normal account passwords stored,I find the /etc/security/opasswd file is null.