shadow

в /etc/shadow?

~> man shadow

       The password field must be filled.  The encryped password  consists  of
       13  to 24 characters from the 64 character alphabet a thru z, A thru Z,
       0 thru 9, . and /.  Refer to crypt(3) for details on how this string is
       interpreted.   If  the  password field contains some string that is not
       valid result of crypt(3), for instance ! or *, the  user  will  not  be
       able to use a unix password to log in, subject to pam(7).