Solaris operating environment NIS supports password configuration files in both the Sun Operating Environment 4.x (Solaris release 1) password format and the Solaris Release 2 password and shadow file formats.
The mode of operation is determined by the existence of the file $PWDIR/shadow, where
$PWDIR is the Makefile macro set in the /var/yp/Makefile file. If the shadow file exists, NIS operates in the Solaris Release 2 mode. If this file does not exist, NIS operates in the SunOS 4.x mode.
In the SunOS 4.x mode, all password information is kept in the passwd file. In the Solaris Release 2 mode, password information is kept in the shadow file and the user account information is kept in the passwd file.
If the make macro
PWDIR is set to the /etc directory, NIS can operate only in the Solaris Release 2 mode because of the Solaris Release 2 passwd processing requirements. However, if
PWDIR points to any directory other than /etc, the user has the option of keeping passwd configuration files in either the SunOS 4.x format or in the Solaris Release 2 format. The rpc.yppasswdd daemon understands both password formats. The Solaris Release 2 format is recommended.