CentOS/RHEL Samba 3 AD member server setup

Although Samba 4 is attracting attention, Samba 3 still with a large user base. Many system/network administrators, like me, does not see a immediate advantage in upgrading. Samba 3 is mature and stable. Many needs to integrate theirs Samba infrastructure to Microsoft Active Directory. For them (and others as well), I wrote this post.