This document is a step by step guide for configuring Ubuntu 7.10 as a Samba Domain Controller with an LDAP backend (OpenLDAP). The point is to configure a server that can be comparable, from a central authentication point of view, to a Windows Server 2003 Domain Controller. The end result will be a server with an LDAP directory for storing user, group, and computer accounts. A Windows XP Professional SP2 workstation will be able to join the domain once properly configured.
Please note that you do not have a fully comparable Windows domain controller at this time. Do not kid yourself, this guide only gets you a server with LDAP authentication. Of course this can be expanded to include slave servers to spread out authentication over multiple networks. Please also note that it took me approximately two and a half weeks to compile this information and get it working. The same functionality can be had in Windows in less than four hours (and this includes operating system installation). In my humble opinion the open source community will need to work on this side of Linux in order for it to be a true alternative to Windows.