OpenDirectory is a feature included with Mac OS X Server. Wouldn’t it be nice if you could use it without having to spend hundreds of dollars on a server license? Wouldn’t it be great if you could add it into your existing Linux-based OpenLDAP server? It’s actually quite easy because OpenDirectory is a standard OpenLDAP server with a special Apple schema.

0. Prerequisites
– OpenLDAP server with Samba integration (I’m runnig it on a Ubuntu 8.04 server, using the standard OpenLDAP and Samba packages). I won’t go into the details of how to set this up, there are lots of tutorials around the web on this.
– some kind of LDAP admin tool, I used phpLDAPAdmin
– Mac OS X 10.5 Leopard clients

1. Adding the Apple schema to your OpenDirectory server
It is located in /etc/openldap/schema/apple.schema on any Mac. Copy this file to your OpenLDAP server and add it to your slapd.conf.
You may run into the problem that apple.schema references some samba.schema entries that were deprecated with Samba 3. Specifically, these are acctFlags, pwdLastSet, logonTime, logoffTime, kickoffTime, homeDrive, scriptPath, profilePath, userWorkstations, smbHome, rid and primaryGroupID, so you’ll need to editapple.schema and replace these with their Samba 3 counterparts.
Now, restart the OpenLDAP daemon so it recognizes the changes.

2. Adding some Mac-specific attributes to your LDAP server
Add an ou=macosx branch to your LDAP tree, under which you’ll need to create ou=accesscontrols, ou=augments, ou=automountMap, ou=autoserversetup, ou=certificateauthorities, ou=computer_groups, ou=computer_lists, ou=computers, ou=filemakerservers, ou=locations, ou=machines, ou=maps, ou=mount, ou=neighborhoods, ou=places, ou=preset_computer_groups, ou=preset_computer_lists, ou=preset_computers, ou=preset_groups, ou=preset_users, ou=printers, and ou=resources.
To all your LDAP groups, add the apple-group objectClass. To all your LDAP users, add the apple-user objectClass.

3. Connecting your Mac to the LDAP directory
On your Mac, go into Directory Access and add your LDAP server. Choose OpenDirectory as the server type and adjust the Samba mappings to match your changes from step 1. Here is a plist you can import into Directory Access that already has these mappings corrected: LDAPv3_Unix_Samba3_OD.plist.
If you want your other clients to automatically use this mapping, create a cn=config branch in your LDAP tree and use the Write to Server button in Directory Access.

4. Use Workgroup Manager to set network home folders, managed preferences, …
Now, you can use Workgroup Manager to manage network home folders and managed preferences, just like you would on a Mac server.  You’ll need to authenticate using an LDAP user who has full write privileges to the directory (as set in slapd.conf). The standard cn=admin,dc=example,dc=com user will NOT work.

5. Conclusion
Almost everything works, except for:
– adding new users and group through Workgroup Manager
– solution: unknown
– assigning directory admin privileges to users through Workgroup Manager
– solution: using an OpenLDAP server set up to use cn=config instead of slapd.conf. This will also require going into Directory Access again and adding the OLCBDBConfig, OLCFrontEndConfig, OCGlobalConfig, OLCSchemaConfig and OLCOverlayDynamicID record types back in (they are included in the OpenDirectory mapping, but I deleted them from mine because they only cause error messages on an OpenLDAP server with slapd.conf configuration).

Here are all the web sites that helped me in the process of figuring this out:
http://docs.info.apple.com/article.html?path=ServerAdmin/10.4/en/c6od15.html (this one is especially important because it explains what to do if your LDAP server is not set up for SASL authentication)
http://www.emmes-world.de/mac-afp-homes.html (this one describes a similar setup and was my most important resource)
http://rajeev.name/blog/2006/09/09/integrating-mac-os-x-into-unix-ldap-environment-with-nfs-home-directories/
http://www.netmojo.ca/blog/tag/ldap/
http://www.macdevcenter.com/pub/a/mac/2003/08/26/active_directory.html?page=2

7. Further Information
Since you’re not using Kerberos for authentication, you may want to look at securing your LDAP connections with SSL. Here are some links that talk about it:
http://www.novell.com/coolsolutions/feature/19965.html
http://www.afp548.com/article.php?story=20071203011158936

Someone else also wrote a blog post about Setting up a Linux server for OS X clients, in which they also describe how to incorporate Kerberos into the whole equation. That’s certainly something worth considering.