Given an existing LDAP server used for authentication, can Windows desktops authenticate users against LDAP or perhaps Kerberos?
I once tested this succesfully with pGina, but it's not very friendly to setup.
You can also use a SAMBA server acting as an Active Directory provider, with an LDAP backend, but I haven't tested this yet. Here are the two basic steps do:
SAMBA as a PDC
The basic configuration goes like this:
[global] passdb backend = tdbsam os level = 33 preferred master = auto domain master = yes local master = yes security = user domain logons = yes logon path = \\%N\profiles\%U logon drive = H: logon home = \\homeserver\%U\winprofile logon script = logon.cmd [netlogon] path = /var/lib/samba/netlogon read only = yes [profiles] path = /var/lib/samba/profiles read only = no create mask = 0600 directory mask = 0700
More info on the SAMBA docs.
Properly configuring an LDAP server is not something trivial (neither the SAMBA server IMHO), but after you configure one (OpenLDAP, FDS, etc.), here's some good info on how to integrate it with SAMBA. And more specific for RedHat.
I also hear SAMBA 4 will be a complete replacement for Active Directory, but who knows when that will be released.
Anyway, I don't know if this has become easier than when I tried it (about 2 years ago), but I hope so, because I gave up after a few weeks of trial... Maybe it's time to give it another go.
Back then, my personal preference was for FDS because it has a great admin console, and it was easier to set up.
Edit: I just remembered eBox. I haven't tested it because I don't like all-in-one solutions, but take a look at the site if you do (it offers plenty more than a domain controller).
Not without a custom logon provider (msgina replacement)...
Best bet is to either set up a Windows domain controller for Windows clients to log on to (will enable you to utilize group policies and other useful stuff) and have it sync with your existing LDAP service (check out Services for Unix). Or use samba and have it use your LDAP directory for authentication.