Caution: It is difficult to change this decision after you run setup.
Hmmm. I'm not sure what drove us to make this statement in the documentation, as making this transition is actually quite simple and straightforward. I *think* that it might have been the fact that CIFS has to be stopped and restarted to move from workgroup mode into domain mode (or vice versa), thus temporarily and briefly disrupting file service to Windows clients. However, if you can arrange to make the transition at a time of low usage (the small hours of the morning for example), the disruption should have minimal impact. The whole operation should take just a few minutes. You need to execute a "cifs terminate" followed by another "cifs setup" and then you're basically done.
<gulp> Okay, I do want to change (from a workgroup to a domain).
Good move! :-)
How difficult is "difficult"?
As I mentioned, not very (aside from the brief service disruption).
How does changing the authentication method from NIS to a domain controller affect the UNIX boxes accessing the filer via NFS?
It doesn't. However, if you do start creating NTFS or MIXED mode file systems after making the transition, you may need to take a look at how UNIX security is effected by the use of these modes. There are two papers in the "Technology" section of our web site that explain these issues quite well. If you stick with UNIX mode file systems however, you have absolutely no reason to be concerned about how the new domain mode of CIFS effects NFS, because it doesn't.
Keith