[Freeipa-users] New FreeIPA Install; Testing for Proof of Concept

[Simo Sorce]

On Wed, 2012-08-08 at 19:59 +0200, Petr Spacek wrote:
> On 08/08/2012 07:27 PM, Rob Ogilvie wrote:
> > On Wed, Aug 8, 2012 at 9:06 AM, Petr Spacek <pspacek at redhat.com> wrote:
> >> Best way is to create subdomain UNIX.MYCOMPANY.COM and fill it with proper
> >> SRV records (or let IPA to manage it).
> >
> > Ugh, I hope this doesn't end up pushing us back to NIS.
> >
> > If I can get our infrastructure guys to buy off on making a
> > unix.mycompany.com subdomain in DNS, would I need to move all the
> > hosts to be under that subdomain in DNS?  I have some services
> 
> Definitely not. You can create subdomain UNIX.MYCOMPANY.COM, fill it with SRV 
> records and leave this subdomain without hosts (maybe except IPA servers ...). 
> It is not necessary to rename all hosts.
> 
> Problem is simple - Kerberos libraries have to know where KDCs are located - 
> and DNS is standardized way how to accomplish it.
> 
> Let me quote another reply from this thread:
> On 08/08/2012 06:14 PM, KodaK wrote:
>  > You*could*  use something like puppet to manage your krb5.conf files
>  > (I have to with our AIX machines.)
>  >
>  > Also, it's important to note that your REALM does NOT need to match
>  > your dns domain name
>  > It's a convenience, and it's very, very helpful to do so, but it is
>  > possible to have a REALM called
>  > "MIDDLEEARTH" if you wanted.  I'm not sure how IPA would deal with
>  > that, but I know you
>  > can do it in straight up Kerberos.
> 
> 
> > configured that are difficult to rename the DNS domain of.  Could, for
> > instance, host-one.mycompany.com be part of the UNIX.MYCOMPANY.COM
> > realm, given a MYCOMPANY.COM realm also exists?
> 
> Yes, it could.
> 
> >
> > I could then put some SRV records into the subdomain's zone to point
> > the kerberos stuff to the IPA server, change the domain on the IPA
> > server, change the realm on the IPA server, re-register clients, and
> > everything would be happy?
> 
> I get lost in the renaming part. Can you describe your idea in bigger detail?
> 
> >
> > Ugh... actually... now that I think about this, I don't think I want
> > half my servers in a unix subdomain in DNS, which means DNS and realm
> > wouldn't match...
> >
> > Thoughts?  Aside from rebuilding the infrastructure I've built already?  :-)
> 
> Let all machines in MYCOMPANY.COM and use IPA realm UNIX.MYCOMPANY.COM.
> IMHO it is simplest way.
> 
> 
> This limitation comes from Kerberos: You are trying to use *single domain 
> name* for *two independent Kerberos realms* - it is principally not possible.

I just need to pint one one problem with leaving all machines under
MYDOMAIN.COM, and that is if you later want to make a trust (option
available starting from ipa 3.0) between the AD realm and the IPA realm,
the machines in the mydomain.com domain will not be able to be accessed
by the users of the AD realm. That is because the machines joined to the
AD realm will think that the mydomain.com machines are always served up
by the AD domain.

On the IPA side you amy also have so issues as you will not be able to
tell IPA clients that they need to ask the AD KDC for the hosts under
mydomain.com

So ultimately, I would put as many machines as you can under
UNIX.MYDOMAIN.COM, to minimize confusion in case later on you want to
establish a trust between the AD domain and the IPA domain.

Simo.

-- 
Simo Sorce * Red Hat, Inc * New York