On 08/12/2012 12:05 PM, Simo Sorce wrote:



----- Original Message -----
On 08/08/2012 08:07 PM, Simo Sorce wrote:
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 <pspa...@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.

Is possible to workaround these problems with hostname-realm
mappings?

It is not clear solution, I know, but it should be doable for limited
set of
unix machines.
AFAIK Windows AD (I tested it with 2008 R2) has ability to set
hostname-realm
mappings through Group policy.

Yes from the Linux side it is possible to map single hostnames to a realm, so 
the top domain could be generally mapped to the AD realm, and then single hosts 
mapped to the IPA realm. This is not possible for windows machines in the AD 
domain though (afaik).

Simo.

It should be doable via AD Group Policy:
http://support.microsoft.com/kb/947706/en-us

Petr^2 Spacek

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