Two (or more) KDCs and a single LDAP directory

Simo Sorce ssorce at
Tue Jul 15 14:48:07 EDT 2008

On Tue, 2008-07-15 at 12:21 -0300, Klaus Heinrich Kiwi wrote:
> Hi,
>  I'd like to know what are the supported methods of usage if I have to
> use two or more KDC instances with one LDAP directory. I can see a
> couple of scenarios but I'm not really sure what is the supported way of
> dealing with them. For example:
> 1) Two KDC servers, one LDAP server, same realm:
>    Since LDAP has no locking mechanism, would there be potential race
> conditions? Is kpropd the correct way of doing this?

Internal locking guarantees operations are atomic. So, if the ldap
client is written correctly, data should always be consistent.

> 2) Two KDC servers, one LDAP server, separate realms:
>    I don't see why I couldn't have two KDC instances using the same LDAP
> server, if they are not dealing with the same realm.

As long as you have 2 separate parts of the tree dedicated to the 2
realms, there should be no problem.

> 3) one KDC server, two mirror LDAP servers, same realm:
>    The way I see we would need LDAP synchronization between the LDAP
> servers

Using native LDAP replication is usually the way to go.

> 4) two KDC servers, two mirror LDAP servers, same realm:
>    We should use kpropd + ldap synchronization?

I don't know what kpropd would buy you, the data is already replicated
by ldap.

> 5) two KDC servers, two mirror LDAP servers, separate realms:
>    same as (2)?



Simo Sorce * Red Hat, Inc * New York

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