Re: Question regarding Combining ObjectClasses to add attributes

[Rich Megginson <rmeggins@xxxxxxxxxx>]

On 07/09/2012 09:44 AM, Anderson, Cary@CIO wrote:

I have recently started working with the Director Server, and I have read the documents for both 389 and RHDS, but I am having some difficulties regarding ObjectClass types, and combining them in order to extend the available attributes for an object.  The documents indicate that you can only have one Structural ObjectClass and multiple Aux. ObjectClasses, and I'm a bit hazy on the rules for Abstract ObjectClasses.  

If I take the example of needing to add the "host" attribute to a user object.  A RHN knowledgebase article indicates to add the "hostobject" ObjectClass rather than the "Account" ObjectClass.

Can you provide a link to this kbase article?

My assumption was that "hostobject" was an Aux. ObjectClass, and that "Account" was Structural, but when I look at the two ObjectClasses via the administrative GUI, they both have "Top" listed as the parent ObjectClass.  So I'm not certain why one is appropriate and the other is not.

It would appear the console does not tell you if the objectclass is structural, auxiliary, or abstract.  You cannot tell by just the inheritance - by default, all objectclasses have "top" as the superior unless otherwise specified.

This is the official LDAPv3 description - http://www.ietf.org/rfc/rfc4512.txt

An entry may have only one STRUCTURAL objectclass, and multiple AUXILIARY objectclasses.  Chances are you will want to use AUXILIARY objectclasses for your extra attributes (like posixAccount) and just use one of the pre-defined objectclasses (like inetOrgPerson) as your STRUCTURAL objectclass.

Moving forward I want to be able to combine ObjectClasses to extend available objects without introducing data integrity issues in my ldap directory.  I am looking for some clarification of rules regarding structural objectclasses,

See rfc4512

and if there is an easy way via the admin gui to tell the difference between structural, auxillary, and abstract objectclasses.

No.  You'll have to search cn=schema to check:
ldapsearch -xLLL -s base -b "cn=schema" "objectclass=*" objectclasses | perl -p0e 's/\n //g' | grep AUXILIARY

Note that ldapsearch wraps the output, so you'll have to use perl (or sed) to unwrap - see http://richmegginson.livejournal.com/18726.html

Also will the directory do some sort of intregrity checking if you attempt to combine improper objectclasses either via commandline or the admin gui?

Yes, although by default 389 will allow an entry to have multiple structural objectclasses, but that will change in a future release, so don't rely on that behavior.

 

Thanks

 

 

           Cary Anderson

              916.464.5108

Linux Support | Engineering Dept.

 

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