[Fedora-directory-users] NSUniqueID

[Richard Megginson]

Bjorn Oglefjorn wrote:
> On 5/15/07, *Richard Megginson* <rmeggins at redhat.com 
> <mailto:rmeggins at redhat.com>> wrote:
>
>     Bjorn Oglefjorn wrote:
>     > That's the problem Richard, I'm not sure how it happens.  I can tell
>     > you this much though.  I am using NSUniqueID as a globally unique id
>     > for a one-way sync agreement to a specific application (from FDS to
>     > the application).  The requirement for the globally unique id is
>     that
>     > it never changes.  If it somehow does change, the sync process
>     > provides an error stating that the globally unique ids in FDS
>     and the
>     > application no longer match.  I can't determine exactly what is
>     > causing this change, but I do know that it is happening.
>     But how does the sync process/application determine that the unique ID
>     has changed?  And is it possible that some application is writing
>     to the
>     nsUniqueID attribute and changing its value externally?  Are you using
>     replication?
>
>
> There is no application that has write access to our LDAP user tree.  
> I am using a dual multi-master replication setup.  What about 
> replication would cause the NSUniqueID to change?
If you delete an entry then add it back with the same DN and mail value, 
it will generate a new nsUniqueID for the new entry.  Also, certain 
replication operations may generate replication conflict entries.  In 
this case, you could see two entries with the same mail attribute but 
different nsUniqueID values and different DNs.

To check for this, do a search for each of the "duplicate" nsUniqueID 
values using a search filter like this:
(|(nsuniqueid=value1)(objectclass=nsTombstone))
and
(|(nsuniqueid=value2)(objectclass=nsTombstone))
>
>     For example, does your sync app do something like this:
>     get entry by name e.g . (uid=somename).  Store the nsUniqueID for
>     the entry.
>     Then later, do the same search (uid=somename) and get the nsUniqueID.
>     Compare the nsUniqueID to the one stored previously.
>
>
> That is nearly exactly how the sync application works.  For any entry 
> that the application keeps track of, it keeps a 'lastseen' LDIF.  on 
> the next run of the sync, a search is performed and the LDIFs are 
> compared.
>
>     If this is the case, is it possible that the uid for the entry has
>     changed?
>
>
> No, the only change made to the entry in question was to the 'mail' 
> attribute.
>
>     > --BO
>     >
>     > On 5/15/07, *Richard Megginson* <rmeggins at redhat.com
>     <mailto:rmeggins at redhat.com>
>     > <mailto:rmeggins at redhat.com <mailto:rmeggins at redhat.com>>> wrote:
>     >
>     >     Bjorn Oglefjorn wrote:
>     >     > Hello all,
>     >     >
>     >     > Can someone tell me, does the NSUniqueID attribute ever
>     change for a
>     >     > given entry in the directory?
>     >     No.
>     >     > If so (I've seen it happen),
>     >     Can you describe exactly what you saw and how to reproduce it?
>     >     > what are the criteria that prompt NSUniqeID to change?
>     >     >
>     >     > Thanks,
>     >     > BO
>     >     >
>     >    
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