Description of problem: I enabled the attribute uniqueness plugin. Now, you cannot add another uid value. It fails with "ldap_add: Already exists". But you could do modrdn with delelteoldrdn=0, which allows the entry having multiple uid values even if the uniqueness plugin is on. I think this is a bug of attribute uniqueness plugin, which most likely does not prevent the add from some internal operation.
The report is based upon misunderstanding the attribute uniqueness plugin, which is supposed to enforce unique attribute values. dn: cn=attribute uniqueness,cn=plugins,cn=config nsslapd-pluginEnabled: on Having these 2 entries in DB: dn: uid=nuuser0,ou=newOU,dc=example,dc=com uid: uuser0 uid: uuser1 uid: nuuser0 givenName: new objectClass: top objectClass: person objectClass: organizationalPerson objectClass: inetorgperson sn: user0 cn: uniq user0 dn: uid=uuser2,ou=newOU,dc=example,dc=com uid: uuser2 givenName: new objectClass: top objectClass: person objectClass: organizationalPerson objectClass: inetorgperson sn: user2 cn: uniq user2 Modrdn the second entry to one of the UIDs in the first entry: dn: uid=uuser2,ou=newOU,dc=example,dc=com changetype: modrdn newrdn: uid=uuser0 deleteoldrdn: 0 modifying RDN of entry uid=uuser2,ou=newOU,dc=example,dc=com ldap_rename: Constraint violation ldap_rename: additional info: Another entry with the same attribute value already exists