But come to think of it, slapd will start fine if existing entires
a "MUST" attribute. It doesn't read the entire database to check, after
all. Maybe something will misbehave when trying to access such entries,
I don't know. But maybe it'll work fine to restart the server with the
MUST and add the actual attribute afterwards.
Any attempt to modify non-schema compliant entries that are already in the
database will fail unless the modification makes them schema compliant
(namely, the modification adds the missing required attribute). Comes to
mind that something like a schema compliance checking tool, either off- or
on-line could be useful. Sort of a "slapschema" that checks the schema
compliance of each entry (matching a filter or within a subtree
specification) in a given database.