Who is the Diri from the story, Kaddish for a Child Not Born?

The Diri is the director of the boarding school that the narrator attends from age five to ten. He is a short man with a large belly, yellowish-white mustache, and long white hair. His students call him the Plug behind his back. The Diri controls the school with strict authority and fear. He is rarely seen by the students except during the occasional outburst of misbehavior and at Saturday afternoon rapports. The Diri is ultimately killed in the Nazi concentration camp gas chambers during the Holocaust.