A person who holds open the door at the entryway (entrance) to a building, summons taxicabs, and provides an element of security; in apartment buildings, he also accepts deliveries and may perform certain concierge type services.
A doorman.
Someone who looks after the maintenance and cleaning of a public building.
A caretaker or custodian; someone who maintains a school building specifically and may serve other administrative roles.
A moderator for a discussion forum.