Postmaster
Also called: postmaster process, supervisor process, parent postgres process
The postmaster is the supervisor process that starts a PostgreSQL server. It creates the shared memory segment, opens the listening socket, forks a dedicated backend for each client connection, launches the background worker processes, and monitors all its children. Every other PostgreSQL process is its child.
What this means
The supervisor process that is a running PostgreSQL server. It sets up the shared memory, opens the listening socket, forks a dedicated backend for each client that connects, starts the background helpers, and keeps watch over all of them. Every other Postgres process is one of its children.
Why it matters operationally
The postmaster is also the crash manager: if a backend dies unsafely, it resets shared memory and restarts every child to guarantee consistency, which is why a single backend crash briefly drops all connections. It never touches your data directly; it only supervises.