`pg_ctlcluster` - start/stop/restart/reload/promote a PostgreSQL cluster (postgresql-common)

pg_ctlcluster [OPTIONS] <version> <cluster> <action> [-- <pg_ctl options>]

Options you will use

-m, --mode=smart|fast|immediate: shutdown mode for stop/restart: smart waits for clients, fast (default) disconnects them, immediate exits without a checkpoint (crash recovery on next start).
--skip-systemctl-redirect: do not hand over to systemctl (the unit itself uses this).
-f, --force: with stop: try fast, then immediate.
-o, --options=OPTIONS: pass options to postgres.

$ sudo pg_ctlcluster 18 main reload

SIGHUP: re-read the config

$ sudo pg_ctlcluster 18 replica promote

end recovery: the replica becomes a primary

$ sudo -u postgres pg_ctlcluster 18 main stop -m immediate

stop at once (crash recovery on start)

Try pg_ctlcluster in a real terminal Free, in your browser - a real Ubuntu terminal to try it in, with missions that check your work.