How to shutdown postgres through psql?

Question

The recommended way to shutdown postgres is to send a signal representing the different shutdown modes (fast, smart, immediate) or using init managers (initd, systemd, etc.) or their equivalent on non-Linux OS. In a containerized environment it's sometimes more convenient to gain access through psql than docker exec and thus more convenient to stop the server through psql. Is there a way to do that (given that the privileges have been granted)?

The solution can be hacky since this will mostly be used to stop a postgres to delete a PostgreSQL data directory in a development environment.

Answer 1

The documentation tells you to send a signal to the master postgres process, or to let pg_ctl do this.

In SQL, you can extract the PID of the master process from pg_read_file('postmaster.pid'), but pg_cancel_backend() does not accept this PID.

However, you should be able to execute these commands with COPY (depending on what rights the postgres OS user has):

COPY (SELECT 1) TO PROGRAM 'kill -INT `head -1 /usr/local/pgsql/data/postmaster.pid`';

COPY (SELECT 1) TO PROGRAM 'pg_ctl -D /usr/local/pgsql/data stop';