2.2Standard Bundled Tools

PostgreSQL ships with a standard set of bundled commands covering everything from starting the server to day-to-day interactive work and status checks. There are many to remember, but each has a clearly separated role, so mapping "which command for which task" turns this into reliable exam points.

2.2.1pg_ctl and user/database management commands

• pg_ctl is the central command for controlling the PostgreSQL server process. Its subcommands are start (start), stop (stop; -m selects the shutdown mode), reload (reload the configuration file only, keeping connections alive), restart (stop then start again), and status (check running status).
• createuser/dropuser are command-line tools for creating and dropping database roles (users). Internally they are wrappers that execute the SQL CREATE ROLE/DROP ROLE, with options such as -s (grant superuser privileges).
• createdb/dropdb are command-line tools for creating and dropping databases. Internally they wrap the SQL CREATE DATABASE/DROP DATABASE. By default they create the database by copying template1.

2.2.2psql and diagnostic commands

• psql is PostgreSQL's standard interactive terminal. Besides executing SQL statements, it supports meta-commands starting with \: \l (list databases), \c (switch database), \dt (list tables), \d (show the structure of a table etc.; \d tablename for detail), \du (list roles), \timing (toggle showing each query's execution time), \? (help for meta-commands), and \h (help for SQL commands).
• pg_config reports the installed PostgreSQL's build-time settings, version, and various directory paths (include directory, etc.). pg_controldata is a read-only tool that displays the control-file information for a data directory (cluster state, the latest checkpoint location, WAL timeline ID, and so on).
• pg_isready is a tool that quickly checks whether the server is ready to accept connections (used by monitoring scripts for liveness checks; judged via its exit code). pg_resetwal is a last-resort tool that resets a corrupted WAL (write-ahead log), forcibly returning an unstartable cluster to a startable state (it carries a risk of data inconsistency, so it is used only when no other option remains).

Picture a day of operations and the roles of these commands become clear. In the morning, a request comes in to change max_connections in postgresql.conf. Because this is a parameter that requires a restart, you safely stop and start again with pg_ctl restart -D $PGDATA. For a parameter that does not require a restart, such as changing only the log destination, you apply it without dropping connections using pg_ctl reload (or the SQL equivalent SELECT pg_reload_conf()), minimizing business impact. Next, a request arrives to provision a role and database for a new app: you create them in order with createuser app_user then createdb -O app_user app_db, and confirm the connection works with psql -U app_user -d app_db. Inside psql, the standard check is \l to confirm the new database appears in the list, and \du to visually confirm the app_user role exists with the intended privileges. In a monitoring context, a load balancer or orchestration tool periodically runs pg_isready -h dbhost, and if it detects anything other than exit code 0 (ready), it removes the node from rotation—wired into automation this way. Finally, in the serious scenario where a power outage or similar corrupts the cluster so badly it cannot even start, once every other recovery avenue is exhausted, pg_resetwal becomes the last-resort option—but you must understand its nature: it is a forced measure that prioritizes getting the server running again even at the cost of transactional consistency.

2.2.3Section summary

• pg_ctl = start/stop/reload/restart/status. reload keeps connections and only reloads config; restart drops connections and restarts
• createuser/dropuser, createdb/dropdb wrap CREATE/DROP ROLE and DATABASE. Distinguish psql meta-commands (\l, \dt, \du, \d, \c, \?, \h, \timing)
• pg_config = build info, pg_controldata = control-file info, pg_isready = liveness check, pg_resetwal = forced WAL reset (last resort)