PostgreSQL

Unless otherwise noted, non-SQL commands are running under Ubuntu.

# On Ubuntu, run psql as default postgres user.
sudo -u postgres psql

# List all databases.
sudo -u postgres psql -l

-- List all databases.
\l

-- Quit psql.
\q

Configuration

# Show the full path to the PostgreSQL configuration file.
sudo -u postgres psql -c 'SHOW config_file'
# Example: /etc/postgresql/12/main/postgresql.conf

# Show the full path to the HBA configuration file.
sudo -u postgres psql -c 'SHOW hba_file'
# Example: /etc/postgresql/12/main/pg_hba.conf

-- Locate the HBA configuration file.
SHOW hba_file;
-- Example: /etc/postgresql/12/main/pg_hba.conf

-- Or just query the file for rules.
select * from pg_hba_file_rules();

User management

-- List all users.
\du

-- Create a new user.
CREATE USER <name>;

Database management

# Create a new database.
sudo -u postgres createdb <name>
# Verify it was created.
sudo -u postgres psql -l

# Create a new database, echoing out the commands run.
sudo -u postgres createdb <name> -e

# Drop a database.
sudo -u postgres dropdb <name>