PostgreSQL Common Errors — Connection Refused, Authentication, and Query Failures

Overview

Fix common PostgreSQL errors including connection refused, authentication failures, permission denied, and query syntax errors on Linux servers.

Key Details

• PostgreSQL uses pg_hba.conf for client authentication and postgresql.conf for server settings
• Default installation only allows local connections — listen_addresses must be changed for remote access
• Common errors: FATAL: password authentication failed, could not connect to server, permission denied for table
• PostgreSQL roles (users) and database ownership affect what queries can be executed
• Connection pooling (PgBouncer, Pgpool-II) adds another layer of configuration and potential errors

Common Causes

• PostgreSQL not listening on the expected address/port (listen_addresses = 'localhost' by default)
• pg_hba.conf not allowing the client's authentication method or IP range
• User password incorrect or role does not exist in the database
• Insufficient privileges for the database role to access specific tables or schemas

Steps

1. 1Check if PostgreSQL is running: 'systemctl status postgresql' and 'ss -tlnp | grep 5432'
2. 2For remote connections: set 'listen_addresses = '*'' in postgresql.conf and add client entry in pg_hba.conf
3. 3Reset user password: 'sudo -u postgres psql -c "ALTER USER myuser PASSWORD 'newpassword';"'
4. 4Grant permissions: 'GRANT ALL PRIVILEGES ON DATABASE mydb TO myuser; GRANT ALL ON ALL TABLES IN SCHEMA public TO myuser;'
5. 5Check logs: 'tail -50 /var/log/postgresql/postgresql-[version]-main.log' for detailed error messages

Tags

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Frequently Asked Questions