Why PostgreSQL Returns ‘FATAL: password authentication failed’ and How to Fix It

PostgreSQL Database Connection Error: “FATAL: password authentication failed for user “postgres””

1. Environment Overview

1.1 Practice Environment

The environment uses yum to install PostgreSQL on a CentOS 7.6 host (IP 192.168.3.166) with PostgreSQL 13.10.

1.2 PostgreSQL Overview

PostgreSQL (Postgres) is an open‑source relational database management system that implements all mainstream SQL features, supports transactions, concurrency control, complex queries, foreign keys, triggers, stored procedures, and offers high extensibility, stability, and security, making it a popular choice for enterprise applications.

1.3 PostgreSQL Features

Open‑source and free.

Highly extensible for large data and high concurrency.

Supports many data types such as JSON, arrays, ranges, XML, UUID.

Provides various backup and recovery methods.

Security mechanisms including SSL/TLS, access control, authentication, and authorization.

Extensible with extensions like spatial data and full‑text search.

2. Error Scenario

Remote connection to PostgreSQL fails with a password authentication error.

[root@jeven ~]# psql -h192.168.3.166 -Upostgres -W
Password:
psql: error: FATAL:  password authentication failed for user "postgres"

3. Cause Analysis

Incorrect password entered.

Misconfiguration in /var/lib/pgsql/13/data/postgresql.conf.

Misconfiguration in /var/lib/pgsql/13/data/pg_hba.conf.

Error when setting the database user password.

4. Check Configuration

Verify listen_addresses = '*' in postgresql.conf.

listen_addresses = '*'	# what IP address(es) to listen on;

Verify authentication lines in pg_hba.conf.

host    all            all      127.0.0.1/32      ident
host    all            all      0.0.0.0/0         md5

After confirming the settings, restart the PostgreSQL service and test again.

5. Solutions for Common Scenarios

5.1 Forgot Login Password

Log in locally as the postgres user and reset the password.

su - postgres

psql -c "ALTER USER postgres WITH PASSWORD 'postgres';"

5.2 Incorrect or Missing Password Setting

The password was typed incorrectly; reset it.

sudo -u postgres
psql -c "ALTER USER postgres WITH PASSWORD 'postgres';"

5.3 Configuration File Errors

Check and correct postgresql.conf and pg_hba.conf as shown above.

Verify listen_addresses = '*' in postgresql.conf.

listen_addresses = '*'	# what IP address(es) to listen on;

Verify authentication lines in pg_hba.conf.

host    all            all      127.0.0.1/32      ident
host    all            all      0.0.0.0/0         md5

Restart the service after corrections.

5.4 Set Trust Authentication (Password‑less Login)

Temporarily change pg_hba.conf to trust authentication, reset the password, then revert the file.

vim /var/lib/pgsql/13/data/pg_hba.conf

host    all            all      127.0.0.1/32     trust
host    all            all      0.0.0.0/0        trust

5.5 Environment Issues

Deploy PostgreSQL on a clean or new environment if the current setup is corrupted.

6. Summary of PostgreSQL Connection Errors

Incorrect connection parameters (address, port, username, password).

Database service not started.

Insufficient user privileges.

Firewall or network blockage.

Misconfigured configuration files.

Client‑server version incompatibility.