Resolving Password Authentication Failure for 'postgres' User When Connecting to PostgreSQL 13 via pgAdmin 4

Problem Background and Symptom Analysis

When using pgAdmin 4 to connect to a PostgreSQL 13 database, many users encounter a common yet frustrating issue: the system prompts for the password of the 'postgres' user, but the user is unaware of what this password is. Attempting to use default passwords (such as empty or common combinations) results in the error “FATAL: password authentication failed for user "postgres"”, while omitting the password yields “fe_sendauth: no password supplied”. This problem typically occurs after a fresh installation of PostgreSQL 13, especially on macOS or Windows systems where pgAdmin 4 is integrated as a graphical management tool with the PostgreSQL server.

Root Cause of the Core Issue

The root cause lies in PostgreSQL 13's default use of the scram-sha-256 authentication method, an enhanced security mechanism that requires users to set and remember passwords. However, during installation, users may not have explicitly set a password for the 'postgres' user, or the password might not have been recorded correctly. Additionally, configuration entries in the pg_hba.conf file (e.g., local all all scram-sha-256) enforce password authentication, even for local connections. This leads to the same authentication barrier when users try to access via command-line tools like psql.

Detailed Solution

Based on the best answer (score 10.0), here is a systematic approach to resolve this issue, applicable to most operating system environments (e.g., Windows, macOS, and Linux).

Step 1: Temporarily Modify Authentication Method

First, temporarily modify the pg_hba.conf file to change the authentication method from scram-sha-256 to trust, allowing password-less access. This file is usually located in the data folder of the PostgreSQL installation directory. For example, on Windows, the path might be C:\Program Files\PostgreSQL\13\data\pg_hba.conf; on macOS or Linux, it could be /usr/local/var/postgresql@13/pg_hba.conf or a similar location. Open the file with a text editor (e.g., Notepad++ or vim) and replace the METHOD field in all lines from scram-sha-256 to trust. A modified example snippet is as follows:

# TYPE  DATABASE        USER            ADDRESS                 METHOD
local   all             all                                     trust
host    all             all             127.0.0.1/32            trust
host    all             all             ::1/128                 trust

After saving the file, restart the PostgreSQL service for the changes to take effect. On Windows, this can be done via the Services Manager by restarting the “PostgreSQL 13” service; on macOS or Linux, use commands like brew services restart postgresql@13 or sudo systemctl restart postgresql-13.

Step 2: Reset Password via Command Line

With the authentication method set to trust, you can access the database without a password. Open a command-line terminal, ensuring that PostgreSQL's bin directory is added to the system path. Then execute the following command:

psql -U postgres

This will connect to the PostgreSQL server as the 'postgres' user without prompting for a password. Once in the psql interactive interface, run the following command to reset the password:

\password postgres

The system will prompt you to enter a new password and confirm it. Choose a strong password and remember it, such as a combination of letters, numbers, and special characters. After successfully setting the password, type \q to exit psql.

Step 3: Restore Security Configuration

After resetting the password, you must revert the pg_hba.conf file to its original state to re-enable scram-sha-256 authentication and ensure database security. Reopen the pg_hba.conf file and change all instances of trust back to scram-sha-256. Then restart the PostgreSQL service again.

Step 4: Test the Connection

Now, test the connection in pgAdmin 4. Open pgAdmin 4, enter the master password if prompted, and attempt to connect to the “PostgreSQL 13” server. When asked for the 'postgres' user password, enter the newly set password. If everything is correct, the connection should be established successfully, allowing you to start managing the database.

Supplementary References and Considerations

Referring to other answers (e.g., the one with a score of 5.7), on Linux systems like Ubuntu 20.04, a similar approach can be used with slightly different commands. For example, switch to the 'postgres' user via sudo su postgres, then run psql and \password postgres. This highlights the universal principle across operating systems: temporarily relax authentication, reset the password, and restore security.

Important considerations: Throughout the process, ensure that trust authentication is used only temporarily when necessary and restored promptly to avoid potential security risks. Additionally, if the issue persists, checking PostgreSQL log files (usually in the log folder within the data directory) may help diagnose other configuration problems.

Conclusion

By following the steps outlined above, users can effectively resolve the password authentication failure for the 'postgres' user when connecting to PostgreSQL 13 via pgAdmin 4. This method not only applies to the current scenario but also illustrates a general strategy for handling database authentication issues: understand configuration mechanisms, temporarily adjust to regain access, securely reset credentials, and ultimately strengthen system security. For more complex environments, refer to the official PostgreSQL documentation for further guidance.