January 21, 2023 By Matthew Rathbone *

If you are a Postgres user, you may have encountered the “peer authentication failed for user” error when trying to access a database. This error indicates that the user is not authorized to access the database.

You might get this error when trying to connect using the postgres user after just setting up your database for the first time. This is usually due to an incorrectly configured pg_hba.conf file. Read below to find out more.

Common causes

There are several common reasons why this error can occur.

Invalid credentials

This is the ‘real’ reason for the error - it indicates the user is not authorized to access the database. There’s not really a way to resolve this, other than double checking the credentials you are using.

Incorrect pg_hba.conf

One common cause is incorrect configuration in the pg_hba.conf file. This file controls the authentication method that Postgres uses to allow users to connect to the database. If the configuration is not set up correctly, users may not be able to authenticate and access the database.

OS user different from psql user

Another reason for this error is a mismatch between the operating system (OS) user name and the database user name. When connecting to Postgres, by default the OS user name is used to identify the user who is connecting to the database. If the OS user name does not match the database user name, the user will not be able to authenticate and access the database.

How to investigate the cause of the error

To troubleshoot this error, first check the pg_hba.conf file to make sure it is configured correctly.

Look for the line that specifies the authentication method for the user that is trying to connect to the database. Make sure it is set to “peer” for local connections or “md5” for remote connections.

If the configuration is correct, you can also try to connect to the database using the psql command-line interface. This will allow you to see the exact error message that is being returned by the database. The error message may provide more information about the specific cause of the authentication failure.

If you are unable to connect to the database using psql, you can try to connect as a different user. This will help you determine whether the issue is with the user account itself or with the authentication method.

Resolving the error

To resolve this error, you can try modifying the pg_hba.conf file to use a different authentication method. You can also try creating a new user account with a different name and granting it the necessary permissions to access the database.

Summary

In conclusion, the “peer authentication failed for user” error in Postgres can be caused by incorrect configuration in the pg_hba.conf file or a mismatch between the OS user name and the database user name. To troubleshoot and resolve this error, you can check the pg_hba.conf file, try to connect to the database using psql, and modify the authentication method or create a new user account.