During the installation of PostgreSQL on Windows, many users encounter the following error message:
"Problem running post-install step. Installation may not complete correctly. The database cluster initialization failed."
In this article, we’ll explain the causes of this issue and provide a step-by-step guide to resolve it.

What Causes This Error?

This error occurs when PostgreSQL fails to complete the "post-install" configuration steps. The primary reasons for this include:

Incorrect locale selection: Choosing certain locales (e.g., Turkish) can cause issues during PostgreSQL initialization.
Insufficient permissions: Running the installer without proper administrative privileges.
Leftover files from previous installations: Remnants from old PostgreSQL installations can interfere with the new setup.

Steps to Resolve the Issue

Follow these steps to fix the problem:

1. Remove Any Existing PostgreSQL Installation

Go to "Add or Remove Programs" on your computer and uninstall PostgreSQL.
If the uninstallation fails or gives errors, proceed to the next step without worrying.
After removing the program, navigate to the C:\Program Files\PostgreSQL directory and delete all files and folders in this location.

2. Run the Installer as Administrator

Right-click on the PostgreSQL installer and select "Run as Administrator".

3. Adjust the Locale Setting

During the installation process, you will see a "Default Locale" option.
If you select the default locale for Turkey (Turkish_Turkey), the installation is likely to fail.
Instead, choose English, United States (America) as the locale.

4. Complete the Installation

After selecting the correct locale, proceed with the installation.
The process should now complete without any errors.

5. Verify the Installation

Once the installation is complete, ensure PostgreSQL is working correctly:
1. Use pgAdmin or the terminal to connect to PostgreSQL.
2. Test by creating a database and running basic queries.

Why Does Locale Selection Matter?

PostgreSQL relies on system locale settings during the initialization of the "database cluster." Certain locale settings, such as Turkish_Turkey, can lead to errors during this process. Selecting a more universal locale like English, United States prevents such issues.

Conclusion

If you encounter the "Database Cluster Initialization Failed" error during PostgreSQL installation, the steps above should help you resolve it quickly. Correct locale selection, in particular, is critical to avoiding this issue.