Nginx 403 Forbidden: Troubleshooting File Access Permissions

When encountering the frustrating "403 forbidden" error in Nginx, determining the root cause can be a challenge. This error typically indicates that access to a file or directory is denied. In this specific scenario, the user has configured Nginx with PHP-FPM on CentOS 5, but is unable to serve any files from the specified source directory.

Upon examination, the issue stems from insufficient file permissions. Nginx runs as the 'www-data' user, and the 'public_html' directory, which contains the files being served, should have accessible permissions for this user. While the directory permissions are set to 2777, allowing 'www-data' to read, write, and execute, there's a crucial detail often missed.

Overlooked Permission: Execute Access

In addition to the permissions on the 'public_html' directory, Nginx requires execute permissions for all parent directories in the path leading to the file. In this case, the directory 'demo' would also need executable permissions for 'www-data' to access any subdirectory below it.

Recommended Solution

To resolve the issue, the user should check the permissions of all parent directories to ensure that 'www-data' has execute access. Typically, a simple command like 'chmod o x /path/to/parentDirectory' would suffice to add executable permissions for the 'other' users, including 'www-data'.

Troubleshooting Tip

To quickly display all the permissions on a path, the user can employ the command 'namei -om /path/to/check'. This comprehensive output will provide a detailed breakdown of the permissions for each directory and file along the specified path.