nginx-error_page.conf

# Add into server block
# Put maintenance page in /home/ubuntu/maintenance/maintenance.html

# Return a 503 error if the maintenance page exists.
if (-f /home/ubuntu/maintenance/maintenance.html) {
        return 503;
}

location @503 {
        if (-f $request_filename) {
                break;
        }

        root /home/ubuntu/maintenance/;
        rewrite ^(.*)$ /maintenance.html break;
}

error_page 503 @503;