If you don't have HTTP server configured, you can run the following
command on the target server (as root):
mkdir -p /tmp/letsencrypt/public_html/.well-known/acme-challenge
cd /tmp/letsencrypt/public_html
printf "%s" QmE0GFyF7PwX4J8a6F9PItO0q7erTw3rDrtBAgP9Gpw.lpqNGa7M3bSSl6E-RWIMaZqkbsbWrkV7mECugTTW9aU > .well-known/acme-challenge/QmE0GFyF7PwX4J8a6F9PItO0q7erTw3rDrtBAgP9Gpw
run only once per server:
$(command -v python2 || command -v python2.7 || command -v python2.6) -c
"import BaseHTTPServer, SimpleHTTPServer;
s = BaseHTTPServer.HTTPServer(('', 80), SimpleHTTPServer.SimpleHTTPRequestHandler);
s.serve_forever()"
Press ENTER to continue
if I try I get a "file not found" possibly as the file has since been removed, or it could be because you have some redirects in place which don't provide access to that folder / file.
When i execute the command, i create the folder and file with the key before press continue, and my browser reach the file correctly, but LE client get error unauthorized : 15 parts , What is this error ?