I am using certbot to apply Let's Encrypt certificate,my server is centos 7.2 and nginx 1.11.9.what does this mean below?
[root@test ~]# certbot certonly --webroot -w /var/www/www.example.com -d example.com -d www.example.comFailed authorization procedure. example.com (http-01): urn:acme:error:unauthorized :: The client lacks sufficient authorization :: Invalid response from http://example.com/.well-known/acme-ch<head><title>404 Not Found</title></head><body bgcolor="white"><center><h1>404 Not Found</h1></center><hr><center>", www.example.com (http-01): urn:acme:error:unauthorized :: The client lacks sufficient authorization :: Invalid response from http://www.example.com/.well-known/acme-challenge/k<head><title>404 Not Found</title></head><body bgcolor="white"><center><h1>404 Not Found</h1></center><hr><center>"IMPORTANT NOTES: - If you lose your account credentials, you can recover through e-mails sent to example@example.com. - The following errors were reported by the server: Domain: example.com Type: unauthorized Detail: Invalid response from http://example.com/.well-known/acme-challenge/wGNv57IGJjHQ9wyzzALktpNaPzfnTtN3m7u3QuO4p40:"<html><head><title>404 Not Found</title></head><body bgcolor="white"><center><h1>404 Not Found</h1></center><hr><center>" Domain: www.example.com Type: unauthorized Detail: Invalid response from http://www.example.com/.well-known/acme-challenge/kFJ0CSuKOdgcT2xmciB4GGNCcnUPoIbpQmA9jOII_Bk:"<html><head><title>404 Not Found</title></head><body bgcolor="white"><center><h1>404 Not Found</h1></center><hr><center>" To fix these errors, please make sure that your domain name was entered correctly and the DNS A record(s) for that domain contain(s) the right IP address. - Your account credentials have been saved in your Certbot configuration directory at /etc/letsencrypt. You should make a secure backup of this folder now. This configuration directory will also contain certificates and private keys obtained by Certbot so making regular backups of this folder is ideal.I can access example.com and www.example.com,and there is a note in docs: https://certbot.eff.org/#centosrhel7-nginx
Note: To use the webroot plugin, your server must be configured to serve files from hidden directories. If /.well-known is treated specially by your webserver configuration, you might need to modify the configuration to ensure that files inside /.well-known/acme-challenge are served by the webserver.
Is that the reason?How to modify the configuration?