:memo: Explain how to move a certbot install

Guides/httpd.md

@@ -17,3 +17,9 @@ Enable a configuration by creating a likn in `/etc/apache2/sites-enabled`
 To renew certificates :
 
 `sudo certbot --apache renew`
+
+### To move certificates
+
+Step 1 : Copy `/etc/letsencrypt/{live, archive}` from old install to new install.
+
+Step 2 : Copy or configure renewal in `/etc/letsencrypt/renewal`.