Add note about permissions of installed files

README.md

@@ -160,6 +160,8 @@ acme.sh --installcert -d example.com \
 
 Only the domain is required, all the other parameters are optional.
 
+The ownership and permission info of existing files are preserved. You may want to precreate the files to have defined ownership and permission.
+
 Install/copy the issued cert/key to the production Apache or Nginx path.
 
 The cert will be `renewed every **60** days by default` (which is configurable). Once the cert is renewed, the Apache/Nginx service will be restarted automatically by the command: `service apache2 restart` or `service nginx restart`.