describe certbot usage

cert/README.md

@@ -0,0 +1,30 @@
+# Local host
+
+```
+sudo cert/clientRenew
+```
+
+When the certbot script asks you to provide verification, go to remote host
+
+# Remote host
+
+```
+sudo cert/vpsRenew ACME_FILE ACME_VALUE
+```
+
+The script waits for Return key, now go to local host and press Return
+to let certbot generate certificate and key
+
+# Local host
+
+Press Return
+
+# Remote host
+
+Press Return
+
+# Local to remote
+
+Copy certificate and key to the remove host
+
+Restart Nginx