[viirb2] allow to inject private key

viirb-2-configure-fully-after-upgrade.sh

@@ -3,9 +3,10 @@
 # See https://ungleich.ch/u/products/viirb-ipv6-box/
 
 if [ $# -ne 2 ]; then
-    echo "$0 viirb-ip-address viirb-id"
+    echo "$0 viirb-ip-address viirb-id [wgprivkey]"
     echo "    viirb-ip-address: where to find the viirb"
     echo "    viirb-id: number in decimal format"
+    echo "    wgprivkey: if specified, use this private key"
     exit 1
 fi
 
@@ -25,7 +26,11 @@ my_lan_ip=${my_prefix}:cafe::42
 my_wifi_ip=${my_prefix}:7ea::42
 
 # wireguard
-private_key=$(wg genkey)
+if [ $# -eq 1 ]; then
+    private_key=$1; shift
+else
+    private_key=$(wg genkey)
+fi
 public_key=$(echo $private_key | wg pubkey)
 
 vpn_endpoint_host=vpn-2a0ae5c1300.ungleich.ch