Check if netstat or iproute2 is available

hack/lib/etcd.sh

@@ -22,13 +22,22 @@ ETCD_PORT=${ETCD_PORT:-2379}
 
 kube::etcd::validate() {
   # validate if in path
-  which etcd >/dev/null || {
+  command -v etcd >/dev/null || {
     kube::log::usage "etcd must be in your PATH"
     exit 1
   }
 
   # validate etcd port is free
-  if netstat -nat | grep "[\.:]${ETCD_PORT:?} .*LISTEN" >/dev/null 2>&1; then
+  local port_check_command
+  if command -v ss &> /dev/null && ss -Version | grep 'iproute2' &> /dev/null; then
+    port_check_command="ss"
+  elif command -v netstat &>/dev/null; then
+    port_check_command="netstat"
+  else
+    kube::log::usage "unable to identify if etcd is bound to port ${ETCD_PORT}. unable to find ss or netstat utilities."
+    exit 1
+  fi
+  if ${port_check_command} -nat | grep "LISTEN" | grep "[\.:]${ETCD_PORT:?}" >/dev/null 2>&1; then
     kube::log::usage "unable to start etcd as port ${ETCD_PORT} is in use. please stop the process listening on this port and retry."
     kube::log::usage "`netstat -nat | grep "[\.:]${ETCD_PORT:?} .*LISTEN"`"
     exit 1