Install istio1.9.0 on ubuntu failed

When I try to install istio1.9.0 on ubuntu, type this command: istioctl install --set profile=demo -y, get the below error:
Error: Get “HTTP://localhost:8080/api?timeout=32s”: dial tcp 127.0.0.1:8080: connect: connection refused

This means you are not connected to a kuberntees cluster. Look at Install and Set Up kubectl | Kubernetes

besides k8s, you may also look for minikube if you are playing with demo on local machine