Why can I not use port 80 when using K3s Kubernetes - kubernetes

Question

I have a simple NodeJS project running on a K3s cluster on a Raspberry Pi 4. The cluster has a service to expose it. The code is as follows...
spec:
type: LoadBalancer
ports:
- protocol: TCP
port: 3000
targetPort: 3000
I want to try and use port 80 instead of 3000 so I try...
spec:
type: LoadBalancer
ports:
- protocol: TCP
port: 80
targetPort: 3000
But it can't use the port.
Warning FailedScheduling 5m 0/1 nodes are available: 1 node(s) didn't have free ports for the requested pod ports.
Why am I having issues?
Update
Per the answer I tried...
pi#raspberrypi:~ $ sudo netstat -tulpn | grep :80
pi#raspberrypi:~ $ sudo ss -tulpn | grep :80
pi#raspberrypi:~ $
My guess is this is a K3s or Pi limitation.
Update 2
When I run kubectl get service --all-namespaces
NAMESPACE NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
default kubernetes ClusterIP 10.43.0.1 <none> 443/TCP 24d
kube-system kube-dns ClusterIP 10.43.0.10 <none> 53/UDP,53/TCP,9153/TCP 24d
kube-system metrics-server ClusterIP 10.43.48.200 <none> 443/TCP 24d
kube-system traefik-prometheus ClusterIP 10.43.89.96 <none> 9100/TCP 24d
kube-system traefik LoadBalancer 10.43.65.154 192.168.x.xxx 80:31065/TCP,443:32574/TCP 24d
test-namespace app-tier LoadBalancer 10.43.190.179 192.168.x.xxx 3000:31500/TCP 4d

Answer 1

k3s comes with a pre-installed traefik ingress controller which binds to 80, 443 and 8080 on the host, alhtough you should have seen that with ss or netstat
You should see this service if you run:
kubectl get service --all-namespaces
Although you should have seen it with netstat or ss if something is using the port if this is the case. But mb this service also failed to deploy but somehow blocks k3s from taking the port.
Another thing I can think of: Are you running the experimental rootless setup?