I tried to install Kubernetes with kubeadm on 3 virtual machines with Debian OS on my laptop, one as master node and the other two as worker nodes. I did exactly as the tutorials on kubernetes.io suggests. I initialized cluster with command kubeadm init --pod-network-cidr=10.244.0.0/16 and joined the workers with corresponding kube join command. I installed Flannel as the network overlay with command kubectl apply -f https://raw.githubusercontent.com/coreos/flannel/master/Documentation/kube-flannel.yml.
The repsonse of command kubectl get nodes looks fine:
NAME STATUS ROLES AGE VERSION INTERNAL-IP EXTERNAL-IP OS-IMAGE
k8smaster Ready master 20h v1.18.3 192.168.1.100 <none> Debian GNU/Linux 10 (buster) 4.19.0-9-amd64 docker://19.3.9
k8snode1 Ready <none> 20h v1.18.3 192.168.1.101 <none> Debian GNU/Linux 10 (buster) 4.19.0-9-amd64 docker://19.3.9
k8snode2 Ready <none> 20h v1.18.3 192.168.1.102 <none> Debian GNU/Linux 10 (buster) 4.19.0-9-amd64 docker://19.3.9
The response of command kubectl get pods --all-namespaces doesn't show any error:
NAMESPACE NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
kube-system coredns-66bff467f8-7hlnp 1/1 Running 9 20h 10.244.0.22 k8smaster <none> <none>
kube-system coredns-66bff467f8-wmvx4 1/1 Running 11 20h 10.244.0.23 k8smaster <none> <none>
kube-system etcd-k8smaster 1/1 Running 11 20h 192.168.1.100 k8smaster <none> <none>
kube-system kube-apiserver-k8smaster 1/1 Running 9 20h 192.168.1.100 k8smaster <none> <none>
kube-system kube-controller-manager-k8smaster 1/1 Running 11 20h 192.168.1.100 k8smaster <none> <none>
kube-system kube-flannel-ds-amd64-9c5rr 1/1 Running 17 20h 192.168.1.102 k8snode2 <none> <none>
kube-system kube-flannel-ds-amd64-klw2p 1/1 Running 21 20h 192.168.1.101 k8snode1 <none> <none>
kube-system kube-flannel-ds-amd64-x7vm7 1/1 Running 11 20h 192.168.1.100 k8smaster <none> <none>
kube-system kube-proxy-jdfzg 1/1 Running 11 19h 192.168.1.101 k8snode1 <none> <none>
kube-system kube-proxy-lcdvb 1/1 Running 6 19h 192.168.1.102 k8snode2 <none> <none>
kube-system kube-proxy-w6jmf 1/1 Running 11 20h 192.168.1.100 k8smaster <none> <none>
kube-system kube-scheduler-k8smaster 1/1 Running 10 20h 192.168.1.100 k8smaster <none> <none>
Then i tried to create a POD with command kubectl apply -f podexample.yml with following content:
apiVersion: v1
kind: Pod
metadata:
name: example
spec:
containers:
- name: nginx
image: nginx
Command kubectl get pods -o wide shows that the POD is created on worker node1 and is in Running state.
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
example 1/1 Running 0 135m 10.244.1.14 k8snode1 <none> <none>
The thing is, when i try to connect to the pod with curl -I 10.244.1.14 command i get the following response in master node:
curl: (7) Failed to connect to 10.244.0.14 port 80: No route to host
但是工作节点1上的同一命令成功响应：
HTTP/1.1 200 OK
Server: nginx/1.17.10
Date: Sat, 23 May 2020 19:45:05 GMT
Content-Type: text/html
Content-Length: 612
Last-Modified: Tue, 14 Apr 2020 14:19:26 GMT
Connection: keep-alive
ETag: "5e95c66e-264"
Accept-Ranges: bytes
I thought maybe that's because somehow kube-proxy is not running on master node but command ps aux | grep kube-proxy shows that it's running.
root 16747 0.0 1.6 140412 33024 ? Ssl 13:18 0:04 /usr/local/bin/kube-proxy --config=/var/lib/kube-proxy/config.conf --hostname-override=k8smaster
Then i checked for kernel routing table with command ip route and it shows that packets destined for 10.244.1.0/244 get routed to flannel.
default via 192.168.1.1 dev enp0s3 onlink
10.244.0.0/24 dev cni0 proto kernel scope link src 10.244.0.1
10.244.1.0/24 via 10.244.1.0 dev flannel.1 onlink
10.244.2.0/24 via 10.244.2.0 dev flannel.1 onlink
169.254.0.0/16 dev enp0s3 scope link metric 1000
172.17.0.0/16 dev docker0 proto kernel scope link src 172.17.0.1 linkdown
192.168.1.0/24 dev enp0s3 proto kernel scope link src 192.168.1.100
一切对我来说看起来很好，我不知道该怎么办才能检查出什么问题。我想念什么吗？
更新：
If i start an NGINX container on worker node1 and map it's 80 port to port 80 of the worker node1 host, then i can connect to it via command curl -I 192.168.1.101 from master node. Also, i didn't add any iptable rule and there is no firewall daemon like UFW installed on the machines. So, i think it's not a firewall issue.
