Problem
To make k8s multinodes dev env, I was trying to use NFS persistent volume in minikube with multi-nodes and cannot run pods properly. It seems there's something wrong with NFS setting. So I run minikube ssh and tried to mount the nfs volume manually first by mount command but it doesnt work, which bring me here.
When I run
sudo mount -t nfs 192.168.xx.xx(=macpc's IP):/PATH/TO/EXPORTED/DIR/ON/MACPC /PATH/TO/MOUNT/POINT/IN/MINIKUBE/NODE
in minikube master node, the output is
mount.nfs: requested NFS version or transport protocol is not supported
Some relavant info is
NFS client: minikube nodes
NFS server: my Mac PC
minikube driver: docker
Cluster comprises 3 nodes. (1 master and 2 worker nodes)
Currently there's no k8s resources (such as deployment, pv and pvc) in cluster.
minikube nodes' os is Ubuntu so I guess "nfs-utils" is not relavant and not installed. "nfs-common" is preinstalled in minikube.
Please see the following sections for more detail.
Goal
The goal is mount cmd in minikube nodes succeeds and nfs share on my Mac pc mounts properly.
What I've done so far is
On NFS server side,
created /etc/exports file on mac pc. The content is like
/PATH/TO/EXPORTED/DIR/ON/MACPC　-mapall=user:group 192.168.xx.xx(=the output of "minikube ip")
and run nfsd update and then showmount -e cmd outputs
Exports list on localhost:
/PATH/TO/EXPORTED/DIR/ON/MACPC 192.168.xx.xx(=the output of "minikube ip")
rpcinfo -p shows rpcbind(=portmapper in linux), status, nlockmgr, rquotad, nfs, mountd are all up in tcp and udp
ping 192.168.xx.xx(=the output of "minikube ip") says
Request timeout for icmp_seq 0
Request timeout for icmp_seq 1
Request timeout for icmp_seq 2
and continues
It seems I can't reach minikube from host.
On NFS client side,
started nfs-common and rpcbind services with systemctl cmd in all minikube nodes. By running sudo systemctl status rpcbind and sudo systemctl status nfs-common, I confirmed rpcbind and nfs-common are running.
minikube ssh output
Last login: Mon Mar 28 09:18:38 2022 from 192.168.xx.xx(=I guess my macpc's IP seen from minikube cluster)
so I run
sudo mount -t nfs 192.168.xx.xx(=macpc's IP):/PATH/TO/EXPORTED/DIR/ON/MACPC /PATH/TO/MOUNT/POINT/IN/MINIKUBE/NODE
in minikube master node.
The output is
mount.nfs: requested NFS version or transport protocol is not supported
rpcinfo -p shows only portmapper and status are running. I am not sure this is ok.
ping 192.168.xx.xx(=macpc's IP) works properly.
ping host.minikube.internal works properly.
nc -vz 192.168.xx.xx(=macpc's IP) 2049 outputs connection refused
nc -vz host.minikube.internal 2049 outputs succeeded!
Thanks in advance!
I decided to use another type of volume instead.
Related
cluster info:
Minikube installation steps on centos VM:
curl -LO https://storage.googleapis.com/minikube/releases/v1.21.0/minikube-linux-amd64
sudo install minikube-linux-amd64 /usr/local/bin/minikube
minikube start --addons=ingress --vm=true --memory=8192 --driver=none
PODs of this minikube cluster are not able to connect to internet.
However My host VM has internet connection with no firewall or iptables setup.
Can anybody help me debug this connection refused error
UPDATE:
I have noticed just now , I am able to connect non-https URLs, but not https URLs
How you have started the Minikube on the VM ? Which command did you used ?
If you are using the minikube --driver=docker it might won't work.
for starting the minikube on VM you have to change the driver
minikube --driver=none
in docker driver, it will create the container and install the kubernetes inside it and spawn the POD into further.
Check more at : https://minikube.sigs.k8s.io/docs/drivers/none/
if you on docker you can try :
pkill docker
iptables -t nat -F
ifconfig docker0 down
brctl delbr docker0
docker -d
"It will force docker to recreate the bridge and reinit all the network rules"
reference : https://github.com/moby/moby/issues/866#issuecomment-19218300
Try with
docker run --net=host -it ubuntu
Or else add dns in the config file in /etc/default/docker
DOCKER_OPTS="--dns 208.67.222.222 --dns 208.67.220.220"
Please check your container port and target port. This is my pod setup:
spec:
containers:
name: hello
image: "nginx"
ports:
containerPort: 5000
This is my service setup:
ports:
protocol: TCP
port: 60000
targetPort: 5000
If your target port and container port don't match, you will get a curl: (7) connection refused error(Source).
Checkout similar Stackoverflowlink for more information.
I install a 3 node Kubernetes Cluster with RKE tool. The installation was successful with no errors but I'm unable to ping from one pod to another pod.
If I ping a pod running on worker2 node(NODE-IP-10.222.22.47) I get a response, but no responses from pods running on worker1(NODE-IP-10.222.22.46).
My Pods are as follows -
Also I noticed for some pods it has given node-ip addresses. The node IP addresses are
Master1=10.222.22.45
Worker1=10.222.22.46
Worker2=10.222.22.47
cluster_cidr: 10.42.0.0/16
service_cluster_ip_range: 10.43.0.0/16
cluster_dns_server: 10.43.0.10
Overlay network - canal
OS- CentOS Linux release 7.8.2003
Kubernetes - v1.20.8 installed with rke tool
Docker - 20.10.7
Sysctl entries in all nodes
firewall was disabled in all nodes before install.
Check - sysctl net.bridge.bridge-nf-call-ip6tables
net.bridge.bridge-nf-call-ip6tables = 1
Check - sysctl net.bridge.bridge-nf-call-iptables
net.bridge.bridge-nf-call-iptables = 1
From description and screenshots provided, some addons and
controllers of master01 do not seem ready, which might need to be
reconfigured.
You can also use routes to connect to pods on worker1. Check this for
detailed instructions.
The reason was the UDP ports were blocked
Below is the output:
C:\Windows\system32>kubectl cluster-info
Kubernetes master is running at https://127.0.0.1:32772
KubeDNS is running at https://127.0.0.1:32772/api/v1/namespaces/kube-system/services/kube-dns:dns/proxy
To further debug and diagnose cluster problems, use 'kubectl cluster-info dump'.
C:\Windows\system32>
I am using Minikube to run a single Node cluster in my local box to lean Kubernetes. I Google'ed Minikube docs and what I understood was that Minikube will launch a VM (in my case I used Oracle VirtualBox) in my local and runs a single Node Kubernetes cluster in the VM.
In the above output, "Kubernetes master is running at https://127.0.0.1:32772" means Kubernetes master is running on my local box or inside the VM launched by Minikube?
UPDATE 1:
I tried to see which service is running on this port and below is the output:
C:\Users>netstat -a -o -n | find "32772"
TCP 127.0.0.1:32772 0.0.0.0:0 LISTENING 8892
C:\Users>
And 8892 is running com.backend.docker.exe. I am more confused now that is Docker running my cluster, if not then why it is showing that com.backend.docker.exe is running on port "32772".
Both assumptions are correct.
It's running in a VM, a VM which is running in your PC and exposing the Kubernetes API so that you can access it with kubectl without needing to get into the VM.
Below are the commands and their outputs:
root#k8s-master:~# sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
cp: cannot stat '/etc/kubernetes/admin.conf': No such file or directory
root#k8s-master:~# kubectl get services -n kube-system
The connection to the server localhost:8080 was refused - did you specify the right host or port?
It looks like you are not running EKS. Otherwise you cannot access the masters. With EKS, the masters are managed by AWS and you can't ssh to them
your kubectl commands makes a call to the kubernetes api server. So you have to check if it is running on localhost on port 8080.
I was able to cluster 2 nodes together in Kubernetes. The master node seems to be running fine but running any command on the worker node results in the error: "The connection to the server localhost:8080 was refused - did you specify the right host or port?"
From master (node1),
$ kubectl get nodes
NAME STATUS AGE VERSION
node1 Ready 23h v1.7.3
node2 Ready 23h v1.7.3
From worker (node 2),
$ kubectl get nodes
The connection to the server localhost:8080 was refused - did you specify the right host or port?
$ telnet localhost 8080
Trying ::1...
telnet: connect to address ::1: Connection refused
Trying 127.0.0.1...
telnet: connect to address 127.0.0.1: Connection refused
$ ping localhost
PING localhost (127.0.0.1) 56(84) bytes of data.
64 bytes from localhost (127.0.0.1): icmp_seq=1 ttl=64 time=0.032 ms
I am not sure how to fix this issue. Any help is appreciated.
On executing,"journalctl -xeu kubelet" I see:
"CNI failed to retrieve network namespace path: Cannot find network namespace for the terminated container", but this seems to be related to installing a pod network ... which I am not able to because of the above error.
Thanks!
kubectl interfaces with kube-apiserver for cluster management. The command works on the master node because that's where kube-apiserver runs. On the worker nodes, only kubelet and kube-proxy is running.
In fact, kubectl is supposed to be run on a client (eg. laptop, desktop) and not on the kubernetes nodes.
from master you need ~/.kube/config pass this file as argument for kubectl command. Copy the config file to other server or laptop then pass the argument as for kubectl command
eg:
kubectl --kubeconfig=~/.kube/config
This worked for me after executing following commands:
$ sudo mkdir -p $HOME/.kube
$ sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
$ sudo chown $(id -u):$(id -g) $HOME/.kube/config
As a hint, the message being prompted indicates its related to network.
So one potential answer could also be, which worked for my resolution, is to have a look at the key cluster value for context within contexts.
My error was that I had placed an incorrect cluster name there.
Having the appropriate cluster name is crucial to finding it for respective context and the error will disappear.
To solve the issue The connection to the server localhost:8080 was refused - did you specify the right host or port?, you may be missing a step.
My Fix:
On MacOS if you install K8s with brew, you still need to brew install minikube, afterwards you should run minikube start. This will start your cluster.
Run the command kubectl cluster-info and you should get a happy path response similar to:
Kubernetes control plane is running at https://127.0.0.1:63000
KubeDNS is running at https://127.0.0.1:63308/api/v1/namespaces/kube-system/services/kube-dns:dns/proxy
Kubernetes install steps: https://kubernetes.io/docs/tasks/tools/install-kubectl-macos/
Minikube docs: https://minikube.sigs.k8s.io/docs/start/
Ensure what context is selected if you're running Kubernetes in the Docker Desktop.
Once you've selected it right, you'll be able to run the kubectl commands without any exception:
% kubectl cluster-info
Kubernetes control plane is running at https://kubernetes.docker.internal:6443
CoreDNS is running at https://kubernetes.docker.internal:6443/api/v1/namespaces/kube-system/services/kube-dns:dns/proxy
To further debug and diagnose cluster problems, use 'kubectl cluster-info dump'.
% kubectl get nodes
NAME STATUS ROLES AGE VERSION
docker-desktop Ready control-plane,master 2d11h v1.22.5