I'm trying to understand how kubernetes works, so I tried to do this operation for my minikube:
~ kubectl delete pod --all -n kube-system
pod "coredns-f9fd979d6-5n4b6" deleted
pod "etcd-minikube" deleted
pod "kube-apiserver-minikube" deleted
pod "kube-controller-manager-minikube" deleted
pod "kube-proxy-879lg" deleted
pod "kube-scheduler-minikube" deleted
It's okay. Pods deleted as wish. But if I do kubectl get pods -n kube-system I will see:
NAME READY STATUS RESTARTS AGE
coredns-f9fd979d6-5d25r 1/1 Running 0 50s
etcd-minikube 1/1 Running 0 50s
kube-apiserver-minikube 1/1 Running 0 50s
kube-controller-manager-minikube 1/1 Running 0 50s
kube-proxy-nlw69 1/1 Running 0 43s
kube-scheduler-minikube 1/1 Running 0 49s
Okay. I thought it's ReplicaSet or DaemonSet:
➜ ~ kubectl get ds -n kube-system
NAME DESIRED CURRENT READY UP-TO-DATE AVAILABLE NODE SELECTOR AGE
kube-proxy 1 1 1 1 1 kubernetes.io/os=linux 18m
➜ ~ kubectl get rs -n kube-system
NAME DESIRED CURRENT READY AGE
coredns-f9fd979d6 1 1 1 18m
It is true for coredns and kube-proxy. But what about others (apiserver, etcd, controller and scheduler)? Why are they still alive?
The control plane pods are run as static Pods - static Pods are not managed by the control plane controllers like e.g. DaemonSet and ReplicaSet. Static pods are instead managed by the Kubelet daemon on the local node directly.
Related
I'm trying to delete some old deployments / replicasets I have in my cluster but when I run kubectl delete deployment
It'll say the deployment is deleted and the pod from that deployment is Terminating, but then a few seconds later the deployment is magically recreated and the pod comes back.
This is the same result for another replicaset I have.
What could be re-creating these deployments / replicasets and how can I stop it so I can permanently delete these deployments/rs?
Edit: Here's some output. This is on a kubernetes cluster in GKE btw:
kubectl get deployments
NAME READY UP-TO-DATE AVAILABLE AGE
quickstart-kb 1/1 1 1 41m
ubuntu 1/1 1 1 66d
kubectl get pods
NAME READY STATUS RESTARTS AGE
ubuntu-677fc9fd77-fgd7k 1/1 Running 0 19d
quickstart-kb-f9b65577f-4fxph 1/1 Running 0 40m
kubectl delete deployment quickstart-kb
deployment.extensions "quickstart-kb" deleted
kubectl get deployments
NAME READY UP-TO-DATE AVAILABLE AGE
quickstart-kb 0/1 1 0 7s
ubuntu 1/1 1 1 66d
kubectl get pods
NAME READY STATUS RESTARTS AGE
quickstart-kb-6cb6cf897d-qcjff 0/1 Running 0 11s
ubuntu-677fc9fd77-fgd7k 1/1 Running 0 19d
kubectl get deployments
NAME READY UP-TO-DATE AVAILABLE AGE
quickstart-kb 1/1 1 1 4m6s
ubuntu 1/1 1 1 66d
kubectl get pods
NAME READY STATUS RESTARTS AGE
quickstart-kb-6cb6cf897d-qcjff 1/1 Running 0 4m13s
ubuntu-677fc9fd77-fgd7k 1/1 Running 0 19d
I think your deployment object is created with the deployment of some custom resources (CRD).
When you created the CRD, the CRD controller created the deployment object. So, even if you delete the deployment object, the CRD controller re-creates it.
Delete the CRD object itself, to delete the deployment and other objects (if any) that were created with it.
From the name, it seems like Kibana CRD object:
apiVersion: kibana.k8s.elastic.co/v1
kind: Kibana
Use the following command to delete the Kibana object:
$ kubectl delete Kibana quickstart-kb
How do you list components running on the master Kubernetes node?
I assume there should be a kubeadm or kubectl command but can't find anything.
E.g. I'm looking to see if the Scheduler is running and I've used kubeadm config view which lists:
scheduler: {}
but not sure if that means the Scheduler is not running or there's simply no config for it.
Since you have installed with kubeadm, the control plane components must be running as pods in kube-system namespace. So you can run the following command to see if scheduler is running.
# kubectl get pod -n kube-system
NAME READY STATUS RESTARTS AGE
calico-node-4x9fp 2/2 Running 0 4d6h
coredns-86c58d9df4-bw2q9 1/1 Running 0 4d6h
coredns-86c58d9df4-gvcl9 1/1 Running 0 4d6h
etcd-k1 1/1 Running 0 4d6h
kube-apiserver-k1 1/1 Running 0 4d6h
kube-controller-manager-k1 1/1 Running 83 4d6h
kube-dash-kubernetes-dashboard-5b7cf769bc-pd2n2 1/1 Running 0 4d6h
kube-proxy-jmrrz 1/1 Running 0 4d6h
kube-scheduler-k1 1/1 Running 82 4d6h
metrics-server-8544b5c78b-k2lwt 1/1 Running 16 4d6h
tiller-deploy-5f4fc5bcc6-gvhlz 1/1 Running 0 4d6h
If you want to know all pods running on a master node(or any particular node), you can use field-selector to select the node.
kubectl get pod --all-namespaces --field-selector spec.nodeName=<nodeName>
To filter pods only in kube-system namespace running on particular node -
kubectl get pod -n kube-system --field-selector spec.nodeName=<nodeName>
Assuming that you want to check what is running in master node and you are unable not do that via Kubernetes API server.
For kubelet since its running as systemd service you can check systemctl status kubelet.service.
Other components such as scheduler is run as container by kubelet so you can check them with standard docker command such as docker ps.
I am building a Kubernetes cluster following this tutorial, and I have troubles to access the Kubernetes dashboard. I already created another question about it that you can see here, but while digging up into my cluster, I think that the problem might be somewhere else and that's why I create a new question.
I start my master, by running the following commands:
> kubeadm reset
> kubeadm init --apiserver-advertise-address=[MASTER_IP] > file.txt
> tail -2 file.txt > join.sh # I keep this file for later
> kubectl apply -f https://git.io/weave-kube/
> kubectl -n kube-system get pod
NAME READY STATUS RESTARTS AGE
coredns-fb8b8dccf-kb2zq 0/1 Pending 0 2m46s
coredns-fb8b8dccf-nnc5n 0/1 Pending 0 2m46s
etcd-kubemaster 1/1 Running 0 93s
kube-apiserver-kubemaster 1/1 Running 0 93s
kube-controller-manager-kubemaster 1/1 Running 0 113s
kube-proxy-lxhvs 1/1 Running 0 2m46s
kube-scheduler-kubemaster 1/1 Running 0 93s
Here we can see that I have two coredns pods stuck in Pending state forever, and when I run the command :
> kubectl -n kube-system describe pod coredns-fb8b8dccf-kb2zq
I can see in the Events part the following Warning :
Failed Scheduling : 0/1 nodes are available 1 node(s) had taints that the pod didn't tolerate.
Since it is a Warning and not and Error, and that as a Kubernetes newbie, taints does not mean much to me, I tried to connect a node to the master (using the previously saved command) :
> cat join.sh
kubeadm join [MASTER_IP]:6443 --token [TOKEN] \
--discovery-token-ca-cert-hash sha256:[ANOTHER_TOKEN]
> ssh [USER]#[WORKER_IP] 'bash' < join.sh
This node has joined the cluster.
On the master, I check that the node is connected:
> kubectl get nodes
NAME STATUS ROLES AGE VERSION
kubemaster NotReady master 13m v1.14.1
kubeslave1 NotReady <none> 31s v1.14.1
And I check my pods :
> kubectl -n kube-system get pod
NAME READY STATUS RESTARTS AGE
coredns-fb8b8dccf-kb2zq 0/1 Pending 0 14m
coredns-fb8b8dccf-nnc5n 0/1 Pending 0 14m
etcd-kubemaster 1/1 Running 0 13m
kube-apiserver-kubemaster 1/1 Running 0 13m
kube-controller-manager-kubemaster 1/1 Running 0 13m
kube-proxy-lxhvs 1/1 Running 0 14m
kube-proxy-xllx4 0/1 ContainerCreating 0 2m16s
kube-scheduler-kubemaster 1/1 Running 0 13m
We can see that another kube-proxy pod have been created and is stuck in ContainerCreating status.
And when I am doing a describe again :
kubectl -n kube-system describe pod kube-proxy-xllx4
I can see in the Events part multiple identical Warnings :
Failed create pod sandbox : rpx error: code = Unknown desc = failed pulling image "k8s.gcr.io/pause:3.1": Get https://k8s.gcr.io/v1/_ping: dial tcp: lookup k8s.gcr.io on [::1]:53 read up [::1]43133->[::1]:53: read: connection refused
Here are my repositories :
docker image ls
REPOSITORY TAG
k8s.gcr.io/kube-proxy v1.14.1
k8s.gcr.io/kube-apiserver v1.14.1
k8s.gcr.io/kube-controller-manager v1.14.1
k8s.gcr.io/kube-scheduler v1.14.1
k8s.gcr.io/coredns 1.3.1
k8s.gcr.io/etcd 3.3.10
k8s.gcr.io/pause 3.1
And so, for the dashboard part, I tried to start it with the command
> kubectl apply -f https://raw.githubusercontent.com/kubernetes/dashboard/master/aio/deploy/recommended/kubernetes-dashboard.yaml
But the dashboard pod is stuck in Pending state.
kubectl -n kube-system get pod
NAME READY STATUS RESTARTS AGE
coredns-fb8b8dccf-kb2zq 0/1 Pending 0 40m
coredns-fb8b8dccf-nnc5n 0/1 Pending 0 40m
etcd-kubemaster 1/1 Running 0 38m
kube-apiserver-kubemaster 1/1 Running 0 38m
kube-controller-manager-kubemaster 1/1 Running 0 39m
kube-proxy-lxhvs 1/1 Running 0 40m
kube-proxy-xllx4 0/1 ContainerCreating 0 27m
kube-scheduler-kubemaster 1/1 Running 0 38m
kubernetes-dashboard-5f7b999d65-qn8qn 1/1 Pending 0 8s
So, event though my problem originaly was that I cannot access to my dashboard, I guess that the real problem is deeper thant that.
I know that I just put a lot of information here, but I am a k8s beginner and I am completely lost on this.
There is an issue I experienced with coredns pods stuck in a pending mode when setting up your own cluster; which I resolve by adding pod network.
Looks like because there is no Network Addon installed, the nodes are taint as not-ready. Installing the Addon would remove the taints and the Pods will be able to schedule. In my case adding flannel fixed the issue.
EDIT: There is a note about this in the official k8s documentation - Create cluster with kubeadm:
The network must be deployed before any applications. Also, CoreDNS
will not start up before a network is installed. kubeadm only
supports Container Network Interface (CNI) based networks (and does
not support kubenet).
Actually it is the opposite of a deep or serious issue. This is a trivial issue. Always you see a pod stuck on Pending state, it means the scheduler is having a hard time to schedule the pod; mostly because there are no enough resources on the node.
In your case it is a taint that has the node, and your pod doesn't have the toleration. What you have to do is to describe the node and get the taint:
kubectl describe node | grep -i taints
Note: you might have more then one taint. So you might want to do kubectl describe no NODE since with grep you will only see one taint.
Once you get the taint, that will be something like hello=world:NoSchedule; which means key=value:effect, you will have to add a toleration section in your Deployment. This is an example Deployment so you can see how it should look like:
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
name: nginx
labels:
app: nginx
spec:
replicas: 10
strategy:
type: Recreate
template:
metadata:
labels:
app: nginx
spec:
containers:
- image: nginx
name: nginx
ports:
- containerPort: 80
name: http
tolerations:
- effect: NoExecute #NoSchedule, PreferNoSchedule
key: node
operator: Equal
value: not-ready
tolerationSeconds: 3600
As you can see there is the toleration section in the yaml. So, if I would have a node with node=not-ready:NoExecute taint, no pod would be able to be scheduled on that node, unless would have this toleration.
Also you can remove the taint, if you don need it. To remove a taint you would describe the node, get the key of the taint and do:
kubectl taint node NODE key-
Hope it makes sense. Just add this section to your deployment, and it will work.
Set up the flannel network tool.
Running commands:
$ sysctl net.bridge.bridge-nf-call-iptables=1
$ kubectl apply -f
https://raw.githubusercontent.com/coreos/flannel/62e44c867a2846fefb68bd5f178daf4da3095ccb/Documentation/kube-flannel.yml
I followed the guide on "Using kubeadm to Create a Cluster" but I am not able to view logs using kubectl:
root#o1:~# kubectl logs -n kube-system etcd-o1
Error from server: Get https://149.156.11.4:10250/containerLogs/kube-system/etcd-o1/etcd: tls: first record does not look like a TLS handshake
The above IP address is the cloud frontend address not the address of the VM which probably causes the problem. Some other kubectl cmds seem to work:
root#o1:~# kubectl cluster-info
Kubernetes master is running at https://10.6.16.88:6443
KubeDNS is running at https://10.6.16.88:6443/api/v1/namespaces/kube-system/services/kube-dns/proxy
To further debug and diagnose cluster problems, use 'kubectl cluster-info dump'.
root#o1:~# kubectl get pods --all-namespaces
NAMESPACE NAME READY STATUS RESTARTS AGE
kube-system etcd-o1 1/1 Running 0 3h
kube-system kube-apiserver-o1 1/1 Running 0 3h
kube-system kube-controller-manager-o1 1/1 Running 0 3h
kube-system kube-dns-545bc4bfd4-mhbfb 3/3 Running 0 3h
kube-system kube-flannel-ds-lw87h 2/2 Running 0 1h
kube-system kube-flannel-ds-rkqxg 2/2 Running 2 1h
kube-system kube-proxy-hnhfs 1/1 Running 0 3h
kube-system kube-proxy-qql4r 1/1 Running 0 1h
kube-system kube-scheduler-o1 1/1 Running 0 3h
Please help.
Maybe change the address in the $HOME/admin.conf.
This is a really odd issue I've started to experience. Everything was working with out issue, however, now when I startup a cluster (kubeadm), setup flannel, kube-dns never starts up. Eventually, it errors out with the following output from kubectl describe
Error: failed to start container "sidecar": Error response from daemon: {"message":"invalid header field value \"oci runtime error: container_linux.go:240: creating new parent process caused \\\"container_linux.go:1245: running lstat on namespace path \\\\\\\"/proc/7420/ns/ipc\\\\\\\" caused \\\\\\\"lstat /proc/7420/ns/ipc: no such file or directory\\\\\\\"\\\"\\n\""}
Any ideas what this error really means? I get the same looking error for dnsmasq and kubedns as well.
I am using the switch "--pod-network-cidr 10.244.0.0/16" as always. As I said ,this was working, and then a few days later, it's not....
Here's the get pods output:
NAMESPACE NAME READY STATUS RESTARTS AGE
kube-system etcd-machiato-0 1/1 Running 0 3m
kube-system kube-apiserver-machiato-0 1/1 Running 0 3m
kube-system kube-controller-manager-machiato-0 1/1 Running 0 2m
kube-system kube-dns-2258483030-pd8qj 0/3 ContainerCreating 0 3m
kube-system kube-flannel-ds-0z0dd 2/2 Running 0 1m
kube-system kube-flannel-ds-3dccg 2/2 Running 0 1m
kube-system kube-proxy-gc8ft 1/1 Running 0 3m
kube-system kube-proxy-tjgzn 1/1 Running 0 1m
kube-system kube-scheduler-machiato-0 1/1 Running 0 3m
Eventually, "ContainerCreating" switches to "CrashLoopBackOff" then I see the lstat error above.
most likely its overlay network issue. can you check the dns pods log message and see any error message?
kubectl logs -n kube-system kube-dns-2258483030-pd8qj -c kubedns
kubectl logs -n kube-system kube-dns-2258483030-pd8qj -c dnsmasq
kubectl logs -n kube-system kube-dns-2258483030-pd8qj -c sidecar