I started a minikube cluster (single node cluster) on my local machine with the command:
minikube start --driver=virtualbox
Now, when I execute the command:
kubectl get nodes
it returns:
NAME STATUS ROLES AGE VERSION
minikube Ready master 2m59s v1.19.0
My question is: since the cluster has only one node and according to the previous command it is a master node, what is the worker node? Are the master and worker nodes the same node in case of a single node cluster?
The answer to your question is yes in your case your master node is itself a worker node.
Cluster The group of vm or physical computers.
Master is the where control plane component installed such as etcd,controller-manager,api-server which are necessary to control the whole cluster state. In best practices and big production cluster never ever use master node to schedule application related workload.
Worker node is the simple plane VM where docker and kubernetes packages installed but not installed the control-plane component etc. Normally worker node is used to handle your application related workload.
And if you have only one machine where you configure kubernetes then it becomes single node kubernetes. and it act as a master/worker.
I hope this helps you to unsderstand
since the cluster has only one node and according to the previous command it is a master node, what is the worker node? Are the master and worker nodes the same node in case of a single node cluster?
Yes, using Minikube, you only use a single node. And your workload is scheduled to execute on the same node.
Typically, Taints and Tolerations is used on master nodes to prevent workload to be scheduled to those nodes.
Related
Cluster consists of one master and one worker node. If the master is down and worker is restarted no workloads (deployments) are started on boot. How and if it is possible to make worker resume last state without master?
Kubernetes 1.18.3
On worker node are installed: kubelet, kubectl, kubeadm
Ideally you should have more than one(typically a odd number like 3 or 5) node serving as master and accessible from worker nodes via a LoadBalancer.
The state is stored in ETCD which is accessed by worker nodes via the API Server. So without master nodes running there is no way for workers to know the desired state.
Although it's not recommended you but can use static pod as potential solution here.Static Pods are managed directly by the kubelet daemon on a specific node, without the API server observing them.Unlike Pods that are managed by the control plane (for example, a Deployment ), instead the kubelet watches each static Pod (and restarts it if it crashes).
The caveat of using static pod is since those pods are not dependent on API Server Hence static Pods cannot be managed with kubectl or other Kubernetes API clients.
I have two IP'S master node and worker node? I need to deploy some services using these. I don't know anything about kubernetes ,what is master node and worker node?
How do I start?
You should start from the very basic things..
Kubernetes concept page is your starting point.
The Kubernetes Master is a collection of three processes that run on a
single node in your cluster, which is designated as the master node.
Those processes are: kube-apiserver, kube-controller-manager and
kube-scheduler.
Each individual non-master node in your cluster runs
two processes: kubelet, which communicates with the Kubernetes Master.
kube-proxy, a network proxy which reflects Kubernetes networking
services on each node.
Regarding you question in comment: read Organizing Cluster Access Using kubeconfig Files. Make sure you have kubeconfig file in the right place..
I deployed Kubernetes with multiple master configuration from kubadm multiple maser HA document. Then I join a worker node to this cluster.
At worker node, I could not ping ip of pods which were running at other nodes.
At each master node, I could ping other node's pods.
I also found that the cni0 interface not existed at worker nodes but existed at master nodes.
Did I miss any configurations?
Any suggestions will be appreciated.
I have kubernetes running on version 1.5 with two nodes and one master nodes. I would like to deploy fluentd as a daemon set onto all nodes, but the master node (the master node spams warning messages as it can't find logs). How can I avoid deploying to the master node?
So to make a pod not schedule on a master node you need to add the following
nodeSelector:
kubernetes.io/role: node
This will make the pod schedule on only nodes. The above example shows the default label for node in kops provisioned cluster. Please very the key value if you have have provisioned the cluster from a different provider
You can use a label for your slave nodes and use that label in a selector for the daemon set, which will only deploy on the nodes that have that label.
Inversely, you can define a negative selector to assign the daemon set to pods that don't have a label. In your case, the pod that doesn't have the master's label.
You're looking for the Taints and Tolerations features. Using these you can define that given node in "tainted" in particular way preventing pods scheduling on this node unless they have a toleration matching that taint.
http://kubernetes.io/docs/getting-started-guides/centos/centos_manual_config/
"This guide will only get ONE node working. Multiple nodes requires a functional networking configuration done outside of kubernetes."
So, is a node made up of many hosts?
I thought cluster is made up of many hosts. Is the cluster made up of many nodes instead?
Each node had a master and minions so a cluster has more than one master?
Host: some machine (physical or virtual)
Master: a host running Kubernetes API server and other master systems
Node: a host running kubelet + kube-proxy that pods can be scheduled onto
Cluster: a collection of one or masters + one or more nodes