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..
Related
I have a single master cluster with 3 worker nodes. The master node has one network interface of 10Gb capacity and all worker nodes have a 40Gb interface. They are all connected via a switch.
I'd like to know if this might create a bottleneck if the data between nodes have to pass through the master node?
In general, I like to understand the communication flow between worker nodes. For instance, a pod in node1 sends data to a pod in node2, does the traffic go through the master node? I have seen the architecture diagram on the Kubernetes docs and it appears to be the case:
source: https://kubernetes.io/docs/concepts/overview/components/
If this is the case, it is possible to define a control plane network separate from the data plane by possibly adding another interface to worker nodes?
Please note that this is a bare-metal on-prem installation with OSS Kubernetes v1.20.
For instance, a pod in node1 sends data to a pod in node2, does the traffic go through the master node?
No. Kubernetes is designed with a flat network model. If Pod on node A send a request to Pod on node B, the inter-node traffic is directly from node A to node B as they are on the same IP network.
See also The Kubernetes network model
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.
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 been reading for several days about how to deploy a Kubernetes cluster from scratch. It's all ok until it comes to etcd.
I want to deploy the etcd nodes inside the Kubernetes cluster. It looks there are many options, like etcd-operator (https://github.com/coreos/etcd-operator).
But, to my knowledge, a StatefulSet or a ReplicaSet makes use of a etcd.
So, what is the right way to deploy such a cluster?
My first thought: start with a single member etcd, either as a pod or a local service in the master node and, when the Kubernetes cluster is up, deploy the etcd StatefulSet and move/change/migate the initial etcd to the new cluster.
The last part sounds weird to me: "and move/change/migate the initial etcd to the new cluster."
Am I wrong with this approach?
I don't find useful information on this topic.
Kubernetes has 3 components: master components, node components and addons.
Master components
kube-apiserver
etcd
kube-scheduler
kube-controller-manager/cloud-controller-manager
Node components
kubelet
kube-proxy
Container Runtime
While implementing Kubernetes yu have to implement etcd as part of it. If it is multi node architecture you can use independent node or along with master node as per your requirement. You can find more details here. If you are looking for step by step guide follow this document if you need multi node architecture. If you need single node Kubernetes go for minikube.
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