[K8S series] k8s learning two, kubernetes core concepts and preliminary understanding of installation and deployment methods

Let’s review K8S cluster architecture, and find a cluster architecture diagram on the Internet to illustrate the wave

1. The master component

• apiserver

Unified entrance of the cluster, restful way, and finally handed over to etcd storage

• shcheduler

Node scheduling, select node node for application deployment

• controller-manager

Handle regular background tasks in the cluster, one resource corresponds to one controller

• etcd

Storage system, used to store cluster-related data

2. Node component, working node

• kubelet

The master is arranged to the node representative to manage the container of the machine

• kube-proxy

Provide network proxy, load balancing and other operations

k8s core concept

1、Pod

• Minimal deployment logic unit
• Is a collection of containers
• Shared network
• Short life cycle

2、controller

• Ensure the expected number of Pod copies
• Stateless application deployment / Stateful application deployment
• Ensure that all nodes run the same Pod
• Perform one-time tasks and timed tasks

3、service

• Define a set of Pod access rules

Kubernetes installation method:

• Use the official minikube
• Use kubeadmin for deployment. The k8s deployment tool runs in k8s. This is relatively simple to use

kubeadmin provides kubeadmin init and kubeadmin join for rapid deployment of k8s cluster

The official website address is: https://kubernetes.io/docs/reference/setup-tools/kubeadm/

• Use the kubernetes binary method to install and deploy by yourself (this deployment method, we must take this step when we learn, and build it step by step, so that we can encounter many problems, and then solve him and become familiar with him)

Official minikube

minikube

Click Launch Terminal, you can see the following interface

The official version of minikube provided to us is v1.8.1

The system is Ubuntu 18.04

CPU 2 core

RAM 2 G

Disk around 145 G

Kubernetes version v1.17.6

Docker version 19.03.

We can use kubectl get pods -n kube-system check the pod node

kubeadmin for deployment

Use kubeadmin to deploy, it is simpler and easier than using binary to deploy. Let's plan the deployment plan first.

Platform Planning

Single master construction method

Multi-master construction method

kubeadmin began to deploy

Use kubeadmin to deploy the k8s environment, and complete the deployment of kubernetes through the following two instructions:

• kubeadm init

Create a master node

• kubeadm join <IP and port of master node>

Add the node node to the cluster

test environment hardware requirements

master node: 2 cores, 2G, disk 20G

node node: 4 cores, 8G, disk 80G

• One or more machines, the operating system is optional, it can be ubuntu or centos
• The hardware configuration is as above
• All nodes in the cluster communicate with each other
• Can access the external network, can pull the mirror image
• Prohibit swap partition

first install kubectl

The official provides 4 ways to install kubecrl

• Use curl to install kubectl in Linux system
• mounting native package management tool
• with other package management tools installed
• part of Google Cloud SDK, install

Let's use the first type directly:

1. Use the following command to download the latest version of kubectl

curl -LO "https://dl.k8s.io/release/$(curl -L -s https://dl.k8s.io/release/stable.txt)/bin/linux/amd64/kubectl"

2. Download the kubectl checksum file

curl -LO "https://dl.k8s.io/$(curl -L -s https://dl.k8s.io/release/stable.txt)/bin/linux/amd64/kubectl.sha256"

3. Verify the executable file of kubectl

echo "$(<kubectl.sha256) kubectl" | sha256sum --check

# echo "$(<kubectl.sha256) kubectl" | sha256sum --check
kubectl: OK

In the above situation, in order to pass the verification

4. Install kubectl

sudo install -o root -g root -m 0755 kubectl /usr/local/bin/kubectl

5. Check the version we installed

kubectl version --client

# kubectl version --client
Client Version: version.Info{Major:"1", Minor:"22", GitVersion:"v1.22.0", GitCommit:"c2b5237ccd9c0f1d600d3072634ca66cefdf272f", GitTreeState:"clean", BuildDate:"2021-08-04T18:03:20Z", GoVersion:"go1.16.6", Compiler:"gc", Platform:"linux/amd64"}

• GitVersion

The version of git is v1.22.0

• GoVersion

The version of go is 1.16.6

• BuildDate

The build time is 2021-08-04T18:03, which is fairly new

Configure kubectl auto-completion function

The auto-completion function of kubectl relies on bash-completion, so we need to install it

1. Install bash-completion

apt-get install bash-completion

2. Start kubectl auto-completion function

Import (source) the completion script in ~/.bashrc

echo 'source <(kubectl completion bash)' >>~/.bashrc

Add the completion script to the directory /etc/bash_completion.d

kubectl completion bash >/etc/bash_completion.d/kubectl

If kubectl has an associated alias, you can extend the shell completion to adapt this alias

echo 'alias k=kubectl' >>~/.bashrc
echo 'complete -F __start_kubectl k' >>~/.bashrc

The installation and deployment method of kubernetes has a lot of steps. This must be practiced step by step by yourself, otherwise you will not be able to learn anything. You can find more on the official website.

https://kubernetes.io/docs/tasks/tools/install-kubectl-linux/

Reference materials:

kubernetes docs

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