在一个CentOS8系统的VPS上，free显示不对，有1G内存但是只显示了818MB，少了200多MB

              total        used        free      shared  buff/cache   available
Mem:            818          87         453           7         277         597
Swap:          1023           0        1023

1、使用dmidecode命令查看linux硬件信息
dmidecode -t memory

# dmidecode 3.2
Getting SMBIOS data from sysfs.
SMBIOS 2.8 present.

Handle 0x1000, DMI type 16, 23 bytes
Physical Memory Array
	Location: Other
	Use: System Memory
	Error Correction Type: Multi-bit ECC
	Maximum Capacity: 1 GB
	Error Information Handle: Not Provided
	Number Of Devices: 1

Handle 0x1100, DMI type 17, 40 bytes
Memory Device
	Array Handle: 0x1000
	Error Information Handle: Not Provided
	Total Width: Unknown
	Data Width: Unknown
	Size: 1 GB
	Form Factor: DIMM
	Set: None
	Locator: DIMM 0
	Bank Locator: Not Specified
	Type: RAM
	Type Detail: Other
	Speed: Unknown
	Manufacturer: Red Hat
	Serial Number: Not Specified
	Asset Tag: Not Specified
	Part Number: Not Specified
	Rank: Unknown
	Configured Memory Speed: Unknown
	Minimum Voltage: Unknown
	Maximum Voltage: Unknown
	Configured Voltage: Unknown

以修改tomcat版本号为例

1、直接编辑文件（vi命令是乱码）
vim catalina.jar

2、搜索或光标移动到ServerInfo.properties，按回车

3、修改版本号，正常保存退出即可
server.info=Apache Tomcat/1.1.1
server.number=1.1.1.1

Helm是用来管理Kubernetes发布包的工具，使用方法类似于yum、npm工具
原来：手写yaml –> xxx.yaml –> kubectl apply -f –> 获取xxx组件
现在：values.yaml –> 通过模板生成xxx.yaml –> helm install/upgrade –> 获取xxx组件

PS：以下操作都在master机器上
1、安装Helm3
Helm3.x版本移除了tiller依赖，所以只有一个helm文件
cd /tmp
wget https://get.helm.sh/helm-v3.4.0-linux-amd64.tar.gz
tar -zxvf helm-v3.4.0-linux-amd64.tar.gz
mv linux-amd64/helm /usr/local/bin/helm

2、配置环境变量
vi /etc/profile
加入：
export KUBECONFIG=/root/.kube/config
执行：
source /etc/profile

1、在node1和node2执行
kubeadm join 192.168.101.1:6443 --token mu949z.xkhkw4tq7t79z4v6 \
--discovery-token-ca-cert-hash sha256:0a381d7f750bda8d639b7132bf4db942710d2042b2cef0c6ffe6aa49a4603f5d \
--ignore-preflight-errors=Swap

2、返回
W0713 04:55:55.810886 12707 join.go:346] [preflight] WARNING: JoinControlPane.controlPlane settings will be ignored when control-plane flag is not set.
[preflight] Running pre-flight checks
[WARNING Swap]: running with swap on is not supported. Please disable swap
error execution phase preflight: couldn't validate the identity of the API Server: could not find a JWS signature in the cluster-info ConfigMap for token ID "mu949z"
To see the stack trace of this error execute with --v=5 or higher

1、安装flannel network（主节点）
cd ~
wget https://raw.githubusercontent.com/coreos/flannel/master/Documentation/kube-flannel.yml
kubectl apply -f kube-flannel.yml

podsecuritypolicy.policy/psp.flannel.unprivileged created
clusterrole.rbac.authorization.k8s.io/flannel created
clusterrolebinding.rbac.authorization.k8s.io/flannel created
serviceaccount/flannel created
configmap/kube-flannel-cfg created
daemonset.apps/kube-flannel-ds-amd64 created
daemonset.apps/kube-flannel-ds-arm64 created
daemonset.apps/kube-flannel-ds-arm created
daemonset.apps/kube-flannel-ds-ppc64le created
daemonset.apps/kube-flannel-ds-s390x created

2、pod概念
pod是k8s最小管理单位，它是一个或多个容器的组合

3、flannel network
用于集群中各个pod互相通讯的网络，Kubernetes支持Flannel、Calico、Weave network等多种cni网络Drivers
此时执行docker images，会看到多了一个flannel的镜像：
quay.io/coreos/flannel

4、查看集群节点状态，变为Ready
kubectl get nodes

NAME STATUS ROLES AGE VERSION
k8s-master Ready master 2d21h v1.18.5

三、创建单个控制面板（主节点）集群
1、初始化主节点
由于测试环境原因，忽略一些错误
kubeadm init --pod-network-cidr=10.122.0.0/16 \
--ignore-preflight-errors=Swap

参数说明：
--apiserver-advertise-address：指定用master的哪个IP地址与cluster的其他节点通信
--service-cidr：指定service网络的范围，即负载均衡VIP使用的IP地址段
--pod-network-cidr：指定pod网络的范围，即pod的IP地址段
--ignore-preflight-errors=：忽略运行时的错误

2、如果初始化失败，查看原因
systemctl status kubelet
journalctl -xeu kubelet
重置：
systemctl stop kubelet
kubeadm reset
systemctl daemon-reload

一、环境准备（所有节点）
1、节点信息
k8s-master：192.168.101.1
k8s-node1：192.168.101.2
k8s-node2：192.168.101.3

2、系统信息
CentOS Linux release 7.8.2003 (Core)

3、关闭selinux
sed -i 's/enforcing/disabled/' /etc/selinux/config
setenforce 0

4、关闭防火墙
systemctl stop firewalld
systemctl disable firewalld

5、关闭swap（测试环境可不关闭）
vi /etc/fstab
去除swap配置，并reboot
PS：为了应用发生OOM时，使其被系统kill掉，及时发现问题

6、设置主机名和hosts
主节点：k8s-master
工作节点1：k8s-node1
工作节点2：k8s-node2
vi /etc/hosts
1）k8s-master节点
127.0.0.1 k8s-master
192.168.101.2 k8s-node1
192.168.101.3 k8s-node2
2）k8s-node1节点
127.0.0.1 k8s-node1
192.168.101.1 k8s-master
192.168.101.3 k8s-node2
3）k8s-node2节点
127.0.0.1 k8s-node2
192.168.101.1 k8s-master
192.168.101.2 k8s-node1