kubernetes 实验环境搭建

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都 2021 年了，我终于把 kubernetes 实验测试环境搭建好了，泪目

2019 年的时候，我也曾经尝试学习，搭建 kubernetes 集群，结果当时自己的电脑性能太差了。一台 mac 模拟出三台虚拟机，性能上根本无法满足要求，甚至偶尔死机。还有当时自己 naive， 也不会善用快照, 每次搞崩溃了环境，又重头再来，费时费力。

如今，时代变了。兵强马壮，家里有三台笔记本，一台台式机，机荒的日子已经一去不复返了。重现当年好学的荣光，我辈义不容辞，冲。

概要

本文记录了，在三台 Ubuntu 虚拟机上搭建一个 kubernetes 集群的全部过程，以及分享菜鸡我踩过的坑。

实验的环境如下， 都是 Ubuntu desktop 桌面版的，我也建议用桌面版。 原因：比如 kubernetes Dashboard 只能从 localhost 本地访问，桌面版自带 Firefox 浏览器，就可以直接在虚拟机界面里面直接操作， 少一步转发。

Name Operating system Kernel CPU RAM Disk IP
ubuntu18-119 Ubuntu 18.04.5 LTS 5.4.0 2 4G 30G 192.168.1.119
ubuntu18-120 Ubuntu 18.04.5 LTS 5.4.0 2 4G 30G 192.168.1.120
ubuntu18-121 Ubuntu 18.04.5 LTS 5.4.0 2 4G 30G 192.168.1.121

这三台虚拟机，分别跑在三台笔记本电脑上。这样做的好处是，桥接模式不需要 NAT 端口映射，在我家的局域网里面尽情的玩耍。
当然如果你的电脑性能超级好，一台物理机跑三台虚拟机也是没有问题的。

实验环境的搭建，可以参考我的另外一篇博客 https://feiyang233.club/post/vm/

搭建集群

分享两个不错的参考文档：

准备工作

在每一台机器上面做相同的准备工作。

硬件要求

  • 每台机器 2 GB 或更多的 RAM
  • 2 CPU 核或更多
  • 集群中的所有机器的网络彼此均能相互连接

  • 节点之中不可以有重复的主机名、MAC 地址或 product_uuid

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    你可以使用命令 ip link 或 ifconfig -a 来获取网络接口的 MAC 地址
    可以使用 sudo cat /sys/class/dmi/id/product_uuid 命令对 product_uuid 校验

  • 禁用交换分区。 删除文件 /etc/fstab 中 swapfile 一行

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    # /etc/fstab: static file system information.
    #
    # Use 'blkid' to print the universally unique identifier for a
    # device; this may be used with UUID= as a more robust way to name devices
    # that works even if disks are added and removed. See fstab(5).
    #
    # <file system> <mount point>   <type>  <options>       <dump>  <pass>
    # / was on /dev/sda1 during installation
    UUID=2bd16ba3-1087-4d5e-9d1b-f1527f62a3ce /               ext4    errors=remount-ro 0       1
    # /swapfile                                 none            swap    sw              0       0
    /dev/fd0        /media/floppy0  auto    rw,user,noauto,exec,utf8 0       0
  • 允许 iptables 检查桥接流量
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    root@ubuntu18-121:~# lsmod | grep br_netfilter
    br_netfilter           28672  0
    bridge                176128  1 br_netfilter
    root@ubuntu18-121:~# sudo modprobe br_netfilter
  • 禁用默认的防火墙服务, Ubuntu和Debian等Linux发行版默认使用ufw（Uncomplicated FireWall）作为前端来简化 iptables的使用
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    ufw disable

    ufw status

安装 docker

参考官网文档

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sudo apt-get update

sudo apt-get install \
    apt-transport-https \
    ca-certificates \
    curl \
    gnupg \
    lsb-release

curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo gpg --dearmor -o /usr/share/keyrings/docker-archive-keyring.gpg

echo \
  "deb [arch=amd64 signed-by=/usr/share/keyrings/docker-archive-keyring.gpg] https://download.docker.com/linux/ubuntu \
  $(lsb_release -cs) stable" | sudo tee /etc/apt/sources.list.d/docker.list > /dev/null

sudo apt-get update

sudo apt-get install docker-ce docker-ce-cli containerd.io

Container runtimes

配置 Docker 守护程序，尤其是使用 systemd 来管理容器的 cgroup。
参考： https://kubernetes.io/zh/docs/setup/production-environment/container-runtimes/#docker

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cat <<EOF | sudo tee /etc/docker/daemon.json
{
  "exec-opts": ["native.cgroupdriver=systemd"],
  "log-driver": "json-file",
  "log-opts": {
    "max-size": "100m"
  },
  "storage-driver": "overlay2"
}
EOF


sudo systemctl enable docker
sudo systemctl daemon-reload
sudo systemctl restart docker

设置集群

在三台机器上面安装 kubelet kubeadm kubectl，我当时安装的版本是 v1.21.1

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sudo apt-get update && sudo apt-get install -y apt-transport-https gnupg2 curl

curl -s https://packages.cloud.google.com/apt/doc/apt-key.gpg | sudo apt-key add -

echo "deb https://apt.kubernetes.io/ kubernetes-xenial main" | sudo tee -a /etc/apt/sources.list.d/kubernetes.list

sudo apt-get update

sudo apt-get install -y kubelet kubeadm kubectl

#  运行如下命令单独获取相关的镜像文件, 加速后面的 init 
kubeadm config images pull

到这来就可以先把三台机器关机，然后备份，存快照 snapshot

master

初始化master节点，kubeadm init命令支持两种初始化方式，一是通过命令行选项传递关键的部署设定，另一个是基于yaml格式的专用配置文件，后一种允许用户自定义各个部署参数。

命令中的各选项简单说明如下：

  • –pod-network-cidr：Pod网络的地址范围，其值为CIDR格式的网络地址，通常，Flannel网络插件的默认为10.244.0.0/16，Project Calico插件的默认值为192.168.0.0/16；
  • –service-cidr：Service的网络地址范围，其值为CIDR格式的网络地址，默认为10.96.0.0/12；通常，仅Flannel一类的网络插件需要手动指定该地址；
  • –apiserver-advertise-address：apiserver通告给其他组件的IP地址，一般应该为Master节点的用于集群内部通信的IP地址，0.0.0.0表示节点上所有可用地址；
  • –token-ttl：共享令牌（token）的过期时长，默认为24小时，0表示永不过期；为防止不安全存储等原因导致的令牌泄露危及集群安全，建议为其设定过期时长。未设定该选项时，在token过期后，若期望再向集群中加入其它节点，可以使用如下命令重新创建token，并生成节点加入命令。
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# node ip 192.168.1.119

sudo kubeadm init \
    --apiserver-advertise-address=192.168.1.119 \
    --pod-network-cidr=10.244.0.0/16 \
    --service-cidr=10.245.0.0/16

# output ------------------------

Your Kubernetes control-plane has initialized successfully!

To start using your cluster, you need to run the following as a regular user:

  mkdir -p $HOME/.kube
  sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
  sudo chown $(id -u):$(id -g) $HOME/.kube/config

Alternatively, if you are the root user, you can run:

  export KUBECONFIG=/etc/kubernetes/admin.conf

You should now deploy a pod network to the cluster.
Run "kubectl apply -f [podnetwork].yaml" with one of the options listed at:
  https://kubernetes.io/docs/concepts/cluster-administration/addons/

Then you can join any number of worker nodes by running the following on each as root:

kubeadm join 192.168.1.119:6443 --token vldwrp.5p31pom71n355r2k \
	--discovery-token-ca-cert-hash sha256:b8a5fd92b8506651a6b7a23d9176eeb4c66c8ff92a5d59ea0a5e084d494ae64f 

# -----------------------------------------------------------

mkdir -p $HOME/.kube
sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
sudo chown $(id -u):$(id -g) $HOME/.kube/config
export KUBECONFIG=/etc/kubernetes/admin.conf

# 检查 pods， 发现 coredns 在pending，是因为在等待网络插件的安装
kubectl get pods --all-namespaces
NAMESPACE     NAME                                   READY   STATUS    RESTARTS   AGE
kube-system   coredns-558bd4d5db-76fbb               0/1     Pending   0          64s
kube-system   coredns-558bd4d5db-vpjf4               0/1     Pending   0          64s
kube-system   etcd-ubuntu18-119                      1/1     Running   0          79s
kube-system   kube-apiserver-ubuntu18-119            1/1     Running   0          79s
kube-system   kube-controller-manager-ubuntu18-119   1/1     Running   0          71s
kube-system   kube-proxy-k8xth                       1/1     Running   0          64s
kube-system   kube-scheduler-ubuntu18-119            1/1     Running   0          71s

还有非常重要的一步是 部署网络插件, 插件列表 ， 这里我们选择安装 Flannel

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# 安装网络插件
kubectl apply -f https://raw.githubusercontent.com/coreos/flannel/master/Documentation/kube-flannel.yml

Warning: policy/v1beta1 PodSecurityPolicy is deprecated in v1.21+, unavailable in v1.25+
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 created

安装完成，再检查 pods

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kubectl get pods -n kube-system -l app=flannel
NAME                    READY   STATUS    RESTARTS   AGE
kube-flannel-ds-bj57z   1/1     Running   0          17s

# pods running
kubectl get pods -n kube-system
NAME                                   READY   STATUS    RESTARTS   AGE
coredns-558bd4d5db-76fbb               1/1     Running   0          10h
coredns-558bd4d5db-vpjf4               1/1     Running   0          10h
etcd-ubuntu18-119                      1/1     Running   0          10h
kube-apiserver-ubuntu18-119            1/1     Running   0          10h
kube-controller-manager-ubuntu18-119   1/1     Running   0          10h
kube-flannel-ds-89pc6                  1/1     Running   0          10h
kube-flannel-ds-bj57z                  1/1     Running   0          10h
kube-flannel-ds-pnw6c                  1/1     Running   0          10h
kube-proxy-k8xth                       1/1     Running   0          10h
kube-proxy-n8fj8                       1/1     Running   0          10h
kube-proxy-wlfmr                       1/1     Running   0          10h
kube-scheduler-ubuntu18-119            1/1     Running   0          10h

# 此时还只有一个 node
kubectl get nodes
NAME           STATUS   ROLES                  AGE     VERSION
ubuntu18-119   Ready    control-plane,master   3m29s   v1.21.1

以上终于完成了主要节点的设置，接下来是其余 2 个节点的加入。

node1

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kubeadm join 192.168.1.119:6443 --token vldwrp.5p31pom71n355r2k \
	--discovery-token-ca-cert-hash sha256:b8a5fd92b8506651a6b7a23d9176eeb4c66c8ff92a5d59ea0a5e084d494ae64f 

[preflight] Running pre-flight checks
[preflight] Reading configuration from the cluster...
[preflight] FYI: You can look at this config file with 'kubectl -n kube-system get cm kubeadm-config -o yaml'
[kubelet-start] Writing kubelet configuration to file "/var/lib/kubelet/config.yaml"
[kubelet-start] Writing kubelet environment file with flags to file "/var/lib/kubelet/kubeadm-flags.env"
[kubelet-start] Starting the kubelet
[kubelet-start] Waiting for the kubelet to perform the TLS Bootstrap...

This node has joined the cluster:
* Certificate signing request was sent to apiserver and a response was received.
* The Kubelet was informed of the new secure connection details.

Run 'kubectl get nodes' on the control-plane to see this node join the cluster.

node2

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kubeadm join 192.168.1.119:6443 --token vldwrp.5p31pom71n355r2k \
	--discovery-token-ca-cert-hash sha256:b8a5fd92b8506651a6b7a23d9176eeb4c66c8ff92a5d59ea0a5e084d494ae64f 

[preflight] Running pre-flight checks
[preflight] Reading configuration from the cluster...
[preflight] FYI: You can look at this config file with 'kubectl -n kube-system get cm kubeadm-config -o yaml'
[kubelet-start] Writing kubelet configuration to file "/var/lib/kubelet/config.yaml"
[kubelet-start] Writing kubelet environment file with flags to file "/var/lib/kubelet/kubeadm-flags.env"
[kubelet-start] Starting the kubelet
[kubelet-start] Waiting for the kubelet to perform the TLS Bootstrap...

This node has joined the cluster:
* Certificate signing request was sent to apiserver and a response was received.
* The Kubelet was informed of the new secure connection details.

Run 'kubectl get nodes' on the control-plane to see this node join the cluster.

测试

当 2 个节点成功加入集群后，我们可以在 master 节点检查 nodes 情况, 3 个 nodes 的情况

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kubectl get nodes -o wide

NAME           STATUS   ROLES                  AGE   VERSION   INTERNAL-IP     EXTERNAL-IP   OS-IMAGE             KERNEL-VERSION     CONTAINER-RUNTIME
ubuntu18-119   Ready    control-plane,master   10h   v1.21.1   192.168.1.119   <none>        Ubuntu 18.04.5 LTS   5.4.0-72-generic   docker://20.10.6
ubuntu18-120   Ready    <none>                 10h   v1.21.1   192.168.1.120   <none>        Ubuntu 18.04.5 LTS   5.4.0-42-generic   docker://20.10.6
ubuntu18-121   Ready    <none>                 10h   v1.21.1   192.168.1.121   <none>        Ubuntu 18.04.5 LTS   5.4.0-42-generic   docker://20.10.6

到此为止，一个master，并附带有三个node的kubernetes集群基础设施已经部署完成，用户随后即可测试其核心功能。例如，下面的命令可将demoapp以Pod的形式编排运行于集群之上，并通过在集群外部进行访问

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# 在  master 上运行
kubectl create deployment demoapp --image=ikubernetes/demoapp:v1.0

kubectl scale deployment/demoapp --replicas=6

kubectl create service nodeport demoapp --tcp=80:80

## 而后，使用如下命令了解Service对象demoapp使用的NodePort，以便于在集群外部进行访问：
kubectl get svc -l app=demoapp 
NAME      TYPE       CLUSTER-IP      EXTERNAL-IP   PORT(S)        AGE
demoapp   NodePort   10.245.33.169   <none>        80:31938/TCP   6s

## 检查应用 6 个容器的分布情况, 5 个在 120， 1 个在 121
kubectl get pods -o wide
NAME                       READY   STATUS    RESTARTS   AGE   IP           NODE           NOMINATED NODE   READINESS GATES
demoapp-5f7d8f9847-2s6zd   1/1     Running   0          57s   10.244.2.2   ubuntu18-121   <none>           <none>
demoapp-5f7d8f9847-2wqdv   1/1     Running   0          57s   10.244.1.4   ubuntu18-120   <none>           <none>
demoapp-5f7d8f9847-8p7wd   1/1     Running   0          57s   10.244.1.3   ubuntu18-120   <none>           <none>
demoapp-5f7d8f9847-jrmzj   1/1     Running   0          81s   10.244.1.2   ubuntu18-120   <none>           <none>
demoapp-5f7d8f9847-mjk7x   1/1     Running   0          57s   10.244.1.5   ubuntu18-120   <none>           <none>
demoapp-5f7d8f9847-xch2b   1/1     Running   0          57s   10.244.1.6   ubuntu18-120   <none>           <none>

# 查看 service。一个 Service 由一组 backend Pod 组成。这些 Pod 通过 endpoints 暴露出来
#  注意 Service IP 完全是虚拟的，它从来没有走过网络，如果对它如何工作的原理感到好奇， 可以进一步阅读服务代理的内容
kubectl describe svc demoapp
Name:                     demoapp
Namespace:                default
Labels:                   app=demoapp
Annotations:              <none>
Selector:                 app=demoapp
Type:                     NodePort
IP Family Policy:         SingleStack
IP Families:              IPv4
IP:                       10.245.33.169
IPs:                      10.245.33.169
Port:                     80-80  80/TCP
TargetPort:               80/TCP
NodePort:                 80-80  31938/TCP
Endpoints:                10.244.1.44:80,10.244.1.45:80,10.244.1.46:80 + 3 more...
Session Affinity:         None
External Traffic Policy:  Cluster
Events:                   <none>

## 访问 access service port
# master test
curl http://10.245.33.169 
iKubernetes demoapp v1.0 !! ClientIP: 10.244.0.0, ServerName: demoapp-5f7d8f9847-pps49, ServerIP: 10.244.1.49!

# node1 test
curl http://10.245.33.169 
iKubernetes demoapp v1.0 !! ClientIP: 10.244.0.0, ServerName: demoapp-5f7d8f9847-p7vdc, ServerIP: 10.244.1.48!

# node2 test
curl http://10.245.33.169 
iKubernetes demoapp v1.0 !! ClientIP: 10.244.0.0, ServerName: demoapp-5f7d8f9847-2z5g4, ServerIP: 10.244.1.44!

## 在 master 上面，测试 API 注意 node 端口是 31938
curl http://192.168.1.119:31938
iKubernetes demoapp v1.0 !! ClientIP: 10.244.0.0, ServerName: demoapp-5f7d8f9847-2s6zd, ServerIP: 10.244.2.2!

## 在 node1 上面，测试 API 注意 node 端口是 31938
curl http://192.168.1.120:31938
iKubernetes demoapp v1.0 !! ClientIP: 10.244.1.1, ServerName: demoapp-5f7d8f9847-2wqdv, ServerIP: 10.244.1.4!

## 在 node2 上面，测试 API 注意 node 端口是 31938
curl http://192.168.1.121:31938
iKubernetes demoapp v1.0 !! ClientIP: 10.244.2.0, ServerName: demoapp-5f7d8f9847-xch2b, ServerIP: 10.244.1.6!

demoapp是一个web应用，k8s 内部可以通过 service_ip + port “http://10.245.33.169:80" 访问。 集群外部可以通过 “http://NodeIP:31938" 这个URL访问demoapp上的应用，例如于集群外通过浏览器访问”http://192.168.1.119:31938" 。 当然用 Nginx 做一层代理也是可以的， 或者云上的话，就是 load balancer

注意 Service IP 10.245.33.169 完全是虚拟的，它从来没有走过网络，如果对它如何工作的原理感到好奇， 可以进一步阅读 服务代理 的内容。

service forward

  • service virtual ip： 10.245.33.169 port:80
  • node_ip: 192.168.1.x port:31938

请先看一下这篇文章 理解kubernetes环境的iptables 

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# nat 表里面的转发规则 ，关于 destination 是 虚拟 ip 的有两条规则
iptables -t nat -L KUBE-SERVICES -n | grep 10.245.33.169 

KUBE-MARK-MASQ  tcp  -- !10.244.0.0/16        10.245.33.169   /* default/demoapp:80-80 cluster IP */ tcp dpt:80
KUBE-SVC-EGFVCLHG4JMRSQGG  tcp  --  0.0.0.0/0 10.245.33.169   /* default/demoapp:80-80 cluster IP */ tcp dpt:80

# 6 个 pods ，注意 IP 地址
kubectl get pods -o wide 
NAME                      READY STATUS  RESTARTS   AGE     IP            NODE     NOMINATED NODE  READINESS GATES
demoapp-5f7d8f9847-2z5g4  1/1   Running   0      5d17h   10.244.1.44   ubuntu18-120   <none>       <none>
demoapp-5f7d8f9847-dq6s9  1/1   Running   0      5d17h   10.244.1.47   ubuntu18-120   <none>       <none>
demoapp-5f7d8f9847-p7vdc  1/1   Running   0      5d17h   10.244.1.48   ubuntu18-120   <none>       <none>
demoapp-5f7d8f9847-pps49  1/1   Running   0      5d17h   10.244.1.49   ubuntu18-120   <none>       <none>
demoapp-5f7d8f9847-t6c8k  1/1   Running   0      5d17h   10.244.1.46   ubuntu18-120   <none>       <none>
demoapp-5f7d8f9847-wjqmm  1/1   Running   0      5d17h   10.244.1.45   ubuntu18-120   <none>       <none>

# 每个 pods 都有一条规则， 如果有请求是访问 pods 的
iptables -t nat -L -n  | grep 10.244.1
KUBE-MARK-MASQ  all  --  10.244.1.49   0.0.0.0/0  /* default/demoapp:80-80 */
KUBE-MARK-MASQ  all  --  10.244.1.47   0.0.0.0/0  /* default/demoapp:80-80 */
KUBE-MARK-MASQ  all  --  10.244.1.44   0.0.0.0/0  /* default/demoapp:80-80 */
KUBE-MARK-MASQ  all  --  10.244.1.48   0.0.0.0/0  /* default/demoapp:80-80 */
KUBE-MARK-MASQ  all  --  10.244.1.46   0.0.0.0/0  /* default/demoapp:80-80 */
KUBE-MARK-MASQ  all  --  10.244.1.45   0.0.0.0/0  /* default/demoapp:80-80 */

从上面可以看到， iptable 最终进入到 KUBE-MARK-MASQ chain 链， 而最终会 mark 标记后的请求由 kube-proxy 处理

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Chain KUBE-MARK-MASQ (23 references)
target     prot opt source               destination         
MARK       all  --  0.0.0.0/0            0.0.0.0/0            MARK or 0x4000

iptables proxy

检查是哪一种 proxy mode How to find which mode kube-proxy is running in

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root@ubuntu18-119:~# docker logs  k8s_kube-proxy_kube-proxy-k8xth_kube-system_0c7ede9e-3398-42ed-b30d-3e0af106049d_14 
I0601 06:59:18.494352  1 node.go:172] Successfully retrieved node IP: 192.168.1.119
I0601 06:59:18.494404  1 server_others.go:140] Detected node IP 192.168.1.119
W0601 06:59:18.494436  1 server_others.go:598] Unknown proxy mode "", assuming iptables proxy
I0601 06:59:18.617259  1 server_others.go:206] kube-proxy running in dual-stack mode, IPv4-primary
I0601 06:59:18.617285  1 server_others.go:212] Using iptables Proxier.
I0601 06:59:18.617295  1 server_others.go:219] creating dualStackProxier for iptables.
W0601 06:59:18.617306  1 server_others.go:512] detect-local-mode set to ClusterCIDR, but no IPv6 cluster CIDR defined, , defaulting to no-op detect-local for IPv6
I0601 06:59:18.620918  1 server.go:643] Version: v1.21.1
I0601 06:59:18.623937  1 conntrack.go:100] Set sysctl 'net/netfilter/nf_conntrack_max' to 131072
I0601 06:59:18.623965  1 conntrack.go:52] Setting nf_conntrack_max to 131072
I0601 06:59:18.624646  1 conntrack.go:83] Setting conntrack hashsize to 32768
I0601 06:59:18.641659  1 conntrack.go:100] Set sysctl 'net/netfilter/nf_conntrack_tcp_timeout_established' to 86400
I0601 06:59:18.641709  1 conntrack.go:100] Set sysctl 'net/netfilter/nf_conntrack_tcp_timeout_close_wait' to 3600
I0601 06:59:18.647124  1 config.go:315] Starting service config controller
I0601 06:59:18.648113  1 shared_informer.go:240] Waiting for caches to sync for service config
I0601 06:59:18.648459  1 config.go:224] Starting endpoint slice config controller

有两幅图很生动，第一幅是从宏观上，第二幅是从微观上 iptable chain 过程

看完第二幅图，以我们自己的实验环境举例子，结果如下

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# 根据 SVC demoapp get KUBE-SVC-EGFVCLHG4JMRSQGG 
KUBE-SVC-EGFVCLHG4JMRSQGG  tcp  --  0.0.0.0/0    10.245.33.169    /* default/demoapp:80-80 cluster IP */ tcp dpt:80

# check KUBE-SVC-EGFVCLHG4JMRSQGG , probability 就是 load balancer
iptables -t nat -L KUBE-SVC-EGFVCLHG4JMRSQGG -n
Chain KUBE-SVC-EGFVCLHG4JMRSQGG (2 references)
target     prot opt source               destination         
KUBE-SEP-LFNE4UIW5JTX3DLE  all  --  0.0.0.0/0    0.0.0.0/0  /* default/demoapp:80-80 */ statistic mode random probability 0.16666666651
KUBE-SEP-VKI6CD7L7QDWV7PR  all  --  0.0.0.0/0    0.0.0.0/0  /* default/demoapp:80-80 */ statistic mode random probability 0.20000000019
KUBE-SEP-ONGVKLAWWHRT2JYZ  all  --  0.0.0.0/0    0.0.0.0/0  /* default/demoapp:80-80 */ statistic mode random probability 0.25000000000
KUBE-SEP-BWUFDZ7V66HHLROZ  all  --  0.0.0.0/0    0.0.0.0/0  /* default/demoapp:80-80 */ statistic mode random probability 0.33333333349
KUBE-SEP-NQEYALZIWTXZ4WPY  all  --  0.0.0.0/0    0.0.0.0/0  /* default/demoapp:80-80 */ statistic mode random probability 0.50000000000
KUBE-SEP-36MBDHMST2HAATHB  all  --  0.0.0.0/0    0.0.0.0/0  /* default/demoapp:80-80 */

# KUBE-SEP-36MBDHMST2HAATHB
iptables -t nat -L KUBE-SEP-36MBDHMST2HAATHB  -n
Chain KUBE-SEP-36MBDHMST2HAATHB (1 references)
target     prot opt source               destination         
KUBE-MARK-MASQ  all  --  10.244.1.49     0.0.0.0/0     /* default/demoapp:80-80 */
DNAT       tcp  --  0.0.0.0/0            0.0.0.0/0     /* default/demoapp:80-80 */ tcp DNAT [unsupported revision]

部署 dashboard

官网： https://kubernetes.io/zh/docs/tasks/access-application-cluster/web-ui-dashboard/
github： https://github.com/kubernetes/dashboard
Dashboard 是基于网页的 Kubernetes 用户界面。 你可以使用 Dashboard 将容器应用部署到 Kubernetes 集群中，也可以对容器应用排错，还能管理集群资源。 你可以使用 Dashboard 获取运行在集群中的应用的概览信息，也可以创建或者修改 Kubernetes 资源 （如 Deployment，Job，DaemonSet 等等）。 例如，你可以对 Deployment 实现弹性伸缩、发起滚动升级、重启 Pod 或者使用向导创建新的应用。

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# To deploy Dashboard, execute following command:
kubectl apply -f https://raw.githubusercontent.com/kubernetes/dashboard/v2.2.0/aio/deploy/recommended.yaml

namespace/kubernetes-dashboard created
serviceaccount/kubernetes-dashboard created
service/kubernetes-dashboard created
secret/kubernetes-dashboard-certs created
secret/kubernetes-dashboard-csrf created
secret/kubernetes-dashboard-key-holder created
configmap/kubernetes-dashboard-settings created
role.rbac.authorization.k8s.io/kubernetes-dashboard created
clusterrole.rbac.authorization.k8s.io/kubernetes-dashboard created
rolebinding.rbac.authorization.k8s.io/kubernetes-dashboard created
clusterrolebinding.rbac.authorization.k8s.io/kubernetes-dashboard created
deployment.apps/kubernetes-dashboard created
service/dashboard-metrics-scraper created
deployment.apps/dashboard-metrics-scraper created

# Creating a Service Account
cat <<EOF | kubectl apply -f -
apiVersion: v1
kind: ServiceAccount
metadata:
  name: admin-user
  namespace: kubernetes-dashboard
EOF

# Creating a ClusterRoleBinding
cat <<EOF | kubectl apply -f -
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
  name: admin-user
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: cluster-admin
subjects:
- kind: ServiceAccount
  name: admin-user
  namespace: kubernetes-dashboard
EOF

# Getting a Bearer Token
kubectl -n kubernetes-dashboard get secret $(kubectl -n kubernetes-dashboard get sa/admin-user -o jsonpath="{.secrets[0].name}") -o go-template="{{.data.token | base64decode}}"

# token 应该是很长的一串字符，类似
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

命令行代理

还得使用代理才能访问到 Dashboard 的服务

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kubectl proxy 
Starting to serve on 127.0.0.1:8001

kubectl 会使得 Dashboard 可以通过 http://localhost:8001/api/v1/namespaces/kubernetes-dashboard/services/https:kubernetes-dashboard:/proxy/ 访问

打开 master 虚拟机桌面，用 Firefox 浏览器输入网址 http://localhost:8001/api/v1/namespaces/kubernetes-dashboard/services/https:kubernetes-dashboard:/proxy/ 并输入上面得到的 Bearer Token 登录

成功登录以后，就可以看到整个集群的情况和做一些相关的操作了

踩过的坑

虚拟机双网卡

如果虚拟机是双网卡，一般默认的是 NAT 那一张，桥接的在第二张。在我本次实验中，当安装完 flannel 网络后，却发现有错误。

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# 如果部署出现问题可通过如下命令查看日志
kubectl logs kube-flannel-ds-6xxs5 --namespace=kube-system
kubectl describe pod kube-flannel-ds-6xxs5 --namespace=kube-system

日志的结果显示，用了 NAT 那一张网卡，导致和最开始设置的 apiserver-advertise-address=192.168.1.119 无法连接，启动失败了。
临时修复的办法就是，禁用 NAT 网卡，永久修复的办法就是关机后，移除 NAT 网卡(网络适配器)

Flannel网络

通常，仅Flannel一类的网络插件需要手动指定该地址

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--service-cidr=10.245.0.0/16