kubeadm是Kubernetes官方提供的快速安装和初始化Kubernetes集群的工具,目前的还处于孵化开发状态,伴随Kubernetes每个版本的发布都会同步更新。 当然,目前的kubeadm是不能用于生产环境的。 但伴随着Kubernetes每次版本升级,kubeadm都会对集群配置方面的一些实践做调整,通过实验kubeadm我们可以学习到Kubernetes官方在集群配置上一些新的最佳实践。

Kubernetes 1.8已经发布,为了跟上官方更新的脚步,接下来体验一下Kubernetes 1.8中的kubeadm。

1.准备

1.1系统配置

在安装之前,需要先做如下准备。两台CentOS 7.3主机如下:

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cat /etc/hosts
192.168.61.11 node1
192.168.61.12 node2

如果各个主机启用了防火墙,需要开放Kubernetes各个组件所需要的端口,可以查看Installing kubeadm中的”Check required ports”一节。 这里简单起见在各节点禁用防火墙:

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systemctl stop firewalld
systemctl disable firewalld

创建/etc/sysctl.d/k8s.conf文件,添加如下内容:

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net.bridge.bridge-nf-call-ip6tables = 1
net.bridge.bridge-nf-call-iptables = 1

执行sysctl -p /etc/sysctl.d/k8s.conf使修改生效。

禁用SELINUX:

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setenforce 0
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vi /etc/selinux/config
SELINUX=disabled

Kubernetes 1.8开始要求关闭系统的Swap,如果不关闭,默认配置下kubelet将无法启动。可以通过kubelet的启动参数--fail-swap-on=false更改这个限制。 我们这里关闭系统的Swap:

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swapoff -a

修改 /etc/fstab 文件,注释掉 SWAP 的自动挂载,使用free -m确认swap已经关闭。

swappiness参数调整,修改/etc/sysctl.d/k8s.conf添加下面一行:

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vm.swappiness=0

执行sysctl -p /etc/sysctl.d/k8s.conf使修改生效。

1.2安装Docker

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yum install -y yum-utils device-mapper-persistent-data lvm2
yum-config-manager \
    --add-repo \
    https://download.docker.com/linux/centos/docker-ce.repo

查看当前的Docker版本:

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yum list docker-ce.x86_64  --showduplicates |sort -r
docker-ce.x86_64            17.09.0.ce-1.el7.centos             docker-ce-stable
docker-ce.x86_64            17.06.2.ce-1.el7.centos             docker-ce-stable
docker-ce.x86_64            17.06.1.ce-1.el7.centos             docker-ce-stable
docker-ce.x86_64            17.06.0.ce-1.el7.centos             docker-ce-stable
docker-ce.x86_64            17.03.2.ce-1.el7.centos             docker-ce-stable
docker-ce.x86_64            17.03.1.ce-1.el7.centos             docker-ce-stable
docker-ce.x86_64            17.03.0.ce-1.el7.centos             docker-ce-stable

Kubernetes 1.8已经针对Docker的1.11.2, 1.12.6, 1.13.1和17.03.2等版本做了验证。 因为我们这里在各节点安装docker的17.03.2版本。

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yum makecache fast

yum install -y --setopt=obsoletes=0 \
  docker-ce-17.03.2.ce-1.el7.centos \
  docker-ce-selinux-17.03.2.ce-1.el7.centos

systemctl start docker
systemctl enable docker

Docker从1.13版本开始调整了默认的防火墙规则,禁用了iptables filter表中FOWARD链,这样会引起Kubernetes集群中跨Node的Pod无法通信,在各个Docker节点执行下面的命令:

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iptables -P FORWARD ACCEPT

可在docker的systemd unit文件中以ExecStartPost加入上面的命令:

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ExecStartPost=/usr/sbin/iptables -P FORWARD ACCEPT
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systemctl daemon-reload
systemctl restart docker

2.安装kubeadm和kubelet

下面在各节点安装kubeadm和kubelet:

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cat <<EOF > /etc/yum.repos.d/kubernetes.repo
[kubernetes]
name=Kubernetes
baseurl=https://packages.cloud.google.com/yum/repos/kubernetes-el7-x86_64
enabled=1
gpgcheck=1
repo_gpgcheck=1
gpgkey=https://packages.cloud.google.com/yum/doc/yum-key.gpg
        https://packages.cloud.google.com/yum/doc/rpm-package-key.gpg
EOF

测试地址https://packages.cloud.google.com/yum/repos/kubernetes-el7-x86_64是否可用,如果不可用需要科学上网。

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curl https://packages.cloud.google.com/yum/repos/kubernetes-el7-x86_64
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yum makecache fast
yum install -y kubelet kubeadm kubectl

... 
Installed:
  kubeadm.x86_64 0:1.8.0-0     kubectl.x86_64 0:1.8.0-0    kubelet.x86_64 0:1.8.0-0

Dependency Installed:
  kubernetes-cni.x86_64 0:0.5.1-0             socat.x86_64 0:1.7.3.2-2.el7
  • 从安装结果可以看出还安装了kubernetes-cni和socat两个依赖:

Kubernetes文档中kubelet的启动参数

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  --cgroup-driver string Driver that the kubelet uses to manipulate cgroups on the host.
		Possible values: 'cgroupfs', 'systemd' (default "cgroupfs")

默认值为cgroupfs,但是我们注意到yum安装kubelet,kubeadm时生成10-kubeadm.conf文件中将这个参数值改成了systemd。

查看kubelet的 /etc/systemd/system/kubelet.service.d/10-kubeadm.conf文件,其中包含如下内容:

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Environment="KUBELET_CGROUP_ARGS=--cgroup-driver=systemd"

使用docker info打印docker信息:

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docker info
......
Server Version: 17.03.2-ce
......
Cgroup Driver: cgroupfs

可以看出docker 17.03使用的Cgroup Driver为cgroupfs。

于是修改各节点docker的cgroup driver使其和kubelet一致,即修改或创建/etc/docker/daemon.json,加入下面的内容:

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{
  "exec-opts": ["native.cgroupdriver=systemd"]
}

重启docker:

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systemctl restart docker
systemctl status docker

在各节点开机启动kubelet服务:

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systemctl enable kubelet.service

3.使用kubeadm init初始化集群

接下来使用kubeadm初始化集群,选择node1作为Master Node,在node1上执行下面的命令:

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kubeadm init \
  --kubernetes-version=v1.8.0 \
  --pod-network-cidr=10.244.0.0/16 \
  --apiserver-advertise-address=192.168.61.11

因为我们选择flannel作为Pod网络插件,所以上面的命令指定–pod-network-cidr=10.244.0.0/16。

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kubeadm init \
>   --kubernetes-version=v1.8.0 \
>   --pod-network-cidr=10.244.0.0/16 \
>   --apiserver-advertise-address=192.168.61.11
[kubeadm] WARNING: kubeadm is in beta, please do not use it for production clusters.
[init] Using Kubernetes version: v1.8.0
[init] Using Authorization modes: [Node RBAC]
[preflight] Running pre-flight checks
[preflight] WARNING: firewalld is active, please ensure ports [6443 10250] are open or your cluster may not function correctly
[preflight] Starting the kubelet service
[kubeadm] WARNING: starting in 1.8, tokens expire after 24 hours by default (if you require a non-expiring token use --token-ttl 0)
[certificates] Generated ca certificate and key.
[certificates] Generated apiserver certificate and key.
[certificates] apiserver serving cert is signed for DNS names [node1 kubernetes kubernetes.default kubernetes.default.svc kubernetes.default.svc.cluster.local] and IPs [10.96.0.1 192.168.61.11]
[certificates] Generated apiserver-kubelet-client certificate and key.
[certificates] Generated sa key and public key.
[certificates] Generated front-proxy-ca certificate and key.
[certificates] Generated front-proxy-client certificate and key.
[certificates] Valid certificates and keys now exist in "/etc/kubernetes/pki"
[kubeconfig] Wrote KubeConfig file to disk: "admin.conf"
[kubeconfig] Wrote KubeConfig file to disk: "kubelet.conf"
[kubeconfig] Wrote KubeConfig file to disk: "controller-manager.conf"
[kubeconfig] Wrote KubeConfig file to disk: "scheduler.conf"
[controlplane] Wrote Static Pod manifest for component kube-apiserver to "/etc/kubernetes/manifests/kube-apiserver.yaml"
[controlplane] Wrote Static Pod manifest for component kube-controller-manager to "/etc/kubernetes/manifests/kube-controller-manager.yaml"
[controlplane] Wrote Static Pod manifest for component kube-scheduler to "/etc/kubernetes/manifests/kube-scheduler.yaml"
[etcd] Wrote Static Pod manifest for a local etcd instance to "/etc/kubernetes/manifests/etcd.yaml"
[init] Waiting for the kubelet to boot up the control plane as Static Pods from directory "/etc/kubernetes/manifests"
[init] This often takes around a minute; or longer if the control plane images have to be pulled.
[apiclient] All control plane components are healthy after 28.505733 seconds
[uploadconfig] Storing the configuration used in ConfigMap "kubeadm-config" in the "kube-system" Namespace
[markmaster] Will mark node node1 as master by adding a label and a taint
[markmaster] Master node1 tainted and labelled with key/value: node-role.kubernetes.io/master=""
[bootstraptoken] Using token: 9e68dd.7117f03c900f9234
[bootstraptoken] Configured RBAC rules to allow Node Bootstrap tokens to post CSRs in order for nodes to get long term certificate credentials
[bootstraptoken] Configured RBAC rules to allow the csrapprover controller automatically approve CSRs from a Node Bootstrap Token
[bootstraptoken] Creating the "cluster-info" ConfigMap in the "kube-public" namespace
[addons] Applied essential addon: kube-dns
[addons] Applied essential addon: kube-proxy

Your Kubernetes master has initialized successfully!

To start using your cluster, you need to run (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

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

You can now join any number of machines by running the following on each node
as root:

  kubeadm join --token 9e68dd.7117f03c900f9234 192.168.61.11:6443 --discovery-token-ca-cert-hash sha256:82a08ef9c830f240e588a26a8ff0a311e6fe3127c1ee4c5fc019f1369007c0b7

上面记录了完成的初始化输出的内容。

其中由以下关键内容: * kubeadm 1.8当前还处于beta状态,还不能用于生产环境。目前来看这东西安装的etcd和apiserver都是单节点,当然不能用于生产环境。 * RBAC模式已经在Kubernetes 1.8中稳定可用。kubeadm 1.8也默认启用了RBAC * 接下来是生成证书和相关的kubeconfig文件,这个目前我们在Kubernetes 1.6 高可用集群部署也是这么做的,目前没看出有什么新东西 * 生成token记录下来,后边使用kubeadm join往集群中添加节点时会用到 * 另外注意kubeadm还报了starting in 1.8, tokens expire after 24 hours by default (if you require a non-expiring token use --token-ttl 0)的警告 * 下面的命令是配置常规用户如何使用kubectl访问集群: mkdir -p $HOME/.kube sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config sudo chown $(id -u):$(id -g) $HOME/.kube/config * 最后给出了将节点加入集群的命令kubeadm join --token 9e68dd.7117f03c900f9234 192.168.61.11:6443 --discovery-token-ca-cert-hash sha256:82a08ef9c830f240e588a26a8ff0a311e6fe3127c1ee4c5fc019f1369007c0b7

查看一下集群状态:

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kubectl get cs
NAME                 STATUS    MESSAGE              ERROR
scheduler            Healthy   ok
controller-manager   Healthy   ok
etcd-0               Healthy   {"health": "true"}

确认个组件都处于healthy状态。

集群初始化如果遇到问题,可以使用下面的命令进行清理:

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kubeadm reset
ifconfig cni0 down
ip link delete cni0
ifconfig flannel.1 down
ip link delete flannel.1
rm -rf /var/lib/cni/

4.安装Pod Network

接下来安装flannel network add-on:

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mkdir -p ~/k8s/
wget https://raw.githubusercontent.com/coreos/flannel/master/Documentation/kube-flannel.yml
kubectl apply -f  kube-flannel.yml
clusterrole "flannel" created
clusterrolebinding "flannel" created
serviceaccount "flannel" created
configmap "kube-flannel-cfg" created
daemonset "kube-flannel-ds" created

这里注意kube-flannel.yml这个文件中已经包含了ServiceAccount, ClusterRole和ClusterRoleBinding,原来是在一个单独的kube-flannel-rbac.yml文件中。kube-flannel.yml这个文件里的flannel的镜像是0.9.0,quay.io/coreos/flannel:v0.9.0-amd64

如果Node有多个网卡的话,参考flannel issues 39701,目前需要在kube-flannel.yml中使用--iface参数指定集群主机内网网卡的名称,否则可能会出现dns无法解析。需要将kube-flannel.yml下载到本地,flanneld启动参数加上--iface=<iface-name>

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......
apiVersion: extensions/v1beta1
kind: DaemonSet
metadata:
  name: kube-flannel-ds
......
containers:
      - name: kube-flannel
        image: quay.io/coreos/flannel:v0.9.0-amd64
        command: [ "/opt/bin/flanneld", "--ip-masq", "--kube-subnet-mgr", "--iface=eth1" ]
......

使用kubectl get pod --all-namespaces -o wide确保所有的Pod都处于Running状态。

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kubectl get pod --all-namespaces -o wide

5.master node参与工作负载

使用kubeadm初始化的集群,出于安全考虑Pod不会被调度到Master Node上,也就是说Master Node不参与工作负载。

这里搭建的是测试环境可以使用下面的命令使Master Node参与工作负载:

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kubectl taint nodes node1 node-role.kubernetes.io/master-
node "node1" untainted

6.测试DNS

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kubectl run curl --image=radial/busyboxplus:curl -i --tty
If you don't see a command prompt, try pressing enter.
[ root@curl-2716574283-xr8zd:/ ]$

进入后执行nslookup kubernetes.default确认解析正常:

``` nslookup kubernetes.default Server: 10.96.0.10 Address 1: 10.96.0.10 kube-dns.kube-system.svc.cluster.local

Name: kubernetes.default Address 1: 10.96.0.1 kubernetes.default.svc.cluster.local

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## 7.向Kubernetes集群添加Node

下面我们将node2这个主机添加到Kubernetes集群中,在node2上执行:

kubeadm join –token 9e68dd.7117f03c900f9234 192.168.61.11:6443 –discovery-token-ca-cert-hash sha256:82a08ef9c830f240e588a26a8ff0a311e6fe3127c1ee4c5fc019f1369007c0b7 [kubeadm] WARNING: kubeadm is in beta, please do not use it for production clusters. [preflight] Running pre-flight checks [discovery] Trying to connect to API Server “192.168.61.11:6443” [discovery] Created cluster-info discovery client, requesting info from “https://192.168.61.11:6443" [discovery] Requesting info from “https://192.168.61.11:6443" again to validate TLS against the pinned public key [discovery] Cluster info signature and contents are valid and TLS certificate validates against pinned roots, will use API Server “192.168.61.11:6443” [discovery] Successfully established connection with API Server “192.168.61.11:6443” [bootstrap] Detected server version: v1.8.0 [bootstrap] The server supports the Certificates API (certificates.k8s.io/v1beta1)

Node join complete: * Certificate signing request sent to master and response received. * Kubelet informed of new secure connection details.

Run ‘kubectl get nodes’ on the master to see this machine join.

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这次很是顺利,下面在master节点上执行命令查看集群中的节点:

kubectl get nodes NAME STATUS ROLES AGE VERSION node1 Ready master 25m v1.8.0 node2 Ready 10m v1.8.0

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### 如何从集群中移除Node

如果需要从集群中移除node2这个Node执行下面的命令:

在master节点上执行:

kubectl drain node2 –delete-local-data –force –ignore-daemonsets kubectl delete node node2

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在node2上执行:

kubeadm reset ifconfig cni0 down ip link delete cni0 ifconfig flannel.1 down ip link delete flannel.1 rm -rf /var/lib/cni/

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## 8.dashboard插件部署

注意当前dashboard的版本已经是1.7.1了。
而1.7.x版本的dashboard对安全做了增强,默认需要以https的方式访问,增加了登录的页面,同时增加了一个`gcr.io/google_containers/kubernetes-dashboard-init-amd64`的init容器。

另外需要注意dashboard调整了部署文件的源码目录结构:

mkdir -p ~/k8s/ wget https://raw.githubusercontent.com/kubernetes/dashboard/master/src/deploy/recommended/kubernetes-dashboard.yaml kubectl create -f kubernetes-dashboard.yaml

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kubernetes-dashboard.yaml文件中的ServiceAccount `kubernetes-dashboard`只有相对较小的权限,因此我们创建一个`kubernetes-dashboard-admin`的ServiceAccount并授予集群admin的权限,创建kubernetes-dashboard-admin.rbac.yaml:

apiVersion: v1 kind: ServiceAccount metadata: labels: k8s-app: kubernetes-dashboard name: kubernetes-dashboard-admin namespace: kube-system


apiVersion: rbac.authorization.k8s.io/v1beta1 kind: ClusterRoleBinding metadata: name: kubernetes-dashboard-admin labels: k8s-app: kubernetes-dashboard roleRef: apiGroup: rbac.authorization.k8s.io kind: ClusterRole name: cluster-admin subjects: - kind: ServiceAccount name: kubernetes-dashboard-admin namespace: kube-system

kubectl create -f kubernetes-dashboard-admin.rbac.yaml serviceaccount “kubernetes-dashboard-admin” created clusterrolebinding “kubernetes-dashboard-admin” created

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查看kubernete-dashboard-admin的token:

kubectl -n kube-system get secret | grep kubernetes-dashboard-admin kubernetes-dashboard-admin-token-pfss5 kubernetes.io/service-account-token 3 14s

kubectl describe -n kube-system secret/kubernetes-dashboard-admin-token-pfss5 Name: kubernetes-dashboard-admin-token-pfss5 Namespace: kube-system Labels: Annotations: kubernetes.io/service-account.name=kubernetes-dashboard-admin kubernetes.io/service-account.uid=1029250a-ad76-11e7-9a1d-08002778b8a1

Type: kubernetes.io/service-account-token

Data

ca.crt: 1025 bytes namespace: 11 bytes token: eyJhbGciOiJSUzI1NiIsInR5cCI6IkpXVCJ9.eyJpc3MiOiJrdWJlcm5ldGVzL3NlcnZpY2VhY2NvdW50Iiwia3ViZXJuZXRlcy5pby9zZXJ2aWNlYWNjb3VudC9uYW1lc3BhY2UiOiJrdWJlLXN5c3RlbSIsImt1YmVybmV0ZXMuaW8vc2VydmljZWFjY291bnQvc2VjcmV0Lm5hbWUiOiJrdWJlcm5ldGVzLWRhc2hib2FyZC1hZG1pbi10b2tlbi1wZnNzNSIsImt1YmVybmV0ZXMuaW8vc2VydmljZWFjY291bnQvc2VydmljZS1hY2NvdW50Lm5hbWUiOiJrdWJlcm5ldGVzLWRhc2hib2FyZC1hZG1pbiIsImt1YmVybmV0ZXMuaW8vc2VydmljZWFjY291bnQvc2VydmljZS1hY2NvdW50LnVpZCI6IjEwMjkyNTBhLWFkNzYtMTFlNy05YTFkLTA4MDAyNzc4YjhhMSIsInN1YiI6InN5c3RlbTpzZXJ2aWNlYWNjb3VudDprdWJlLXN5c3RlbTprdWJlcm5ldGVzLWRhc2hib2FyZC1hZG1pbiJ9.Bs6h65aFCFkEKBO_h4muoIK3XdTcfik-pNM351VogBJD_pk5grM1PEWdsCXpR45r8zUOTpGM-h8kDwgOXwy2i8a5RjbUTzD3OQbPJXqa1wBk0ABkmqTuw-3PWMRg_Du8zuFEPdKDFQyWxiYhUi_v638G-R5RdZD_xeJAXmKyPkB3VsqWVegoIVTaNboYkw6cgvMa-4b7IjoN9T1fFlWCTZI8BFXbM8ICOoYMsOIJr3tVFf7d6oVNGYqaCk42QL_2TfB6xMKLYER9XDh753-_FDVE5ENtY5YagD3T_s44o0Ewara4P9C3hYRKdJNLxv7qDbwPl3bVFH3HXbsSxxF3TQ

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在dashboard的登录窗口使用上面的token登录。



## 9.heapster插件部署

下面安装Heapster为集群添加使用统计和监控功能,为Dashboard添加仪表盘。 使用InfluxDB做为Heapster的后端存储,开始部署:

mkdir -p ~/k8s/heapster cd ~/k8s/heapster wget https://raw.githubusercontent.com/kubernetes/heapster/master/deploy/kube-config/influxdb/grafana.yaml wget https://raw.githubusercontent.com/kubernetes/heapster/master/deploy/kube-config/rbac/heapster-rbac.yaml wget https://raw.githubusercontent.com/kubernetes/heapster/master/deploy/kube-config/influxdb/heapster.yaml wget https://raw.githubusercontent.com/kubernetes/heapster/master/deploy/kube-config/influxdb/influxdb.yaml

kubectl create -f ./

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最后确认所有的pod都处于running状态,打开Dashboard,集群的使用统计会以仪表盘的形式显示出来。

本次安装涉及到的Docker镜像:

gcr.io/google_containers/kube-apiserver-amd64:v1.8.0 gcr.io/google_containers/kube-controller-manager-amd64:v1.8.0 gcr.io/google_containers/kube-scheduler-amd64:v1.8.0 gcr.io/google_containers/kube-proxy-amd64:v1.8.0 gcr.io/google_containers/k8s-dns-sidecar-amd64:1.14.5 gcr.io/google_containers/k8s-dns-kube-dns-amd64:1.14.5 gcr.io/google_containers/k8s-dns-dnsmasq-nanny-amd64:1.14.5 quay.io/coreos/flannel:v0.9.0-amd64 gcr.io/google_containers/etcd-amd64:3.0.17 gcr.io/google_containers/pause-amd64:3.0 quay.io/coreos/flannel:v0.9.0-amd64

gcr.io/google_containers/kubernetes-dashboard-amd64:v1.7.1 gcr.io/google_containers/kubernetes-dashboard-init-amd64:v1.0.0 gcr.io/google_containers/heapster-influxdb-amd64:v1.3.3 gcr.io/google_containers/heapster-grafana-amd64:v4.4.3 gcr.io/google_containers/heapster-amd64:v1.4.0 ```

参考