使用kubeadm安装Kubernetes 1.8版本

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本，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：

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：

systemctl stop firewalld
systemctl disable firewalld

创建/etc/sysctl.d/k8s.conf文件，添加如下内容：

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：

setenforce 0

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:

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：

vm.swappiness=0

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

1.2安装Docker

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：

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。

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：

iptables -P FORWARD ACCEPT

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

ExecStartPost=/usr/sbin/iptables -P FORWARD ACCEPT

systemctl daemon-reload
systemctl restart docker

2.安装kubeadm和kubelet

下面在各节点安装kubeadm和kubelet：

cat    --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：

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：

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：

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=

......
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。

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：

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

6.测试DNS

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

7.向Kubernetes集群添加Node

下面我们将k8s-node2这个主机添加到Kubernetes集群中，在k8s-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.

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

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

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/

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

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

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.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.Bs6h65aFCFkEKBO_h4muoIK3XdTcfik-pNM351VogBJD_pk5grM1PEWdsCXpR45r8zUOTpGM-h8kDwgOXwy2i8a5RjbUTzD3OQbPJXqa1wBk0ABkmqTuw-3PWMRg_Du8zuFEPdKDFQyWxiYhUi_v638G-R5RdZD_xeJAXmKyPkB3VsqWVegoIVTaNboYkw6cgvMa-4b7IjoN9T1fFlWCTZI8BFXbM8ICOoYMsOIJr3tVFf7d6oVNGYqaCk42QL_2TfB6xMKLYER9XDh753-_FDVE5ENtY5YagD3T_s44o0Ewara4P9C3hYRKdJNLxv7qDbwPl3bVFH3HXbsSxxF3TQ

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 ./

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

• 来源：青蛙小白博客
• Installing kubeadm
• Using kubeadm to Create a Cluster
• Get Docker CE for CentOS
• Kubernetes Dashboard Access-control