kubernetes之Kubeadm快速安装v1.12.0版

通过Kubeadm只需几条命令即起一个单机版kubernetes集群系统，而后快速上手k8s。
在kubeadm中，需手动安装Docker和kubeket服务，Docker运行容器引擎，kubelet是启动Pod的核心组件，每一个节点都安装好kubelet和Docker，那么运行容器和Pod的环境就准备好了，在此基础之上，使用Kubeadm工具自动配置kubelet并启动kubelet服务，将Master所有组件和Node上剩余的kube-proxy组件都运行为Pod，托管在k8s之上。

服务器规划

三台机器：一台master、两个Node：

• k8s-master：10.3.1.20
• k8s-node01：10.3.1.21
• k8s-node02：10.3.1.25
• OS：Ubuntu16.04
• Docker：17.03.2-ce

安装前准备

1、master节点到各Node节点SSH免密登录。
2、时间同步。
3、各Node必须关闭swap：swapoff -a，否则kubelet启动失败。
4、各节点主机名和IP加入/etc/hosts解析

安装Docker

所有k8s节点安装Docker Daemon：

apt-get update
apt-get install \
    apt-transport-https \
    ca-certificates \
    curl \
    software-properties-common
curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -
apt-key fingerprint 0EBFCD88
add-apt-repository \
    "deb [arch=amd64] https://download.docker.com/linux/ubuntu \
    $(lsb_release -cs) \
    stable"
apt-get update
apt-get install -y docker-ce=17.03.2~ce-0~ubuntu-xenial

安装完Docker后，设置FORWARD规则为ACCEPT

#默认为DROP
 iptables -P FORWARD ACCEPT

安装kubeadm工具

• 所有节点都需要安装kubeadm

apt-get update && apt-get install -y apt-transport-https curl
curl -s https://packages.cloud.google.com/apt/doc/apt-key.gpg | apt-key add -
echo 'deb http://apt.kubernetes.io/ kubernetes-xenial main' >/etc/apt/sources.list.d/kubernetes.list
apt-get update
apt-get install -y  kubeadm

#它会自动安装kubeadm、kubectl、kubelet、kubernetes-cni、socat

安装完后，设置kubelet服务开机自启：

systemctl enable kubelet

必须设置Kubelet开机自启动，才能让k8s集群各组件在系统重启后自动运行。

部署集群

有了上面这些基础设置后，就可以开始用kubeadm init部署k8s集群了。

在k8s-master上操作

这一步之前确保swap已关闭。

kubeadm init -h可查看帮助信息：

root@k8s-master:~# kubeadm  init -h
 ##查看init可用的参数，这里使用这两个参数：
   --pod-network-cidr string ： 自定义Pod网络
   --ignore-preflight-errors strings： 忽略一些错误

开始初始化集群

root@k8s-master:~# kubeadm init  --pod-network-cidr 192.168.0.0/16 --ignore-preflight-errors=all

输出如下信息：

#初始化kubernetes，Kubeadm默认安装当前最新版本kubernetes
[init] using Kubernetes version: v1.12.0
#安装之前检测当前是否符合k8s运行环境，因为忽略了所有错误所以这里很快就通过了。
[preflight] running pre-flight checks
[preflight/images] Pulling images required for setting up a Kubernetes cluster
[preflight/images] This might take a minute or two, depending on the speed of your internet connection
[preflight/images] You can also perform this action in beforehand using 'kubeadm config images pull'
#写入kubelet相关配置文件，并启动kubelet服务
[kubelet] Writing kubelet environment file with flags to file "/var/lib/kubelet/kubeadm-flags.env"
[kubelet] Writing kubelet configuration to file "/var/lib/kubelet/config.yaml"
[preflight] Activating the kubelet service
#自动生成集群用到的证书
[certificates] Generated front-proxy-ca certificate and key.
[certificates] Generated front-proxy-client certificate and key.
[certificates] Generated etcd/ca certificate and key.
[certificates] Generated etcd/server certificate and key.
[certificates] etcd/server serving cert is signed for DNS names [k8s-master localhost] and IPs [127.0.0.1 ::1]
[certificates] Generated apiserver-etcd-client certificate and key.
[certificates] Generated etcd/peer certificate and key.
[certificates] etcd/peer serving cert is signed for DNS names [k8s-master localhost] and IPs [10.3.1.20 127.0.0.1 ::1]
[certificates] Generated etcd/healthcheck-client certificate and key.
[certificates] Generated ca certificate and key.
[certificates] Generated apiserver-kubelet-client certificate and key.
[certificates] Generated apiserver certificate and key.
[certificates] apiserver serving cert is signed for DNS names [k8s-master kubernetes kubernetes.default kubernetes.default.svc kubernetes.default.svc.cluster.local] and IPs [10.96.0.1 10.3.1.20]
[certificates] valid certificates and keys now exist in "/etc/kubernetes/pki"
[certificates] Generated sa key and public key.
#生成kubelet配置信息写入相应的文件
[kubeconfig] Wrote KubeConfig file to disk: "/etc/kubernetes/admin.conf"
[kubeconfig] Wrote KubeConfig file to disk: "/etc/kubernetes/kubelet.conf"
[kubeconfig] Wrote KubeConfig file to disk: "/etc/kubernetes/controller-manager.conf"
[kubeconfig] Wrote KubeConfig file to disk: "/etc/kubernetes/scheduler.conf"
#生成pod清单文件，kubelet将根据此清单文件创建各组件的Pod
[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"
#根据清单目录开始启动Pod
[init] waiting for the kubelet to boot up the control plane as Static Pods from directory "/etc/kubernetes/manifests"
[init] this might take a minute or longer if the control plane images have to be pulled
[apiclient] All control plane components are healthy after 20.003530 seconds
[uploadconfig] storing the configuration used in ConfigMap "kubeadm-config" in the "kube-system" Namespace
[kubelet] Creating a ConfigMap "kubelet-config-1.12" in namespace kube-system with the configuration for the kubelets in the cluster
#给Master设置一个labele且设置一个taint
[markmaster] Marking the node k8s-master as master by adding the label "node-role.kubernetes.io/master=''"
[markmaster] Marking the node k8s-master as master by adding the taints [node-role.kubernetes.io/master:NoSchedule]
#集群的一些基础设置
[patchnode] Uploading the CRI Socket information "/var/run/dockershim.sock" to the Node API object "k8s-master" as an annotation
#设置了一个引导令牌，在节点加入时使用
[bootstraptoken] using token: mwfr7m.57rmd56ghjyu0716
[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] configured RBAC rules to allow certificate rotation for all node client certificates in the cluster
[bootstraptoken] creating the "cluster-info" ConfigMap in the "kube-public" namespace
[addons] Applied essential addon: CoreDNS
[addons] Applied essential addon: kube-proxy
#提示master已初始化成功
Your Kubernetes master has initialized successfully!

To start using your cluster, you need to run the following as a regular user:
#需要执行下面三条命令
  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:
  https://kubernetes.io/docs/concepts/cluster-administration/addons/

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

  kubeadm join 10.3.1.20:6443 --token mwfr7m.57rmd56ghjyu0716 --discovery-token-ca-cert-hash sha256:8fbd33519b0203e9aa03cc882cb5489b5e6ad455f97581b1abf8ceb1dca8f622

#把上面kubeadm join这一句话把这个记录下来，否则以后找起来有点麻烦，在node端加入时用到。

初始化完成，一台Master节点就部署好了，初始化过程中需要一定时间来pull镜像，也可以使用下面的命令提前下载好镜像：

root@k8s-master:~# kubeadm  config images pull 

[config/images] Pulled k8s.gcr.io/kube-apiserver:v1.12.0
[config/images] Pulled k8s.gcr.io/kube-controller-manager:v1.12.0
[config/images] Pulled k8s.gcr.io/kube-scheduler:v1.12.0
[config/images] Pulled k8s.gcr.io/kube-proxy:v1.12.0
[config/images] Pulled k8s.gcr.io/pause:3.1
[config/images] Pulled k8s.gcr.io/etcd:3.2.24
[config/images] Pulled k8s.gcr.io/coredns:1.2.2

#
root@k8s-master:~# docker images
REPOSITORY                           TAG                 IMAGE ID            CREATED             SIZE
k8s.gcr.io/kube-apiserver            v1.12.0             ab60b017e34f        16 hours ago        194 MB
k8s.gcr.io/kube-controller-manager   v1.12.0             07e068033cf2        16 hours ago        164 MB
k8s.gcr.io/kube-scheduler            v1.12.0             5a1527e735da        16 hours ago        58.3 MB
k8s.gcr.io/kube-proxy                v1.12.0             9c3a9d3f09a0        16 hours ago        96.6 MB
k8s.gcr.io/etcd                      3.2.24              3cab8e1b9802        7 days ago          220 MB
k8s.gcr.io/coredns                   1.2.2               367cdc8433a4        4 weeks ago         39.2 MB
k8s.gcr.io/pause                     3.1                 da86e6ba6ca1        9 months ago        742 kB

• 根据提示执行：

  root@k8s-master:~# mkdir -p $HOME/.kube
  root@k8s-master:~# sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
  root@k8s-master:~# sudo chown $(id -u):$(id -g) $HOME/.kube/config

  在Node上操作

  在所有Node上使用kubeadm join加入集群：

#确保swap已关闭
#复制在master节点上记录下的那句话，以加入集群
root@k8s-node01:~# kubeadm join 10.3.1.20:6443 --token mwfr7m.57rmd56ghjyu0716 --discovery-token-ca-cert-hash sha256:8fbd33519b0203e9aa03cc882cb5489b5e6ad455f97581b1abf8ceb1dca8f622

输出如下信息：

#加入时也会做一些预检
[preflight] running pre-flight checks
    [WARNING RequiredIPVSKernelModulesAvailable]: the IPVS proxier will not be used, because the following required kernel modules are not loaded: [ip_vs_rr ip_vs_wrr ip_vs_sh ip_vs] or no builtin kernel ipvs support: map[ip_vs:{} ip_vs_rr:{} ip_vs_wrr:{} ip_vs_sh:{} nf_conntrack_ipv4:{}]
you can solve this problem with following methods:
 1. Run 'modprobe -- ' to load missing kernel modules;
2. Provide the missing builtin kernel ipvs support

[discovery] Trying to connect to API Server "10.3.1.20:6443"
[discovery] Created cluster-info discovery client, requesting info from "https://10.3.1.20:6443"
[discovery] Requesting info from "https://10.3.1.20:6443" 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 "10.3.1.20:6443"
[discovery] Successfully established connection with API Server "10.3.1.20:6443"
[kubelet] Downloading configuration for the kubelet from the "kubelet-config-1.12" ConfigMap in the kube-system namespace
[kubelet] Writing kubelet configuration to file "/var/lib/kubelet/config.yaml"
[kubelet] Writing kubelet environment file with flags to file "/var/lib/kubelet/kubeadm-flags.env"
[preflight] Activating the kubelet service
[tlsbootstrap] Waiting for the kubelet to perform the TLS Bootstrap...
[patchnode] Uploading the CRI Socket information "/var/run/dockershim.sock" to the Node API object "k8s-node01" as an annotation

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 master to see this node join the cluster.

init完后，节点已加入群集。

最后，在master节点查看：

root@k8s-master:~# kubectl get node
NAME          STATUS     ROLES    AGE     VERSION
k8s-master    NotReady   master   6m39s   v1.12.0
k8s-node01   NotReady   <none>   4m31s   v1.12.0
k8s-node02   NotReady   <none>   97s     v1.12.0

去除master的taint，使用master也能被调度pod

root@k8s-master:~# kubectl taint nodes k8s-master node-role.kubernetes.io/master-
node/k8s-master untainted

安装CNI插件

各Node节点处于"NotReady" ，需要安装一个CNI网络插件：

root@k8s-master:~#  kubectl apply -f https://docs.projectcalico.org/v3.1/getting-started/kubernetes/installation/hosted/kubeadm/1.7/calico.yaml
configmap/calico-config configured
daemonset.extensions/calico-etcd created
service/calico-etcd created
daemonset.extensions/calico-node created
deployment.extensions/calico-kube-controllers created
clusterrolebinding.rbac.authorization.k8s.io/calico-cni-plugin created
clusterrole.rbac.authorization.k8s.io/calico-cni-plugin created
serviceaccount/calico-cni-plugin created
clusterrolebinding.rbac.authorization.k8s.io/calico-kube-controllers created
clusterrole.rbac.authorization.k8s.io/calico-kube-controllers created
serviceaccount/calico-kube-controllers unchanged
root@k8s-master:~# 

几分钟后，各Node全部Ready：

#各节点已正常运行
root@k8s-master:~# kubectl get node
NAME         STATUS   ROLES    AGE   VERSION
k8s-master   Ready    master   1h   v1.12.0
k8s-node01   Ready    <none>   1h   v1.12.0
k8s-node02   Ready    <none>   1h   v1.12.0

至此，所有组件全部运行：

root@k8s-master:~# kubectl get pod -n kube-system
NAME                                       READY   STATUS    RESTARTS   AGE
calico-etcd-d7v6w                          1/1     Running   0          3m21s
calico-kube-controllers-75fb4f8996-dg7hd   1/1     Running   0          3m20s
calico-node-794nd                          2/2     Running   0          3m19s
calico-node-b852z                          2/2     Running   0          3m19s
calico-node-z7f4n                          2/2     Running   0          3m19s
coredns-576cbf47c7-7svmm                   1/1     Running   0          15h
coredns-576cbf47c7-kzbv2                   1/1     Running   0          15h
etcd-k8s-master                            1/1     Running   0          15h
kube-apiserver-k8s-master                  1/1     Running   0          15h
kube-controller-manager-k8s-master         1/1     Running   0          15h
kube-proxy-7n5z9                           1/1     Running   0          15h
kube-proxy-rwq9g                           1/1     Running   0          15h
kube-proxy-v7qnx                           1/1     Running   0          15h
kube-scheduler-k8s-master                  1/1     Running   0          15h
root@k8s-master:~#

测试集群

• 配置kubectl的命令补全功能
  命令补全功能由安装包"bash-completion"提供，Ubuntu系统中默认已安装。

  当前shell生效：
  source <(kubectl completion bash)
  永久生效：
  echo "source <(kubectl completion bash)" >> ~/.bashrc

• 启动一个pod验证集群是否正常运行。

#run一个deployment
kubectl run -h
Usage:
  kubectl run NAME --image=image [--env="key=value"] [--port=port] [--replicas=replicas] [--dry-run=bool]
[--overrides=inline-json] [--command] -- [COMMAND] [args...] [options]

启动一个nginx

kubectl run nginx --image=nginx:1.10 --port=80
deployment.apps/nginx created
#查看
root@k8s-master:~# kubectl get pod -w -o wide
NAME                     READY   STATUS              RESTARTS   AGE   IP       NODE         NOMINATED NODE
nginx-787b58fd95-p9jwl   0/1     ContainerCreating   0          59s   <none>   k8s-node02   <none>
nginx-787b58fd95-p9jwl   1/1   Running   0     70s   192.168.58.193   k8s-node02   <none>

• 测试nginx正常访问

  root@k8s-master:~# curl  -I 192.168.58.193
  HTTP/1.1 200 OK
  Server: nginx/1.10.3
  Date: Sat, 29 Sep 2018 02:42:06 GMT
  Content-Type: text/html
  Content-Length: 612
  Last-Modified: Tue, 31 Jan 2017 15:01:11 GMT
  Connection: keep-alive
  ETag: "5890a6b7-264"
  Accept-Ranges: bytes

• 把nginx暴露一个端口出来，以使集群之外能访问

  kubectl expose -h
  Usage:
  kubectl expose (-f FILENAME | TYPE NAME) [--port=port] [--protocol=TCP|UDP|SCTP] [--target-port=number-or-name]
  [--name=name] [--external-ip=external-ip-of-service] [--type=type] [options]

  root@k8s-master:~# kubectl expose deployment nginx --port=801 --target-port=80 --type=NodePort --name nginx-svc
  service/nginx-svc exposed
  root@k8s-master:~# 

• 查看服务：

  root@k8s-master:~# kubectl get svc
  NAME         TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)         AGE
  kubernetes   ClusterIP   10.96.0.1       <none>        443/TCP         16h
  nginx-svc    NodePort    10.100.84.207   <none>        801:30864/TCP   25s

现在可以访问任意Node的30864端口访问到nginx服务：

root@k8s-node01:~# curl 10.3.1.21:30864

<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>
    body {
        width: 35em;
        margin: 0 auto;
        font-family: Tahoma, Verdana, Arial, sans-serif;
    }
</style>
</head>
<body>

如果发现哪个某个Node端口无法访问，则设置默认FORWARD规则为ACCEPT

 iptables -P FORWARD ACCEPT

kubeadm集群配置到此完成，可参考官方文档