使用Kubeadm(1.13+)快速搭建Kubernetes集群

时间 2019-11-16

标签使用 kubeadm 1.13 快速搭建 kubernetes 集群栏目负载均衡繁體版

原文原文链接

Kubeadm是管理集群生命周期的重要工具，从建立到配置再到升级，Kubeadm处理现有硬件上的生产集群的引导，并以最佳实践方式配置核心Kubernetes组件，以便为新节点提供安全而简单的链接流程并支持轻松升级。随着Kubernetes 1.13 的发布，如今Kubeadm正式成为GA。html

准备

首先准备2台虚拟机（CPU最少2核），我是使用Hyper-V建立的2台Ubuntu18.04虚拟机，IP和机器名以下：node

172.17.20.210 masternginx

172.17.20.211 node1docker

禁用Swap

Kubernetes 1.8开始要求必须禁用Swap，若是不关闭，默认配置下kubelet将没法启动。bootstrap

编辑/etc/fstab文件：ubuntu

sudo vim /etc/fstab

UUID=8be04efd-f7c5-11e8-be8b-00155d000500 / ext4 defaults 0 0
UUID=C0E3-6A72 /boot/efi vfat defaults 0 0
#/swap.img      none    swap    sw      0       0

如上，将/swap.img所在的行注释掉，而后运行：vim

sudo swapoff -a

(可选)DNS配置

在Ubuntu18.04+版本中，DNS由systemd全面接管，接口监听在127.0.0.53:53，配置文件在/etc/systemd/resolved.conf中。api

有时候会致使没法解析域名的问题，可以使用以下2种方式来解决：安全

1.最简单的就是关闭systemd-resolvd服务bash

sudo systemctl stop systemd-resolved
sudo systemctl disable systemd-resolved

而后手动修改/etc/resolv.conf文件就能够了。

2.更加推荐的作法是修改systemd-resolv的设置：

sudo vim /etc/systemd/resolved.conf

# 修改成以下
[Resolve]
DNS=1.1.1.1 1.0.0.1
#FallbackDNS=
#Domains=
LLMNR=no
#MulticastDNS=no
#DNSSEC=no
#Cache=yes
#DNSStubListener=yes

DNS=设置的是域名解析服务器的IP地址，这里分别设为1.1.1.1和1.0.0.1
LLMNR=设置的是禁止运行LLMNR(Link-Local Multicast Name Resolution)，不然systemd-resolve会监听5535端口。

安装Docker

Kubernetes从1.6开始使用CRI(Container Runtime Interface)容器运行时接口。默认的容器运行时仍然是Docker，是使用kubelet中内置dockershim CRI来实现的。

Docker的安装能够参考以前的博客：Docker初体验。

须要注意的是，Kubernetes 1.13已经针对Docker的1.11.1, 1.12.1, 1.13.1, 17.03, 17.06, 17.09, 18.06等版本作了验证，最低支持的Docker版本是1.11.1，最高支持是18.06，而Docker最新版本已是18.09了，故咱们安装时须要指定版本为18.06.1-ce：
sudo apt install docker-ce=18.06.1~ce~3-0~ubuntu

安装kubeadm, kubelet 和 kubectl

部署以前，咱们须要安装三个包：

kubeadm: 引导启动k8s集群的命令行工具。
kubelet: 在群集中全部节点上运行的核心组件, 用来执行如启动pods和containers等操做。
kubectl: 操做集群的命令行工具。

首先添加apt-key：

sudo apt update && sudo apt install -y apt-transport-https curl
curl -s https://mirrors.aliyun.com/kubernetes/apt/doc/apt-key.gpg | sudo apt-key add -

添加kubernetes源：

sudo vim /etc/apt/sources.list.d/kubernetes.list

deb https://mirrors.aliyun.com/kubernetes/apt/ kubernetes-xenial main

安装：

sudo apt update
sudo apt install -y kubelet kubeadm kubectl
sudo apt-mark hold kubelet kubeadm kubectl

使用kubeadm建立一个单Master集群

初始化Master节点

K8s的控制面板组件运行在Master节点上，包括etcd和API server（Kubectl即是经过API server与k8s通讯）。

在执行初始化以前，咱们还有一下3点须要注意：

1.选择一个网络插件，并检查它是否须要在初始化Master时指定一些参数，好比咱们可能须要根据选择的插件来设置--pod-network-cidr参数。参考：Installing a pod network add-on。

2.kubeadm使用eth0的默认网络接口（一般是内网IP）作为Master节点的advertise address，若是咱们想使用不一样的网络接口，可使用--apiserver-advertise-address=<ip-address>参数来设置。若是适应IPv6，则必须使用IPv6d的地址，如：--apiserver-advertise-address=fd00::101。

3.使用kubeadm config images pull来预先拉取初始化须要用到的镜像，用来检查是否能链接到Kubenetes的Registries。

Kubenetes默认Registries地址是k8s.gcr.io，很明显，在国内并不能访问gcr.io，所以在kubeadm v1.13以前的版本，安装起来很是麻烦，可是在1.13版本中终于解决了国内的痛点，其增长了一个--image-repository参数，默认值是k8s.gcr.io，咱们将其指定为国内镜像地址：registry.aliyuncs.com/google_containers，其它的就能够彻底按照官方文档来愉快的玩耍了。

其次，咱们还须要指定--kubernetes-version参数，由于它的默认值是stable-1，会致使从https://dl.k8s.io/release/stable-1.txt下载最新的版本号，咱们能够将其指定为固定版本（最新版：v1.13.1）来跳过网络请求。

如今，咱们就来试一下：

# 使用calico网络 --pod-network-cidr=192.168.0.0/16
sudo kubeadm init --image-repository registry.aliyuncs.com/google_containers --kubernetes-version v1.13.1 --pod-network-cidr=192.168.0.0/16

# 输出
[init] Using Kubernetes version: v1.13.1
[preflight] Running pre-flight checks
[preflight] Pulling images required for setting up a Kubernetes cluster
[preflight] This might take a minute or two, depending on the speed of your internet connection
[preflight] You can also perform this action in beforehand using 'kubeadm config images pull'
[kubelet-start] Writing kubelet environment file with flags to file "/var/lib/kubelet/kubeadm-flags.env"
[kubelet-start] Writing kubelet configuration to file "/var/lib/kubelet/config.yaml"
[kubelet-start] Activating the kubelet service
[certs] Using certificateDir folder "/etc/kubernetes/pki"
[certs] Generating "ca" certificate and key
[certs] Generating "apiserver" certificate and key
[certs] apiserver serving cert is signed for DNS names [master kubernetes kubernetes.default kubernetes.default.svc kubernetes.default.svc.cluster.local] and IPs [10.96.0.1 172.17.20.210]
[certs] Generating "apiserver-kubelet-client" certificate and key
[certs] Generating "front-proxy-ca" certificate and key
[certs] Generating "front-proxy-client" certificate and key
[certs] Generating "etcd/ca" certificate and key
[certs] Generating "etcd/peer" certificate and key
[certs] etcd/peer serving cert is signed for DNS names [master localhost] and IPs [172.17.20.210 127.0.0.1 ::1]
[certs] Generating "etcd/server" certificate and key
[certs] etcd/server serving cert is signed for DNS names [master localhost] and IPs [172.17.20.210 127.0.0.1 ::1]
[certs] Generating "etcd/healthcheck-client" certificate and key
[certs] Generating "apiserver-etcd-client" certificate and key
[certs] Generating "sa" key and public key
[kubeconfig] Using kubeconfig folder "/etc/kubernetes"
[kubeconfig] Writing "admin.conf" kubeconfig file
[kubeconfig] Writing "kubelet.conf" kubeconfig file
[kubeconfig] Writing "controller-manager.conf" kubeconfig file
[kubeconfig] Writing "scheduler.conf" kubeconfig file
[control-plane] Using manifest folder "/etc/kubernetes/manifests"
[control-plane] Creating static Pod manifest for "kube-apiserver"
[control-plane] Creating static Pod manifest for "kube-controller-manager"
[control-plane] Creating static Pod manifest for "kube-scheduler"
[etcd] Creating static Pod manifest for local etcd in "/etc/kubernetes/manifests"
[wait-control-plane] Waiting for the kubelet to boot up the control plane as static Pods from directory "/etc/kubernetes/manifests". This can take up to 4m0s
[kubelet-check] Initial timeout of 40s passed.
[apiclient] All control plane components are healthy after 42.003645 seconds
[uploadconfig] storing the configuration used in ConfigMap "kubeadm-config" in the "kube-system" Namespace
[kubelet] Creating a ConfigMap "kubelet-config-1.13" in namespace kube-system with the configuration for the kubelets in the cluster
[patchnode] Uploading the CRI Socket information "/var/run/dockershim.sock" to the Node API object "master" as an annotation
[mark-control-plane] Marking the node master as control-plane by adding the label "node-role.kubernetes.io/master=''"
[mark-control-plane] Marking the node master as control-plane by adding the taints [node-role.kubernetes.io/master:NoSchedule]
[bootstrap-token] Using token: 6pkrlg.8glf2fqpuf3i489m
[bootstrap-token] Configuring bootstrap tokens, cluster-info ConfigMap, RBAC Roles
[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

Your Kubernetes master 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

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 172.17.20.210:6443 --token 6pkrlg.8glf2fqpuf3i489m --discovery-token-ca-cert-hash sha256:eebfe256113bee397b218ba832f412273ae734bd4686241fb910885d26efd222

此次很是顺利的就部署成功了，若是咱们想使用非root用户操做kubectl，可使用如下命令，这也是kubeadm init输出的一部分：

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

安装网络插件

为了让Pods间能够相互通讯，咱们必须安装一个网络插件，而且必须在部署任何应用以前安装，CoreDNS也是在网络插件安装以后才会启动的。

网络的插件完整列表，请参考 Networking and Network Policy。

在安装以前，咱们先查看一下当前Pods的状态：

kubectl get pods --all-namespaces

# 输出
NAMESPACE     NAME                             READY   STATUS    RESTARTS   AGE
kube-system   coredns-78d4cf999f-6pgfr         0/1     Pending   0          87s
kube-system   coredns-78d4cf999f-m9kgs         0/1     Pending   0          87s
kube-system   etcd-master                      1/1     Running   0          47s
kube-system   kube-apiserver-master            1/1     Running   0          38s
kube-system   kube-controller-manager-master   1/1     Running   0          55s
kube-system   kube-proxy-mkg24                 1/1     Running   0          87s
kube-system   kube-scheduler-master            1/1     Running   0          41s

如上，能够看到CoreDND的状态是Pending，这是由于咱们尚未安装网络插件。

Calico是一个纯三层的虚拟网络方案，Calico 为每一个容器分配一个 IP，每一个 host 都是 router，把不一样 host 的容器链接起来。与 VxLAN 不一样的是，Calico 不对数据包作额外封装，不须要 NAT 和端口映射，扩展性和性能都很好。

默认状况下，Calico网络插件使用的的网段是192.168.0.0/16，在init的时候，咱们已经经过--pod-network-cidr=192.168.0.0/16来适配Calico，固然你也能够修改calico.yml文件来指定不一样的网段。

可使用以下命令命令来安装Canal插件：

kubectl apply -f https://docs.projectcalico.org/v3.3/getting-started/kubernetes/installation/hosted/rbac-kdd.yaml
kubectl apply -f https://docs.projectcalico.org/v3.3/getting-started/kubernetes/installation/hosted/kubernetes-datastore/calico-networking/1.7/calico.yaml

# 上面的calico.yaml会去quay.io拉取镜像，若是没法拉取，可以使用下面的国内镜像
kubectl apply -f http://mirror.faasx.com/k8s/calico/v3.3.2/rbac-kdd.yaml
kubectl apply -f http://mirror.faasx.com/k8s/calico/v3.3.2/calico.yaml

关于更多Canal的信息能够查看Calico官方文档：kubeadm quickstart。

稍等片刻，再使用kubectl get pods --all-namespaces命令来查看网络插件的安装状况：

kubectl get pods --all-namespaces

# 输出
NAMESPACE     NAME                             READY   STATUS    RESTARTS   AGE
kube-system   calico-node-x96gn                2/2     Running   0          47s
kube-system   coredns-78d4cf999f-6pgfr         1/1     Running   0          54m
kube-system   coredns-78d4cf999f-m9kgs         1/1     Running   0          54m
kube-system   etcd-master                      1/1     Running   3          53m
kube-system   kube-apiserver-master            1/1     Running   3          53m
kube-system   kube-controller-manager-master   1/1     Running   3          53m
kube-system   kube-proxy-mkg24                 1/1     Running   2          54m
kube-system   kube-scheduler-master            1/1     Running   3          53m

如上，STATUS所有变为了Running，表示安装成功，接下来就能够加入其余节点以及部署应用了。

Master隔离

默认状况下，因为安全缘由，集群并不会将pods部署在Master节点上。可是在开发环境下，咱们可能就只有一个Master节点，这时可使用下面的命令来解除这个限制：

kubectl taint nodes --all node-role.kubernetes.io/master-

## 输出
node/master untainted

加入工做节点

要为群集添加工做节点，须要为每台计算机执行如下操做：

SSH到机器
成为root用户，(如: sudo su -)
运行上面的kubeadm init命令输出的：kubeadm join --token <token> <master-ip>:<master-port> --discovery-token-ca-cert-hash sha256:<hash>

若是咱们忘记了Master节点的加入token，可使用以下命令来查看：

kubeadm token list

# 输出
TOKEN                     TTL       EXPIRES                USAGES                   DESCRIPTION                                                EXTRA GROUPS
6pkrlg.8glf2fqpuf3i489m   22h       2018-12-07T13:46:33Z   authentication,signing   The default bootstrap token generated by 'kubeadm init'.   system:bootstrappers:kubeadm:default-node-token

默认状况下，token的有效期是24小时，若是咱们的token已通过期的话，可使用如下命令从新生成：

kubeadm token create

# 输出
u2mt59.tyqpo0v5wf05lx2q

若是咱们也没有--discovery-token-ca-cert-hash的值，可使用如下命令生成：

openssl x509 -pubkey -in /etc/kubernetes/pki/ca.crt | openssl rsa -pubin -outform der 2>/dev/null | openssl dgst -sha256 -hex | sed 's/^.* //'

# 输出
eebfe256113bee397b218ba832f412273ae734bd4686241fb910885d26efd222

如今，咱们登陆到工做节点服务器，而后运行以下命令加入集群（这也是上面init输出的一部分）：

sudo kubeadm join 172.17.20.210:6443 --token 6pkrlg.8glf2fqpuf3i489m --discovery-token-ca-cert-hash sha256:eebfe256113bee397b218ba832f412273ae734bd4686241fb910885d26efd222

# 输出
[sudo] password for raining: 
[preflight] Running pre-flight checks
[discovery] Trying to connect to API Server "172.17.20.210:6443"
[discovery] Created cluster-info discovery client, requesting info from "https://172.17.20.210:6443"
[discovery] Requesting info from "https://172.17.20.210:6443" 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 "172.17.20.210:6443"
[discovery] Successfully established connection with API Server "172.17.20.210:6443"
[join] Reading configuration from the cluster...
[join] FYI: You can look at this config file with 'kubectl -n kube-system get cm kubeadm-config -oyaml'
[kubelet] Downloading configuration for the kubelet from the "kubelet-config-1.13" ConfigMap in the kube-system namespace
[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] 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 "node1" 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.

等待一会，咱们能够在Master节点上使用kubectl get nodes命令来查看节点的状态：

kubectl get nodes

# 输出
NAME     STATUS   ROLES    AGE   VERSION
master   Ready    master   17m   v1.13.1
node1    Ready    <none>   15m   v1.13.1

如上所有Ready，大功告成，咱们能够运行一些命令来测试一下集群是否正常。

测试

首先验证kube-apiserver, kube-controller-manager, kube-scheduler, pod network 是否正常：

# 部署一个 Nginx Deployment，包含两个Pod
# https://kubernetes.io/docs/concepts/workloads/controllers/deployment/
kubectl create deployment nginx --image=nginx:alpine
kubectl scale deployment nginx --replicas=2

# 验证Nginx Pod是否正确运行，而且会分配192.168.开头的集群IP
kubectl get pods -l app=nginx -o wide

# 输出以下：
NAME                     READY   STATUS    RESTARTS   AGE   IP            NODE    NOMINATED NODE   READINESS GATES
nginx-54458cd494-p8jzs   1/1     Running   0          31s   192.168.1.2   node1   <none>           <none>
nginx-54458cd494-v2m4b   1/1     Running   0          24s   192.168.1.3   node1   <none>           <none>

再验证一下kube-proxy是否正常：

# 以 NodePort 方式对外提供服务 https://kubernetes.io/docs/concepts/services-networking/connect-applications-service/
kubectl expose deployment nginx --port=80 --type=NodePort

# 查看集群外可访问的Port
kubectl get services nginx

# 输出
NAME    TYPE       CLUSTER-IP     EXTERNAL-IP   PORT(S)        AGE
nginx   NodePort   10.110.49.49   <none>        80:31899/TCP   4s

# 能够经过任意 NodeIP:Port 在集群外部访问这个服务，本示例中部署的2台集群IP分别是172.17.20.210和172.17.20.211
curl http://172.17.20.210:31899
curl http://172.17.20.211:31899

最后验证一下dns, pod network是否正常：

# 运行Busybox并进入交互模式
kubectl run -it curl --image=radial/busyboxplus:curl

# 输入`nslookup nginx`查看是否能够正确解析出集群内的IP，已验证DNS是否正常
[ root@curl-66959f6557-6sfqh:/ ]$ nslookup nginx

# 输出
Server:    10.96.0.10
Address 1: 10.96.0.10 kube-dns.kube-system.svc.cluster.local

Name:      nginx
Address 1: 10.110.49.49 nginx.default.svc.cluster.local

# 经过服务名进行访问，验证kube-proxy是否正常
[ root@curl-66959f6557-6sfqh:/ ]$ curl http://nginx/

# 输出以下：
# <!DOCTYPE html> ---省略

# 分别访问一下2个Pod的内网IP，验证跨Node的网络通讯是否正常
[ root@curl-66959f6557-6sfqh:/ ]$ curl http://192.168.1.2/
[ root@curl-66959f6557-6sfqh:/ ]$ curl http://192.168.1.3/

验证经过，集群搭建成功，接下来咱们就能够参考官方文档来部署其余服务，愉快的玩耍了。

卸载集群

想要撤销kubeadm执行的操做，首先要排除节点，并确保该节点为空, 而后再将其关闭。

在Master节点上运行：

kubectl drain <node name> --delete-local-data --force --ignore-daemonsets
kubectl delete node <node name>

而后在须要移除的节点上，重置kubeadm的安装状态：

sudo kubeadm reset

若是你想从新配置集群，使用新的参数从新运行kubeadm init或者kubeadm join便可。