用 kubeadm 部署生产级 k8s 集群

概述

kubeadm 已⽀持集群部署，且在1.13 版本中 GA，⽀持多 master，多 etcd 集群化部署，它也是官⽅最为推荐的部署⽅式，⼀来是由它的 sig 组来推进的，⼆来 kubeadm 在很多⽅⾯确实很好的利⽤了 kubernetes 的许多特性，接下来⼏篇我们来实践并了解下它的魅⼒。

⽬标

1. 通过 kubeadm 搭建⾼可⽤ kubernetes 集群，并新建管理⽤户

2. 为后续做版本升级演示，此处使⽤1.13.1版本，到下⼀篇再升级到 v1.14

3. kubeadm 的原理解读

本⽂主要介绍 kubeadm 对⾼可⽤集群的部署

kubeadm 部署 k8s v1.13 ⾼可⽤集群

⽅式有两种

• Stacked etcd topology

• 即每台 etcd 各⾃独⽴，分别部署在 3 台 master 上，互不通信，优点是简单，缺点是缺乏 etcd ⾼可⽤性

• 需要⾄少 4 台机器（3master 和 etcd,1node)

• External etcd topology

• 即采⽤集群外 etcd 拓扑结构，这样的冗余性更好，但需要⾄少7台机器（3master,3etcd,1node)

• ⽣产环境建议采⽤该⽅案

• 本⽂也采⽤这个拓扑

步骤

• 环境准备

• 安装组件：docker,kubelet,kubeadm（所有节点）

• 使⽤上述组件部署 etcd ⾼可⽤集群

• 部署 master

• 加⼊node

• ⽹络安装

• 验证

• 总结

机环境准备

• 系统环境

#操作系统版本（⾮必须，仅为此处案例）
$cat /etc/redhat-release
CentOS Linux release 7.2.1511 (Core)
#内核版本（⾮必须，仅为此处案例）
$uname -r
4.17.8-1.el7.elrepo.x86_64

#数据盘开启ftype（在每台节点上执⾏）
umount /data
mkfs.xfs -n ftype=1 -f /dev/vdb
#禁⽤swap
swapoff -a
sed -i "s#^/swapfile#\#/swapfile#g" /etc/fstab
mount -a

docker,kubelet,kubeadm 的安装（所有节点）

• 安装运⾏时（docker）

  • k8s1.13 版本根据官⽅建议，暂不采⽤最新的 18.09，这⾥我们采⽤18.06，安装时需指定版本

  • 来源：kubeadm now properly recognizes Docker 18.09.0 and newer, but still treats 18.06 as the default supported version.

  • 安装脚本如下（在每台节点上执⾏）：

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

yum makecache fast

yum install -y --setopt=obsoletes=0 \
      docker-ce-18.06.1.ce-3.el7

systemctl start docker
systemctl enable docker

• 安装 kubeadm,kubelet,kubectl

  • 官⽅的 Google yum 源⽆法从国内服务器上直接下载，所以可先在其他渠道下载好，在上传到服务器上

cat <<EOF > /etc/yum.repos.d/kubernetes.repo

 * 本地安装

# 禁⽤selinux

 * ⽹络修复，已知 centos7 会因 iptables 被绕过⽽将流量错误路由，因此需确保sysctl 配置中的 net.bridge.bridgenf-call-iptables 被设置为 1

cat <<EOF > /etc/sysctl.d/k8s.conf

使⽤上述组件部署 etcd ⾼可⽤集群

1. 在 etcd 节点上，将 etcd 服务设置为由 kubelet 启动管理

cat << EOF > /etc/systemd/system/kubelet.service.d/20-etcd-service-manager.conf

2. 给每台 etcd 主机⽣成 kubeadm 配置⽂件，确保每台主机运⾏⼀个 etcd 实例:在 etcd1（即上述的 hosts0）上执⾏上述

命令，可以在 /tmp ⽬录下看到⼏个主机名的⽬录

# Update HOST0, HOST1, and HOST2 with the IPs or resolvable names of your hosts
export HOST0=10.10.184.226
export HOST1=10.10.213.222
export HOST2=10.10.239.108

# Create temp directories to store files that will end up on other hosts.
mkdir -p /tmp/${HOST0}/ /tmp/${HOST1}/ /tmp/${HOST2}/

ETCDHOSTS=(${HOST0} ${HOST1} ${HOST2})
NAMES=("infra0" "infra1" "infra2")

for i in "${!ETCDHOSTS[@]}"; do
HOST=${ETCDHOSTS[$i]}
NAME=${NAMES[$i]}
cat << EOF > /tmp/${HOST}/kubeadmcfg.yaml
apiVersion: "kubeadm.k8s.io/v1beta1"
kind: ClusterConfiguration
etcd:
      local:
            serverCertSANs:
            - "${HOST}"
            peerCertSANs:
            - "${HOST}"
            extraArgs:
                  initial-cluster:
${NAMES[0]}=https://${ETCDHOSTS[0]}:2380,${NAMES[1]}=https://${ETCDHOSTS[1]}:2380,${N
AMES[2]}=https://${ETCDHOSTS[2]}:2380
                  initial-cluster-state: new
                  name: ${NAME}
                  listen-peer-urls: https://${HOST}:2380
                  listen-client-urls: https://${HOST}:2379
                  advertise-client-urls: https://${HOST}:2379
                  initial-advertise-peer-urls: https://${HOST}:2380
EOF
done

3. 制作CA：在host0上执⾏命令⽣成证书，它将创建两个⽂件：/etc/kubernetes/pki/etcd/ca.crt/etc/kubernetes/pki/etcd/ca.key (这⼀步需要翻墙)

[root@10-10-184-226 ~]# kubeadm init phase certs etcd-ca
[certs] Generating "etcd/ca" certificate and key

4. 在 host0 上给每个 etcd 节点⽣成证书：

export HOST0=10.10.184.226
export HOST1=10.10.213.222
export HOST2=10.10.239.108
kubeadm init phase certs etcd-server --config=/tmp/${HOST2}/kubeadmcfg.yaml
kubeadm init phase certs etcd-peer --config=/tmp/${HOST2}/kubeadmcfg.yaml
kubeadm init phase certs etcd-healthcheck-client --
config=/tmp/${HOST2}/kubeadmcfg.yaml
kubeadm init phase certs apiserver-etcd-client --config=/tmp/${HOST2}/kubeadmcfg.yaml
cp -R /etc/kubernetes/pki /tmp/${HOST2}/
# cleanup non-reusable certificates
find /etc/kubernetes/pki -not -name ca.crt -not -name ca.key -type f -delete

kubeadm init phase certs etcd-server --config=/tmp/${HOST1}/kubeadmcfg.yaml
kubeadm init phase certs etcd-peer --config=/tmp/${HOST1}/kubeadmcfg.yaml
kubeadm init phase certs etcd-healthcheck-client --
config=/tmp/${HOST1}/kubeadmcfg.yaml
kubeadm init phase certs apiserver-etcd-client --config=/tmp/${HOST1}/kubeadmcfg.yaml
cp -R /etc/kubernetes/pki /tmp/${HOST1}/
find /etc/kubernetes/pki -not -name ca.crt -not -name ca.key -type f -delete

kubeadm init phase certs etcd-server --config=/tmp/${HOST0}/kubeadmcfg.yaml
kubeadm init phase certs etcd-peer --config=/tmp/${HOST0}/kubeadmcfg.yaml
kubeadm init phase certs etcd-healthcheck-client --
config=/tmp/${HOST0}/kubeadmcfg.yaml
kubeadm init phase certs apiserver-etcd-client --config=/tmp/${HOST0}/kubeadmcfg.yaml
# No need to move the certs because they are for HOST0

# clean up certs that should not be copied off this host
find /tmp/${HOST2} -name ca.key -type f -delete
find /tmp/${HOST1} -name ca.key -type f -delete

• 将证书和 kubeadmcfg.yaml 下发到各个 etcd 节点上效果为

/root/
└── kubeadmcfg.yaml
---
/etc/kubernetes/pki
├── apiserver-etcd-client.crt
├── apiserver-etcd-client.key
└── etcd
        ├── ca.crt
        ├── ca.key
        ├── healthcheck-client.crt
        ├── healthcheck-client.key
        ├── peer.crt
        ├── peer.key
        ├── server.crt
        └── server.key

5. ⽣成静态 pod manifest ,在 3 台 etcd 节点上分别执⾏：（需翻墙）

$ kubeadm init phase etcd local --config=/root/kubeadmcfg.yaml
[etcd] Creating static Pod manifest for local etcd in "/etc/kubernetes/manifests"

6. 检查 etcd 集群状态，⾄此 etcd 集群搭建完成

docker run --rm -it --net host -v /etc/kubernetes:/etc/kubernetes
k8s.gcr.io/etcd:3.2.24 etcdctl --cert-file /etc/kubernetes/pki/etcd/peer.crt --key�file /etc/kubernetes/pki/etcd/peer.key --ca-file /etc/kubernetes/pki/etcd/ca.crt --
endpoints https://${HOST0}:2379 cluster-health
member 9969ee7ea515cbd2 is healthy: got healthy result from
https://10.10.213.222:2379
member cad4b939d8dfb250 is healthy: got healthy result from
https://10.10.239.108:2379
member e6e86b3b5b495dfb is healthy: got healthy result from
https://10.10.184.226:2379
cluster is healthy

使⽤ kubeadm 部署 master

• 将任意⼀台 etcd 上的证书拷⻉到 master1 节点

export CONTROL_PLANE="ubuntu@10.0.0.7"
+scp /etc/kubernetes/pki/etcd/ca.crt "${CONTROL_PLANE}":
+scp /etc/kubernetes/pki/apiserver-etcd-client.crt "${CONTROL_PLANE}":
+scp /etc/kubernetes/pki/apiserver-etcd-client.key "${CONTROL_PLANE}":

• 在第⼀台 master 上编写配置⽂件 kubeadm-config.yaml 并初始化

apiVersion: kubeadm.k8s.io/v1beta1
kind: ClusterConfiguration
kubernetesVersion: stable
#kubernetesVersion: 1.13.1
#注意这⾥我们想先安装1.13.1再后续升级1.13.4所以直接声明版本号
apiServer:
   certSANs:
   - "k8s.paas.test"
controlPlaneEndpoint: "k8s.paas.test:6443"
etcd:
       external:
              endpoints:
              - https://10.10.184.226:2379
              - https://10.10.213.222:2379
              - https://10.10.239.108:2379
              caFile: /etc/kubernetes/pki/etcd/ca.crt
              certFile: /etc/kubernetes/pki/apiserver-etcd-client.crt
              keyFile: /etc/kubernetes/pki/apiserver-etcd-client.key
networking:
    podSubnet: "10.244.0.0/16"

注意：这⾥的 k8s.paas.test:6443 是⼀个 LB，如果没有可⽤虚拟 IP 来做

• 使⽤私有仓库（⾃定义镜像功能） kubeadm ⽀持通过修改配置⽂件中的参数来灵活定制集群初始化⼯作，如 imageRepository 可以设置镜像前缀，我们可以在将镜像传到⾃⼰内部私服上之后，编辑 kubeadm-config.yaml 中的该参数之后再执⾏ init

• 在 master1 上执⾏：kubeadm init --config kubeadm-config.yaml

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 k8s.paas.test:6443 --token f1oygc.3zlc31yjcut46prf --discovery�token-ca-cert-hash xx
  
  [root@k8s-m1 ~]
  $kubectl get node
  NAME STATUS ROLES AGE VERSION
  k8s-m1 NotReady master 4m54s v1.13.1

安装另外2台 master

• master1 上的 admin.conf 配置⽂件和 pki 相关证书拷⻉到另外 2 台 master 同样⽬录下如：

/etc/kubernetes/pki/ca.crt
/etc/kubernetes/pki/ca.key
/etc/kubernetes/pki/sa.key
/etc/kubernetes/pki/sa.pub
/etc/kubernetes/pki/front-proxy-ca.crt
/etc/kubernetes/pki/front-proxy-ca.key
/etc/kubernetes/pki/etcd/ca.crt
/etc/kubernetes/pki/etcd/ca.key (官⽅⽂档中此处需要拷⻉，但实际不需要)
/etc/kubernetes/admin.conf

注：官⽹⽂档少了两个⽂件/etc/kubernetes/pki/apiserver-etcd-client.crt/etc/kubernetes/pki/apiserver-etcdclient.key，不加 apiserver 会启动失败并报错：

Unable to create storage backend: config (&{ /registry []
/etc/kubernetes/pki/apiserver-etcd-client.key /etc/kubernetes/pki/apiserver-etcd�client.crt /etc/kubernetes/pki/etcd/ca.crt true 0xc000133c20 <nil> 5m0s 1m0s}),
err (open /etc/kubernetes/pki/apiserver-etcd-client.crt: no such file or
directory)

• 在 2 和 3 master 中执⾏加⼊：

  kubeadm join k8s.paas.test:6443 --token f1oygc.3zlc31yjcut46prf --discovery-token�ca-cert-hash sha256:078b63e29378fb6dcbedd80dd830b83e37521f294b4e3416cd77e854041d912f
--experimental-control-plane

加⼊ node 节点

[root@k8s-n1 ~]
$ kubeadm join k8s.paas.test:6443 --token f1oygc.3zlc31yjcut46prf --discovery-token�ca-cert-hash sha256:078b63e29378fb6dcbedd80dd830b83e37521f294b4e3416cd77e854041d912f
[preflight] Running pre-flight checks
[discovery] Trying to connect to API Server "k8s.paas.test:6443"
[discovery] Created cluster-info discovery client, requesting info from
"https://k8s.paas.test:6443"
[discovery] Requesting info from "https://k8s.paas.test: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 "k8s.paas.test:6443"
[discovery] Successfully established connection with API Server "k8s.paas.test: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 "k8s-n1" 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.

网络安装

kubectl apply -f
https://raw.githubusercontent.com/coreos/flannel/a70459be0084506e4ec919aa1c114638878d
b11b/Documentation/kube-flannel.yml
kubectl get pod --all-namespaces -o wide
NAMESPACE NAME READY STATUS RESTARTS AGE
IP NODE NOMINATED NODE READINESS GATES
kube-system coredns-86c58d9df4-dc4t2 1/1 Running 0 14m
172.17.0.3 k8s-m1 <none> <none>
kube-system coredns-86c58d9df4-jxv6v 1/1 Running 0 14m
172.17.0.2 k8s-m1 <none> <none>
kube-system kube-apiserver-k8s-m1 1/1 Running 0 13m
10.10.119.128 k8s-m1 <none> <none>
kube-system kube-apiserver-k8s-m2 1/1 Running 0 5m
10.10.76.80 k8s-m2 <none> <none>
kube-system kube-apiserver-k8s-m3 1/1 Running 0 4m58s
10.10.56.27 k8s-m3 <none> <none>
kube-system kube-controller-manager-k8s-m1 1/1 Running 0 13m
10.10.119.128 k8s-m1 <none> <none>
kube-system kube-controller-manager-k8s-m2 1/1 Running 0 5m
10.10.76.80 k8s-m2 <none> <none>
kube-system kube-controller-manager-k8s-m3 1/1 Running 0 4m58s
10.10.56.27 k8s-m3 <none> <none>
kube-system kube-flannel-ds-amd64-nvmtk 1/1 Running 0 44s
10.10.56.27 k8s-m3 <none> <none>
kube-system kube-flannel-ds-amd64-pct2g 1/1 Running 0 44s
10.10.76.80 k8s-m2 <none> <none>
kube-system kube-flannel-ds-amd64-ptv9z 1/1 Running 0 44s
10.10.119.128 k8s-m1 <none> <none>
kube-system kube-flannel-ds-amd64-zcv49 1/1 Running 0 44s
10.10.175.146 k8s-n1 <none> <none>
kube-system kube-proxy-9cmg2 1/1 Running 0 2m34s
10.10.175.146 k8s-n1 <none> <none>
kube-system kube-proxy-krlkf 1/1 Running 0 4m58s
10.10.56.27 k8s-m3 <none> <none>
kube-system kube-proxy-p9v66 1/1 Running 0 14m
10.10.119.128 k8s-m1 <none> <none>
kube-system kube-proxy-wcgg6 1/1 Running 0 5m
10.10.76.80 k8s-m2 <none> <none>
kube-system kube-scheduler-k8s-m1 1/1 Running 0 13m
10.10.119.128 k8s-m1 <none> <none>
kube-system kube-scheduler-k8s-m2 1/1 Running 0 5m
10.10.76.80 k8s-m2 <none> <none>
kube-system kube-scheduler-k8s-m3 1/1 Running 0 4m58s
10.10.56.27 k8s-m3 <none> <none>

安装完成

验证

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

$kubectl create deployment nginx --image=nginx:alpine
$kubectl get pods -l app=nginx -o wide
NAME READY STATUS RESTARTS AGE IP NODE
NOMINATED NODE READINESS GATES
nginx-54458cd494-r6hqm 1/1 Running 0 5m24s 10.244.4.2 k8s-n1
<none> <none>

• kube-proxy 验证

$kubectl expose deployment nginx --port=80 --type=NodePort
service/nginx exposed

[root@k8s-m1 ~]
$kubectl get svc
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 122m
nginx NodePort 10.108.192.221 <none> 80:30992/TCP 4s
[root@k8s-m1 ~]
$kubectl get pods -l app=nginx -o wide
NAME READY STATUS RESTARTS AGE IP NODE
NOMINATED NODE READINESS GATES
nginx-54458cd494-r6hqm 1/1 Running 0 6m53s 10.244.4.2 k8s-n1
<none> <none>

$curl -I k8s-n1:30992
HTTP/1.1 200 OK

• 验证 dns,pod ⽹络状态

kubectl run --generator=run-pod/v1 -it curl --image=radial/busyboxplus:curl
If you don't see a command prompt, try pressing enter.
[ root@curl:/ ]$ nslookup nginx
Server: 10.96.0.10
Address 1: 10.96.0.10 kube-dns.kube-system.svc.cluster.local

Name: nginx
Address 1: 10.108.192.221 nginx.default.svc.cluster.local

• ⾼可⽤

关机 master1，在⼀个随机 pod 中访问 Nginx 关机 master1，在⼀个随机 pod 中访问 Nginx

while true;do curl -I nginx && sleep 1 ;done

总结

• 关于版本

  • 内核版本 4.19 更加稳定此处不建议4.17（再新就是5了）

  • docker 最新稳定版是 1.17.12，此处是 1.18.06，虽 k8s 官⽅也确认兼容1.18.09 了但⽣产上还是建议 1.17.12

• 关于⽹络，各家选择不同，flannel在中⼩公司较为普遍，但部署前要选好⽹络插件，在配置⽂件中提前设置好（官⽅博客⼀开始的kubeadm配置中没写，后⾯在⽹络设置中⼜要求必须加）

• 出错处理

  • 想重置环境的话，kubeadm reset 是个很好的⼯具，但它并不会完全重置，在etcd 中的的部分数据（如 configmap secure 等)是没有被清空的，所以如果有必要重置真个环境，记得在 reset 后将 etcd 也重置。

  • 重置 etcd 办法为清空 etcd 节点 /var/lib/etcd，重启 docker 服务）

• 翻墙

  • 镜像：kubeadm 已⽀持⾃定义镜像前缀,kubeadm-config.yaml 中设置 imageRepository 即可

  • yum，可提前下载导⼊，也可以设置 http_proxy 来访问

  • init，签发证书和 init 时需要连接 google，也可以设置 http_proxy来访问。

• 更多

  • 证书、升级问题将在下⼀篇继续介绍。

参考：

• https://kubernetes.io/docs/setup/independent/setup-ha-etcd-with-kubeadm/

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