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关于K8S：
Kubernetes是Google开源的容器集群管理系统。它构建于docker技术之上，为容器化的应用提供资源调度、部署运行、服务发现、扩 容缩容等整一套功能，本质上可看作是基于容器技术的mini-PaaS平台。
相信看过我博客的童鞋应该知道，我在14年的时候就发表了一篇名为Docker容器管理之Kubernetes当时国内Docker刚刚兴起，对于Docker的兴起我很有感触，仿佛一瞬间就火了，当时也是一个偶然的机会了解到K8S，所以当时就写文简单的介绍了下K8S以及如何采用源码部署。今时不同往日K8S在容器界已经是翘首，再读旧文有感而发，索性来研究下kubeadm安装K8S以及Dashboard功能预览。
环境描述：
采用CentOS7.4 minimual，docker 1.13，kubeadm 1.10.0，etcd 3.0， k8s 1.10.0
我们这里选用三个节点搭建一个实验环境。
10.0.100.202 k8smaster
10.0.100.203 k8snode1
10.0.100.204 k8snode2
准备环境：
1.配置好各节点hosts文件
2.关闭各节点系统防火墙
3.关闭各节点SElinux
4.关闭各节点swap
5.配置各节点系统内核参数使流过网桥的流量也进入iptables/netfilter框架中，在/etc/sysctl.conf中添加以下配置：
net.bridge.bridge-nf-call-iptables = 1
net.bridge.bridge-nf-call-ip6tables = 1
sysctl -p
使用kubeadm安装：
1.首先配置各节点阿里K8S YUM源
cat <<EOF > /etc/yum.repos.d/kubernetes.repo
[kubernetes]
name=Kubernetes
baseurl=https://mirrors.aliyun.com/kubernetes/yum/repos/kubernetes-el7-x86_64
enabled=1
gpgcheck=0
EOF
yum -y install epel-release
yum clean all
yum makecache
2.在各节点 安装kubeadm和相关工具包
yum -y install docker kubelet kubeadm kubectl kubernetes-cni
3. 启动Docker与kubelet服务
systemctl enable docker && systemctl start docker
systemctl enable kubelet && systemctl start kubelet
提示：此时kubelet的服务运行状态是异常的，因为缺少主配置文件kubelet.conf。但可以暂不处理，因为在完成Master节点的初始化后才会生成这个配置文件。
4.下载K8S相关镜像（Master节点操作）
因为无法直接访问gcr.io下载镜像，所以需要配置一个国内的容器镜像加速器
配置一个阿里云的加速器：
登录 https://cr.console.aliyun.com/
在页面中找到并点击镜像加速按钮，即可看到属于自己的专属加速链接，选择Centos版本后即可看到配置方法。
提示：在阿里云上使用 Docker 并配置阿里云镜像加速器，可能会遇到 daemon.json 导致 docker daemon 无法启动的问题，可以通过以下方法解决。
你需要的是编辑
vim /etc/sysconfig/docker
然后
OPTIONS='--selinux-enabled --log-driver=journald --registry-mirror=http://xxxx.mirror.aliyuncs.com'
registry-mirror 输入你的镜像地址
最后 service docker restart 重启 daemon
然后 ps aux | grep docker 然后你就会发现带有镜像的启动参数了。
5.下载K8S相关镜像
OK，解决完加速器的问题之后，开始下载k8s相关镜像，下载后将镜像名改为k8s.gcr.io/开头的名字，以便kubeadm识别使用。
#!/bin/bash
images=(kube-proxy-amd64:v1.10.0 kube-scheduler-amd64:v1.10.0 kube-controller-manager-amd64:v1.10.0 kube-apiserver-amd64:v1.10.0
etcd-amd64:3.1.12 pause-amd64:3.1 kubernetes-dashboard-amd64:v1.8.3 k8s-dns-sidecar-amd64:1.14.8 k8s-dns-kube-dns-amd64:1.14.8
k8s-dns-dnsmasq-nanny-amd64:1.14.8)
for imageName in ${images[@]} ; do
docker pull keveon/$imageName
docker tag keveon/$imageName k8s.gcr.io/$imageName
docker rmi keveon/$imageName
done
上面的shell脚本主要做了3件事，下载各种需要用到的容器镜像、重新打标记为符合k8s命令规范的版本名称、清除旧的容器镜像。
提示：镜像版本一定要和kubeadm安装的版本一致，否则会出现time out问题。
6.初始化安装K8S Master
执行上述shell脚本，等待下载完成后，执行kubeadm init
[root@k8smaster ~]# kubeadm init --kubernetes-version=v1.10.0 --pod-network-cidr=10.244.0.0/16
[init] Using Kubernetes version: v1.10.0
[init] Using Authorization modes: [Node RBAC]
Running pre-flight checks.
[WARNING Service-Kubelet]: kubelet service is not enabled, please run 'systemctl enable kubelet.service'
[WARNING FileExisting-crictl]: crictl not found in system path
Suggestion: go get github.com/kubernetes-incubator/cri-tools/cmd/crictl
Starting the kubelet service
[certificates] Generated ca certificate and key.
[certificates] Generated apiserver certificate and key.
[certificates] apiserver serving cert is signed for DNS names [k8smaster kubernetes kubernetes.default kubernetes.default.svc kubernetes.default.svc.cluster.local] and IPs [10.96.0.1 10.0.100.202]
[certificates] Generated apiserver-kubelet-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 [localhost] and IPs [127.0.0.1]
[certificates] Generated etcd/peer certificate and key.
[certificates] etcd/peer serving cert is signed for DNS names [k8smaster] and IPs [10.0.100.202]
[certificates] Generated etcd/healthcheck-client certificate and key.
[certificates] Generated apiserver-etcd-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: "/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"
[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 might take a minute or longer if the control plane images have to be pulled.
[url=] All control plane components are healthy after 21.001790 seconds
[uploadconfig] Storing the configuration used in ConfigMap "kubeadm-config" in the "kube-system" Namespace
[markmaster] Will mark node k8smaster as master by adding a label and a taint
[markmaster] Master k8smaster tainted and labelled with key/value: node-role.kubernetes.io/master=""
Using token: thczis.64adx0imeuhu23xv
Configured RBAC rules to allow Node Bootstrap tokens to post CSRs in order for nodes to get long term certificate credentials
Configured RBAC rules to allow the csrapprover controller automatically approve CSRs from a Node Bootstrap Token
Configured RBAC rules to allow certificate rotation for all node client certificates in the cluster
Creating the "cluster-info" ConfigMap in the "kube-public" namespace
[url=] Applied essential addon: kube-dns
[url=] 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 .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 10.0.100.202:6443 --token thczis.64adx0imeuhu23xv --discovery-token-ca-cert-hash sha256:fa7b11bb569493fd44554aab0afe55a4c051cccc492dbdfafae6efeb6ffa80e6
提示：选项--kubernetes-version=v1.10.0是必须的，否则会因为访问google网站被墙而无法执行命令。这里使用v1.10.0版本，刚才前面也说到了下载的容器镜像版本必须与K8S版本一致否则会出现time out。
上面的命令大约需要1分钟的过程，期间可以观察下tail -f /var/log/message日志文件的输出，掌握该配置过程和进度。上面最后一段的输出信息保存一份，后续添加工作节点还要用到。
7.配置kubectl认证信息（Master节点操作）
# 对于非root用户
mkdir -p $HOME/.kube
sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
sudo chown $(id -u):$(id -g) $HOME/.kube/config
# 对于root用户
export KUBECONFIG=/etc/kubernetes/admin.conf
也可以直接放到~/.bash_profile
echo "export KUBECONFIG=/etc/kubernetes/admin.conf" >> ~/.bash_profile
8.安装flannel网络（Master节点操作）
mkdir -p /etc/cni/net.d/
cat <<EOF> /etc/cni/net.d/10-flannel.conf
{
“name”: “cbr0”,
“type”: “flannel”,
“delegate”: {
“isDefaultGateway”: true
}
}
EOF
mkdir /usr/share/oci-umount/oci-umount.d -p
mkdir /run/flannel/
cat <<EOF> /run/flannel/subnet.env
FLANNEL_NETWORK=10.244.0.0/16
FLANNEL_SUBNET=10.244.1.0/24
FLANNEL_MTU=1450
FLANNEL_IPMASQ=true
EOF
kubectl apply -f https://raw.githubusercontent.com/coreos/flannel/v0.9.1/Documentation/kube-flannel.yml
9.让node1、node2加入集群
在node1和node2节点上分别执行 kubeadm join命令，加入集群：
[root@k8snode1 ~]# kubeadm join 10.0.100.202:6443 --token thczis.64adx0imeuhu23xv --discovery-token-ca-cert-hash sha256:fa7b11bb569493fd44554aab0afe55a4c051cccc492dbdfafae6efeb6ffa80e6
Running pre-flight checks.
[WARNING Service-Kubelet]: kubelet service is not enabled, please run 'systemctl enable kubelet.service'
[WARNING FileExisting-crictl]: crictl not found in system path
Suggestion: go get github.com/kubernetes-incubator/cri-tools/cmd/crictl
[discovery] Trying to connect to API Server "10.0.100.202:6443"
[discovery] Created cluster-info discovery client, requesting info from "https://10.0.100.202:6443"
[discovery] Requesting info from "https://10.0.100.202:6443" 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 "10.0.100.202:6443"
[discovery] Successfully established connection with API Server "10.0.100.202:6443"
This node has joined the cluster:
* Certificate signing request was sent to master 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.
提示：细心的童鞋应该会发现，这段命令其实就是前面K8S Matser安装成功后我让你们保存的那段命令。
默认情况下，Master节点不参与工作负载，但如果希望安装出一个All-In-One的k8s环境，则可以执行以下命令，让Master节点也成为一个Node节点：
kubectl taint nodes --all node-role.kubernetes.io/master-
10.验证K8S Master是否搭建成功（Master节点操作）
# 查看节点状态
kubectl get nodes
# 查看pods状态
kubectl get pods --all-namespaces
# 查看K8S集群状态
kubectl get cs
常见错误解析
安装时候最常见的就是time out，因为K8S镜像在国外，所以我们在前面就说到了提前把他下载下来，可以用一个国外机器采用habor搭建一个私有仓库把镜像都download下来。
[root@k8smaster ~]# kubeadm init
[init] Using Kubernetes version: v1.10.0
[init] Using Authorization modes: [Node RBAC]
Running pre-flight checks.
[WARNING Service-Kubelet]: kubelet service is not enabled, please run 'systemctl enable kubelet.service'
[WARNING FileExisting-crictl]: crictl not found in system path
Suggestion: go get github.com/kubernetes-incubator/cri-tools/cmd/crictl
Starting the kubelet service
[certificates] Generated ca certificate and key.
[certificates] Generated apiserver certificate and key.
[certificates] apiserver serving cert is signed for DNS names [k8smaster kubernetes kubernetes.default kubernetes.default.svc kubernetes.default.svc.cluster.local] and IPs [10.96.0.1 10.0.100.202]
[certificates] Generated apiserver-kubelet-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 [localhost] and IPs [127.0.0.1]
[certificates] Generated etcd/peer certificate and key.
[certificates] etcd/peer serving cert is signed for DNS names [k8smaster] and IPs [10.0.100.202]
[certificates] Generated etcd/healthcheck-client certificate and key.
[certificates] Generated apiserver-etcd-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: "/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"
[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 might take a minute or longer if the control plane images have to be pulled.
Unfortunately, an error has occurred:
timed out waiting for the condition
This error is likely caused by:
- The kubelet is not running
- The kubelet is unhealthy due to a misconfiguration of the node in some way (required cgroups disabled)
- Either there is no internet connection, or imagePullPolicy is set to "Never",
so the kubelet cannot pull or find the following control plane images:
- k8s.gcr.io/kube-apiserver-amd64:v1.10.0
- k8s.gcr.io/kube-controller-manager-amd64:v1.10.0
- k8s.gcr.io/kube-scheduler-amd64:v1.10.0
- k8s.gcr.io/etcd-amd64:3.1.12 (only if no external etcd endpoints are configured)
If you are on a systemd-powered system, you can try to troubleshoot the error with the following commands:
- 'systemctl status kubelet'
- 'journalctl -xeu kubelet'
couldn't initialize a Kubernetes cluster
那出现这个问题大部分原因是因为安装的K8S版本和依赖的K8S相关镜像版本不符导致的，关于这部分排错可以查看/var/log/message我们在文章开始安装的时候也提到了要多看日志。
还有些童鞋可能会说，那我安装失败了，怎么清理环境重新安装啊？下面教大家一条命令：
kubeadm reset
好了，至此就完成了K8S三节点集群的安装部署。
----------------------------
原文链接:https://blog.51cto.com/devingeng/2096495
程序猿的技术大观园：www.javathinker.net
[这个贴子最后由 flybird 在 2020-03-15 11:24:16 重新编辑]
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Java技术网站 → 『 Java开发技术 』 → 『 大数据处理和分布式架构专题 』 → 深入玩转K8S之使用kubeadm安装Kubernetes v1.10以及常见问题解答
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