简介：
Kubernetes作为Google开源的容器运行平台，受到了大家的热捧。搭建一套完整的kubernetes平台，也成为试用这套平台必须迈过的坎儿。kubernetes1.5版本以及之前，安装还是相对比较方便的，官方就有通过yum源在centos7安装kubernetes。但是在kubernetes1.6之后，安装就比较繁琐了，需要证书各种认证，对于刚接触kubernetes的人来说很不友好。
docker : kubernetes依赖的容器运行时
kubelet: kubernetes最核心的agent组件,每个节点都会启动一个,负责像pods及节点的生命周期等管理
kubectl: kubernetes的命令行控制工具,只可以在master上使用.
kubeadm: 用来bootstrap kubernetes. 初始化一个k8s集群.
架构说明：
两台主机：
18.16.202.35 master
18.16.202.36 slaver
系统配置:
1.1 关闭防火墙
systemctl stop firewalld
systemctl disable firewalld
1.2 禁用SELinux
setenforce 0
编辑文件/etc/selinux/config，将SELINUX修改为disabled，如下：
sed -i 's/SELINUX=permissive/SELINUX=disabled/' /etc/sysconfig/selinux
#SELINUX=disabled
1.3 关闭系统Swap
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。方法一,通过kubelet的启动参数–fail-swap-on=false更改这个限制。方法二,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。
#注释掉swap分区
[root@localhost /]# sed -i 's/.*swap.*/#&/' /etc/fstab
#/dev/mapper/centos-swap swap swap defaults 0 0
[root@localhost /]# free -m
total used free shared buff/cache available
Mem: 962 154 446 6 361 612
Swap: 0 0 0
1.4 安装docker
sudo yum install -y yum-utils device-mapper-persistent-data lvm2
sudo yum-config-manager --add-repo https://download.docker.com/linux/centos/docker-ce.repo
sudo yum makecache fast
sudo yum -y install docker-ce
systemctl enable docker.service
systemctl restart docker
我这里安装的是docker-ce 18.06
使用kubeadm部署Kubernetes:
2.1 安装kubeadm和kubelet
下面在各节点安装kubeadm和kubelet：
# 配置源
$ 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=1
repo_gpgcheck=1
gpgkey=https://mirrors.aliyun.com/kubernetes/yum/doc/yum-key.gpg https://mirrors.aliyun.com/kubernetes/yum/doc/rpm-package-key.gpg
EOF
# 安装
$ yum makecache fast
$ yum install -y kubelet kubeadm kubectl ipvsadm
配置：
# 配置转发相关参数，否则可能会出错
$ cat <<EOF > /etc/sysctl.d/k8s.conf
net.bridge.bridge-nf-call-ip6tables = 1
net.bridge.bridge-nf-call-iptables = 1
vm.swappiness=0
EOF
# 使配置生效
$ sysctl --system
# 如果net.bridge.bridge-nf-call-iptables报错，加载br_netfilter模块
$ modprobe br_netfilter
$ sysctl -p /etc/sysctl.d/k8s.conf
# 加载ipvs相关内核模块
# 如果重新开机，需要重新加载（可以写在 /etc/rc.local 中开机自动加载）
$ modprobe ip_vs
$ modprobe ip_vs_rr
$ modprobe ip_vs_wrr
$ modprobe ip_vs_sh
$ modprobe nf_conntrack_ipv4
# 查看是否加载成功
$ lsmod | grep ip_vs
配置启动kubelet（所有节点）
# 配置kubelet使用国内pause镜像
# 配置kubelet的cgroups
# 获取docker的cgroups
DOCKER_CGROUPS=$(docker info | grep 'Cgroup' | cut -d' ' -f3)
echo $DOCKER_CGROUPS
cat >/etc/sysconfig/kubelet<<EOF
KUBELET_EXTRA_ARGS="--cgroup-driver=$DOCKER_CGROUPS --pod-infra-container-image=registry.cn-hangzhou.aliyuncs.com/google_containers/pause-amd64:3.1"
EOF
# 启动
$ systemctl daemon-reload
$ systemctl enable kubelet && systemctl restart kubelet
在这里使用systemctl status kubelet，你会发现报错误信息；
10月 11 00:26:43 node1 systemd[1]: kubelet.service: main process exited, code=exited, status=255/n/a
10月 11 00:26:43 node1 systemd[1]: Unit kubelet.service entered failed state.
10月 11 00:26:43 node1 systemd[1]: kubelet.service failed.运行
journalctl -xefu kubelet命令查看systemd日志才发现，真正的错误是：unable to load client CA file /etc/kubernetes/pki/ca.crt: open /etc/kubernetes/pki/ca.crt: no such file or directory这个错误在运行
kubeadm init生成CA证书后会被自动解决，此处可先忽略。简单地说就是在
kubeadm init之前kubelet会不断重启。
2.2 配置master节点
直接使用命令：
kubeadm init \
--kubernetes-version=v1.12.0 \
--pod-network-cidr=10.244.0.0/16 \
--apiserver-advertise-address=192.168.61.11 \
--ignore-preflight-errors=Swap
或者使用kubeadm-master.config配置文件，在/etc/kubernetes/文件夹下面操作：
# 1.11 版本 centos 下使用 ipvs 模式会出问题
# 参考 https://github.com/kubernetes/kubernetes/issues/65461
# 生成配置文件
cat >/etc/kubernetes/kubeadm-master.config<<EOF
apiVersion: kubeadm.k8s.io/v1alpha2
kind: MasterConfiguration
kubernetesVersion: v1.12.0
imageRepository: registry.cn-hangzhou.aliyuncs.com/google_containers
api:
advertiseAddress: 18.16.202.35
controllerManagerExtraArgs:
node-monitor-grace-period: 10s
pod-eviction-timeout: 10s
networking:
podSubnet: 10.244.0.0/16
kubeProxy:
config:
mode: ipvs
# mode: iptables
EOF
# 提前拉取镜像
# 如果执行失败 可以多次执行
kubeadm config images pull --config /etc/kubernetes/kubeadm-master.config
# 初始化
kubeadm init --config /etc/kubernetes/kubeadm-master.config
# 或者
# kubeadm init --config /etc/kubernetes/kubeadm-master.config --ignore-preflight-errors=all
安装过程中遇到异常：
[preflight] Some fatal errors occurred:
[ERROR DirAvailable--var-lib-etcd]: /var/lib/etcd is not empty直接删除/var/lib/etcd文件夹
如果初始化过程出现问题，使用如下命令重置：
kubeadm reset
rm -rf /var/lib/cni/ $HOME/.kube/config
2.3 初始化master节点：
[root@localhost kubernetes]# kubeadm init --config kubeadm-master.config
[init] using Kubernetes version: v1.12.0
[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_sh:{} nf_conntrack_ipv4:{} ip_vs:{} ip_vs_rr:{} ip_vs_wrr:{}]
you can solve this problem with following methods:
1. Run 'modprobe -- ' to load missing kernel modules;
2. Provide the missing builtin kernel ipvs support
[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'
[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
[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 [localhost.localdomain localhost] and IPs [127.0.0.1 ::1]
[certificates] Generated etcd/peer certificate and key.
[certificates] etcd/peer serving cert is signed for DNS names [localhost.localdomain localhost] and IPs [18.16.202.35 127.0.0.1 ::1]
[certificates] Generated etcd/healthcheck-client certificate and key.
[certificates] Generated apiserver-etcd-client certificate and key.
[certificates] Generated ca certificate and key.
[certificates] Generated apiserver certificate and key.
[certificates] apiserver serving cert is signed for DNS names [localhost.localdomain kubernetes kubernetes.default kubernetes.default.svc kubernetes.default.svc.cluster.local] and IPs [10.96.0.1 18.16.202.35]
[certificates] Generated apiserver-kubelet-client certificate and key.
[certificates] valid certificates and keys now exist in "/etc/kubernetes/pki"
[certificates] Generated sa key and public key.
[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
[apiclient] All control plane components are healthy after 40.510372 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
[markmaster] Marking the node localhost.localdomain as master by adding the label "node-role.kubernetes.io/master=''"
[markmaster] Marking the node localhost.localdomain as master by adding the taints [node-role.kubernetes.io/master:NoSchedule]
[patchnode] Uploading the CRI Socket information "/var/run/dockershim.sock" to the Node API object "localhost.localdomain" as an annotation
[bootstraptoken] using token: xc9gpo.mmv1mmsjhq6tzhdc
[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 18.16.202.35:6443 --token ccxrk8.myui0xu4syp99gxu --discovery-token-ca-cert-hash sha256:e3c90ace969aa4d62143e7da6202f548662866dfe33c140095b020031bff2986
上面记录了完成的初始化输出的内容，根据输出的内容基本上可以看出手动初始化安装一个Kubernetes集群所需要的关键步骤。
其中有以下关键内容：
[kubelet]生成kubelet的配置文件”/var/lib/kubelet/config.yaml”[certificates]生成相关的各种证书[kubeconfig]生成相关的kubeconfig文件[bootstraptoken]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-
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 18.16.202.35:6443 --token ccxrk8.myui0xu4syp99gxu --discovery-token-ca-cert-hash sha256:e3c90ace969aa4d62143e7da6202f548662866dfe33c140095b020031bff2986
2.4 配置使用kubectl
如下操作在master节点操作
$ rm -rf $HOME/.kube
$ mkdir -p $HOME/.kube
$ sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
$ sudo chown $(id -u):$(id -g) $HOME/.kube/config
# 查看node节点
$ kubectl get nodes
NAME STATUS ROLES AGE VERSION
node1 NotReady master 6m19s v1.12.0
2.5 配置使用网络插件
如下操作在master节点操作
# 下载配置
$ cd ~ && mkdir flannel && cd flannel
$ wget https://raw.githubusercontent.com/coreos/flannel/v0.10.0/Documentation/kube-flannel.yml
修改配置文件kube-flannel.yml:
# 修改kube-flannel.yml中配置
# 此处的ip配置要与上面kubeadm的pod-network一致
net-conf.json: |
{
"Network": "10.244.0.0/16",
"Backend": {
"Type": "vxlan"
}
}
# 默认的镜像是quay.io/coreos/flannel:v0.10.0-amd64，如果你能pull下来就不用修改镜像地址，否则，修改yml中镜像地址为阿里镜像源
image: registry.cn-shanghai.aliyuncs.com/gcr-k8s/flannel:v0.10.0-amd64
# 如果Node有多个网卡的话，参考flannel issues 39701，
# https://github.com/kubernetes/kubernetes/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。容器无法通信的情况，需要将kube-flannel.yml下载到本地，
# flanneld启动参数加上--iface=<iface-name>
containers:
- name: kube-flannel
image: registry.cn-shanghai.aliyuncs.com/gcr-k8s/flannel:v0.10.0-amd64
command:
- /opt/bin/flanneld
args:
- --ip-masq
- --kube-subnet-mgr
- --iface=ens33
- --iface=eth0
⚠️⚠️⚠️--iface=ens33 的值，是你当前的网卡,或者可以指定多网卡
# 1.12版本的kubeadm额外给node1节点设置了一个污点(Taint)：node.kubernetes.io/not-ready:NoSchedule，
# 很容易理解，即如果节点还没有ready之前，是不接受调度的。可是如果Kubernetes的网络插件还没有部署的话，节点是不会进入ready状态的。
# 因此我们修改以下kube-flannel.yaml的内容，加入对node.kubernetes.io/not-ready:NoSchedule这个污点的容忍：
tolerations:
- key: node-role.kubernetes.io/master
operator: Exists
effect: NoSchedule
- key: node.kubernetes.io/not-ready
operator: Exists
effect: NoSchedule
启动：
# 启动
$ kubectl apply -f ~/flannel/kube-flannel.yml
# 查看
$ kubectl get pods --namespace kube-system
# kubectl get service
$ kubectl get svc --namespace kube-system
# 只有网络插件也安装配置完成之后，才能会显示为ready状态
# 设置master允许部署应用pod，参与工作负载，现在可以部署其他系统组件
# 如 dashboard, heapster, efk等
$ kubectl taint nodes --all node-role.kubernetes.io/master-
# 或者 kubectl taint nodes node1 node-role.kubernetes.io/master-
node/node1 untainted
# master不运行pod
# kubectl taint nodes node1 node-role.kubernetes.io/master=:NoSchedule
2.6 配置node节点加入集群
如下操作在所有node节点操作
# 此命令为初始化master成功后返回的结果
$ kubeadm join 18.16.202.35:6443 --token ccxrk8.myui0xu4syp99gxu --discovery-token-ca-cert-hash sha256:e3c90ace969aa4d62143e7da6202f548662866dfe33c140095b020031bff2986
异常信息：
[preflight] running pre-flight checks
[discovery] Trying to connect to API Server "18.16.202.35:6443"
[discovery] Created cluster-info discovery client, requesting info from "https://18.16.202.35:6443"
[discovery] Requesting info from "https://18.16.202.35:6443" again to validate TLS against the pinned public key
[discovery] Failed to request cluster info, will try again: [Get https://18.16.202.35:6443/api/v1/namespaces/kube-public/configmaps/cluster-info: x509: certificate has expired or is not yet valid]
[discovery] Failed to request cluster info, will try again: [Get https://18.16.202.35:6443/api/v1/namespaces/kube-public/configmaps/cluster-info: x509: certificate has expired or is not yet valid]这个问题我这边是因为服务器时间不对，调整以后就ok了。
查看pods:
[root@node1 flannel]# kubectl get pods -n kube-system
NAME READY STATUS RESTARTS AGE
coredns-6c66ffc55b-l76bq 1/1 Running 0 16m
coredns-6c66ffc55b-zlsvh 1/1 Running 0 16m
etcd-node1 1/1 Running 0 16m
kube-apiserver-node1 1/1 Running 0 16m
kube-controller-manager-node1 1/1 Running 0 15m
kube-flannel-ds-sr6tq 0/1 CrashLoopBackOff 6 7m12s
kube-flannel-ds-ttzhv 1/1 Running 0 9m24s
kube-proxy-nfbg2 1/1 Running 0 7m12s
kube-proxy-r4g7b 1/1 Running 0 16m
kube-scheduler-node1 1/1 Running 0 16m
查看异常pod信息：
[root@node1 flannel]# kubectl describe pods kube-flannel-ds-sr6tq -n kube-system
Name: kube-flannel-ds-sr6tq
Namespace: kube-system
Priority: 0
PriorityClassName: <none>
。。。。。
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal Pulling 12m kubelet, node2 pulling image "registry.cn-shanghai.aliyuncs.com/gcr-k8s/flannel:v0.10.0-amd64"
Normal Pulled 11m kubelet, node2 Successfully pulled image "registry.cn-shanghai.aliyuncs.com/gcr-k8s/flannel:v0.10.0-amd64"
Normal Created 11m kubelet, node2 Created container
Normal Started 11m kubelet, node2 Started container
Normal Created 11m (x4 over 11m) kubelet, node2 Created container
Normal Started 11m (x4 over 11m) kubelet, node2 Started container
Normal Pulled 10m (x5 over 11m) kubelet, node2 Container image "registry.cn-shanghai.aliyuncs.com/gcr-k8s/flannel:v0.10.0-amd64" already present on machine
Normal Scheduled 7m15s default-scheduler Successfully assigned kube-system/kube-flannel-ds-sr6tq to node2
Warning BackOff 7m6s (x23 over 11m) kubelet, node2 Back-off restarting failed container
遇到这种情况直接 删除异常pod:
[root@node1 flannel]# kubectl delete pod kube-flannel-ds-sr6tq -n kube-system
pod "kube-flannel-ds-sr6tq" deleted
[root@node1 flannel]# kubectl get pods -n kube-system
NAME READY STATUS RESTARTS AGE
coredns-6c66ffc55b-l76bq 1/1 Running 0 17m
coredns-6c66ffc55b-zlsvh 1/1 Running 0 17m
etcd-node1 1/1 Running 0 16m
kube-apiserver-node1 1/1 Running 0 16m
kube-controller-manager-node1 1/1 Running 0 16m
kube-flannel-ds-7lfrh 1/1 Running 1 6s
kube-flannel-ds-ttzhv 1/1 Running 0 10m
kube-proxy-nfbg2 1/1 Running 0 7m55s
kube-proxy-r4g7b 1/1 Running 0 17m
kube-scheduler-node1 1/1 Running 0 16m
查看节点：
[root@node1 flannel]# kubectl get nodes -n kube-system
NAME STATUS ROLES AGE VERSION
node1 Ready master 17m v1.12.1
node2 Ready <none> 8m14s v1.12.1
2.7 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/
参考：
https://www.cnblogs.com/liangDream/p/7358847.html
https://my.oschina.net/binges/blog/1615955?p=2&temp=1521445654544
https://blog.frognew.com/2018/10/kubeadm-install-kubernetes-1.12.html
https://www.jianshu.com/p/31bee0cecaf2
https://www.zybuluo.com/ncepuwanghui/note/953929
https://www.kubernetes.org.cn/4256.html
https://note.youdao.com/share/?id=31d9d5db79cc3ae27e72c029b09ac4ab&type=note#/
https://juejin.im/post/5b45d4185188251ac062f27c
https://www.jianshu.com/p/02dc13d2f651
https://blog.csdn.net/qq_34857250/article/details/82562514
https://www.cnblogs.com/ssss429170331/p/7685044.html
https://imroc.io/posts/kubernetes/install-kubernetes-1.9-on-centos7-with-kubeadm/