centos7 部署 k8s 集群

1、环境准备

先准备一台centos7虚拟机

2、安装docker-ce

官方文档

# 卸载原来的docker
sudo yum remove docker \
                  docker-client \
                  docker-client-latest \
                  docker-common \
                  docker-latest \
                  docker-latest-logrotate \
                  docker-logrotate \
                  docker-engine

# 安装依赖
sudo yum update -y && sudo yum install -y yum-utils \
  device-mapper-persistent-data \
  lvm2
  
# 添加官方yum库
sudo yum-config-manager \
    --add-repo \
    https://download.docker.com/linux/centos/docker-ce.repo
    
# 安装docker
sudo yum install docker-ce docker-ce-cli containerd.io

# 安装指定版本docker
yum list docker-ce --showduplicates | sort -r
sudo yum install docker-ce-<VERSION_STRING> docker-ce-cli-<VERSION_STRING> containerd.io

# 查看docker版本
docker --version

# 开机启动
systemctl enable --now docker

或者使用脚本一键安装

curl -fsSL "https://get.docker.com/" | sh
systemctl enable --now docker

修改docker cgroup驱动，与k8s一致，使用systemd

# 修改docker cgroup驱动：native.cgroupdriver=systemd
cat > /etc/docker/daemon.json <<EOF
{
  "exec-opts": ["native.cgroupdriver=systemd"],
  "log-driver": "json-file",
  "log-opts": {
    "max-size": "100m"
  },
  "storage-driver": "overlay2",
  "storage-opts": [
    "overlay2.override_kernel_check=true"
  ]
}
EOF

systemctl restart docker  # 重启使配置生效

3、安装 kubelet kubeadm kubectl

官方文档

安装kubernetes的时候，需要安装kubelet, kubeadm等包，但k8s官网给的yum源是packages.cloud.google.com，国内访问不了，此时我们可以使用阿里云的yum仓库镜像。

cat <<EOF > /etc/yum.repos.d/kubernetes.repo
[kubernetes]
name=Kubernetes
baseurl=http://mirrors.aliyun.com/kubernetes/yum/repos/kubernetes-el7-x86_64
enabled=1
gpgcheck=0
repo_gpgcheck=0
gpgkey=http://mirrors.aliyun.com/kubernetes/yum/doc/yum-key.gpg
       http://mirrors.aliyun.com/kubernetes/yum/doc/rpm-package-key.gpg
EOF

# 关闭SElinux
setenforce 0
sed -i 's/^SELINUX=enforcing$/SELINUX=permissive/' /etc/selinux/config

# 安装kubelet kubeadm kubectl
yum install -y kubelet kubeadm kubectl --disableexcludes=kubernetes

systemctl enable --now kubelet  # 开机启动kubelet

# centos7用户还需要设置路由：
yum install -y bridge-utils.x86_64
modprobe  br_netfilter  # 加载br_netfilter模块，使用lsmod查看开启的模块
cat <<EOF >  /etc/sysctl.d/k8s.conf
net.bridge.bridge-nf-call-ip6tables = 1
net.bridge.bridge-nf-call-iptables = 1
EOF
sysctl --system  # 重新加载所有配置文件

systemctl disable --now firewalld  # 关闭防火墙

# k8s要求关闭swap  (qxl)
swapoff -a && sysctl -w vm.swappiness=0  # 关闭swap
sed -ri '/^[^#]*swap/s@^@#@' /etc/fstab  # 取消开机挂载swap

4、准备所需镜像

kubeadm config images pull # 拉取集群所需镜像，这个需要翻墙

# --- 不能翻墙可以尝试以下办法 ---
kubeadm config images list # 列出所需镜像

k8s.gcr.io/kube-apiserver:v1.15.3
k8s.gcr.io/kube-controller-manager:v1.15.3
k8s.gcr.io/kube-scheduler:v1.15.3
k8s.gcr.io/kube-proxy:v1.15.3
k8s.gcr.io/pause:3.1
k8s.gcr.io/etcd:3.3.10
k8s.gcr.io/coredns:1.3.1


# 根据所需镜像名字先拉取国内资源
docker pull mirrorgooglecontainers/kube-apiserver:v1.14.1
docker pull mirrorgooglecontainers/kube-controller-manager:v1.14.1
docker pull mirrorgooglecontainers/kube-scheduler:v1.14.1
docker pull mirrorgooglecontainers/kube-proxy:v1.14.1
docker pull mirrorgooglecontainers/pause:3.1
docker pull mirrorgooglecontainers/etcd:3.3.10
docker pull coredns/coredns:1.3.1  # 这个在mirrorgooglecontainers中没有

# 修改镜像tag
docker tag mirrorgooglecontainers/kube-apiserver:v1.14.1 k8s.gcr.io/kube-apiserver:v1.15.3
docker tag mirrorgooglecontainers/kube-controller-manager:v1.14.1 k8s.gcr.io/kube-controller-manager:v1.15.3
docker tag mirrorgooglecontainers/kube-scheduler:v1.14.1 k8s.gcr.io/kube-scheduler:v1.15.3
docker tag mirrorgooglecontainers/kube-proxy:v1.14.1 k8s.gcr.io/kube-proxy:v1.15.3
docker tag mirrorgooglecontainers/pause:3.1 k8s.gcr.io/pause:3.1
docker tag mirrorgooglecontainers/etcd:3.3.10 k8s.gcr.io/etcd:3.3.10
docker tag coredns/coredns:1.3.1 k8s.gcr.io/coredns:1.3.1

# 删除原来的镜像
docker rmi mirrorgooglecontainers/kube-apiserver:v1.14.1
docker rmi mirrorgooglecontainers/kube-controller-manager:v1.14.1
docker rmi mirrorgooglecontainers/kube-scheduler:v1.14.1
docker rmi mirrorgooglecontainers/kube-proxy:v1.14.1
docker rmi mirrorgooglecontainers/pause:3.1
docker rmi mirrorgooglecontainers/etcd:3.3.10
docker rmi coredns/coredns:1.3.1

使用虚拟机的可以做完以上步骤后，使用Vbox进行克隆。，一台做Master，另一台做Node
修改hostname

vim /etc/hostname
systemctl restart systemd-hostnamed

5、使用kubeadm创建集群

# 初始化Master（Master需要至少2核）此处会各种报错,异常...成功与否就在此
kubeadm init --pod-network-cidr=10.244.0.0/16 --kubernetes-version=v1.15.3 --apiserver-advertise-address=192.168.83.881.14.1
# --apiserver-advertise-address Master节点IP
# --pod-network-cidr 指定pod网络子网，使用fannel网络必须使用这个CIDR

# 初始化结果：
[init] Using Kubernetes version: v1.14.1
[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] Using existing etcd/ca certificate authority
[certs] Using existing etcd/server certificate and key on disk
[certs] Using existing etcd/peer certificate and key on disk
[certs] Using existing etcd/healthcheck-client certificate and key on disk
[certs] Using existing apiserver-etcd-client certificate and key on disk
[certs] Using existing ca certificate authority
[certs] Using existing apiserver certificate and key on disk
[certs] Using existing apiserver-kubelet-client certificate and key on disk
[certs] Using existing front-proxy-ca certificate authority
[certs] Using existing front-proxy-client certificate and key on disk
[certs] Using the existing "sa" 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
[apiclient] All control plane components are healthy after 21.503375 seconds
[upload-config] storing the configuration used in ConfigMap "kubeadm-config" in the "kube-system" Namespace
[kubelet] Creating a ConfigMap "kubelet-config-1.14" in namespace kube-system with the configuration for the kubelets in the cluster
[upload-certs] Skipping phase. Please see --experimental-upload-certs
[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: w2i0mh.5fxxz8vk5k8db0wq
[bootstrap-token] Configuring bootstrap tokens, cluster-info ConfigMap, RBAC Roles
[bootstrap-token] configured RBAC rules to allow Node Bootstrap tokens to post CSRs in order for nodes to get long term certificate credentials
[bootstrap-token] configured RBAC rules to allow the csrapprover controller automatically approve CSRs from a Node Bootstrap Token
[bootstrap-token] configured RBAC rules to allow certificate rotation for all node client certificates in the cluster
[bootstrap-token] creating the "cluster-info" ConfigMap in the "kube-public" namespace
[addons] Applied essential addon: CoreDNS
[addons] Applied essential addon: kube-proxy

Your Kubernetes control-plane 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/

Then you can join any number of worker nodes by running the following on each as root:

#每个机器创建的master以下部分都不同,需要自己保存好-qxl
kubeadm join 192.168.200.25:6443 --token our9a0.zl490imi6t81tn5u \
    --discovery-token-ca-cert-hash sha256:b93f710eb9b389a69f0cd0d6dcf7c82e389a68f009eb6b2028f69d54b099de16

普通用户设置权限

  # Master端：
  mkdir -p $HOME/.kube
  sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
  sudo chown $(id -u):$(id -g) $HOME/.kube/config
  # Node端：
  mkdir -p $HOME/.kube
  # 复制Master端配置文件$HOME/.kube/config到同级目录，否则后面kubectl get nodes会出现如下错误
  # The connection to the server localhost:8080 was refused - did you specify the right host or port?
  sudo chown $(id -u):$(id -g) $HOME/.kube/config

应用flannel网络

kubectl apply -f https://raw.githubusercontent.com/coreos/flannel/master/Documentation/kube-flannel.yml

node加入机器

# node1:
kubeadm join 192.168.200.25:6443 --token w2i0mh.5fxxz8vk5k8db0wq \
    --discovery-token-ca-cert-hash sha256:65e82e987f50908f3640df7e05c7a91f390a02726c9142808faa739d4dc24252 
# node2:
kubeadm join 192.168.200.25:6443 --token w2i0mh.5fxxz8vk5k8db0wq \
    --discovery-token-ca-cert-hash sha256:65e82e987f50908f3640df7e05c7a91f390a02726c9142808faa739d4dc24252

输出日志：

[preflight] Running pre-flight checks
[preflight] Reading configuration from the cluster...
[preflight] FYI: You can look at this config file with 'kubectl -n kube-system get cm kubeadm-config -oyaml'
[kubelet-start] Downloading configuration for the kubelet from the "kubelet-config-1.14" 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
[kubelet-start] Waiting for the kubelet to perform the TLS Bootstrap...

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 control-plane to see this node join the cluster.

# master：
kubectl get pods --all-namespaces
# ---输出信息---
NAMESPACE     NAME                             READY   STATUS    RESTARTS   AGE
kube-system   coredns-fb8b8dccf-rn8kd          1/1     Running   0          170m
kube-system   coredns-fb8b8dccf-slwr4          1/1     Running   0          170m
kube-system   etcd-master                      1/1     Running   0          169m
kube-system   kube-apiserver-master            1/1     Running   0          169m
kube-system   kube-controller-manager-master   1/1     Running   0          169m
kube-system   kube-flannel-ds-amd64-l8c7c      1/1     Running   0          130m
kube-system   kube-flannel-ds-amd64-lcmxw      1/1     Running   1          117m
kube-system   kube-flannel-ds-amd64-pqnln      1/1     Running   1          72m
kube-system   kube-proxy-4kcqb                 1/1     Running   0          170m
kube-system   kube-proxy-jcqjd                 1/1     Running   0          72m
kube-system   kube-proxy-vm9sj                 1/1     Running   0          117m
kube-system   kube-scheduler-master            1/1     Running   0          169m
# ---输出信息---


kubectl get nodes
# ---输出信息---
NAME     STATUS   ROLES    AGE    VERSION
master   Ready    master   171m   v1.14.1
node1    Ready    <none>   118m   v1.14.1
node2    Ready    <none>   74m    v1.14.1
# ---输出信息---

排错

journalctl -f  # 当前输出日志
journalctl -f -u kubelet  # 只看当前的kubelet进程日志

出于安全考虑，默认配置下Kubernetes不会将Pod调度到Master节点。如果希望将k8s-master也当作Node使用，可以执行如下命令：

kubectl describe node localhost
#输出:Taints:             node-role.kubernetes.io/master:NoSchedule(这个污点表示默认情况下master节点将不会调度运行Pod，即不运行工作负载。)
#可以部署到master
kubectl taint node k8s-master node-role.kubernetes.io/master=:NoSchedule-

其中k8s-master是主机节点hostname如果要恢复Master Only状态，执行如下命令：

#不会部署到master
kubectl taint node k8s-master node-role.kubernetes.io/master:NoSchedule

注意：kubeadm初始化的Kubernetes集群，master节点也被打上了一个node-role.kubernetes.io/master=的label，标识这个节点的角色为master。

给Node设置Label和设置污点是两个不同的操作。

实践：Kubernetes master节点不运行工作负载

Kubernetes集群的Master节点是十分重要的，一个高可用的Kubernetes集群一般会存在3个以上的master节点，为了保证master节点的稳定性，一般不推荐将业务的Pod调度到master节点上。 下面将介绍一下我们使用Kubernetes调度的Taints和和Tolerations特性确保Kubernetes的Master节点不执行工作负载的实践。

我们的Kubernetes集群中总共有3个master节点，节点的名称分别为k8s-01、k8s-02、k8s-03。 为了保证集群的稳定性，同时提高master节点的利用率，我们将其中一个节点设置为node-role.kubernetes.io/master:NoSchedule，另外两个节点设置为node-role.kubernetes.io/master:PreferNoSchedule，这样保证3个节点中的1个无论在任何情况下都将不运行业务Pod，而另外2个载集群资源充足的情况下尽量不运行业务Pod。

kubectl taint nodes k8s-01 node-role.kubernetes.io/master=:NoSchedule

kubectl taint nodes k8s-02 node-role.kubernetes.io/master=:PreferNoSchedule

kubectl taint nodes k8s-03 node-role.kubernetes.io/master=:PreferNoSchedule

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