k8s重要概念及部署k8s集群

1. cluster

cluster是计算、存储和网络资源的集合，k8s利用这些资源运行各种基于容器的应用。

2.master

master是cluster的大脑，他的主要职责是调度，即决定将应用放在那里运行。master运行linux操作系统，可以是物理机或者虚拟机。为了实现高可用，可以运行多个master。

3.node

node的职责是运行容器应用。node由master管理，node负责监控并汇报容器的状态，同时根据master的要求管理容器的生命周期。node运行在linux的操作系统上，可以是物理机或者是虚拟机。

4.pod

pod是k8s的最小工作单元。每个pod包含一个或者多个容器。pod中的容器会作为一个整体被master调度到一个node上运行。

5.controller

k8s通常不会直接创建pod,而是通过controller来管理pod的。controller中定义了pod的部署特性，比如有几个剧本，在什么样的node上运行等。为了满足不同的业务场景，k8s提供了多种controller，包括deployment、replicaset、daemonset、statefulset、job等。

6.deployment

是最常用的controller。deployment可以管理pod的多个副本，并确保pod按照期望的状态运行。

7.replicaset

实现了pod的多副本管理。使用deployment时会自动创建replicaset，也就是说deployment是通过replicaset来管理pod的多个副本的，我们通常不需要直接使用replicaset。

8.daemonset

用于每个node最多只运行一个pod副本的场景。正如其名称所示的，daemonset通常用于运行daemon。

9.statefuleset

能够保证pod的每个副本在整个生命周期中名称是不变的，而其他controller不提供这个功能。当某个pod发生故障需要删除并重新启动时，pod的名称会发生变化，同时statefulset会保证副本按照固定的顺序启动、更新或者删除。、

10.job

用于运行结束就删除的应用，而其他controller中的pod通常是长期持续运行的。

11.service

deployment可以部署多个副本，每个pod 都有自己的IP，外界如何访问这些副本那？答案是service。k8s的 service定义了外界访问一组特定pod的方式。service有自己的IP和端口，service为pod提供了负载均衡。k8s运行容器pod与访问容器这两项任务分别由controller和service执行。

12.namespace

可以将一个物理的cluster逻辑上划分成多个虚拟cluster，每个cluster就是一个namespace。不同的namespace里的资源是完全隔离的。

安装 kubelet、kubeadm 和 kubectl

master: 172.20.10.2

node1: 172.20.10.7

node2: 172.20.10.9

官方安装文档可以参考 https://kubernetes.io/docs/setup/independent/install-kubeadm/

第一步：安装docker

所有节点都需要安装docker，每个节点都需要使docker开机自启。

[root@localhost yum.repos.d]# wget http://mirrors.aliyun.com/docker-ce/linux/centos/docker-ce.repo
[root@ken ~]# yum install docker-ce -y
[root@ken ~]# mkdir /etc/docker
[root@ken ~]# cat /etc/docker/daemon.json
{
  "registry-mirrors": ["https://XXX.mirror.aliyuncs.com"]
}
[root@ken ~]# systemctl restart docker
[root@ken ~]# systemctl enable docker

第二步：配置k8s的yum文件

[k8s]
name=k8s
enabled=1
gpgcheck=0
baseurl=https://mirrors.aliyun.com/kubernetes/yum/repos/kubernetes-el7-x86_64/

第三步：安装 kubelet、kubeadm 和 kubectl（所有节点执行）

kubelet 运行在 Cluster 所有节点上，负责启动 Pod 和容器。

kubeadm 用于初始化 Cluster。

kubectl 是 Kubernetes 命令行工具。通过 kubectl 可以部署和管理应用，查看各种资源，创建、删除和更新各种组件。

[root@ken ~]# yum install kubelet kubeadm kubectl -y

第四步：启动kubelet

此时，还不能启动kubelet，因为此时配置还不能，现在仅仅可以设置开机自启动

[root@ken ~]# systemctl enable kubelet

用 kubeadm 创建 Cluster

第一步：环境准备（各个节点都需要执行下面的操作master,node）

CPU数量至少两个否则会报错
主机名必须解析

[root@ken ~]# cat /etc/hosts
127.0.0.1   localhost localhost.localdomain localhost4 localhost4.localdomain4
::1         localhost localhost.localdomain localhost6 localhost6.localdomain6
172.20.10.2 ken
172.20.10.7 host1
172.20.10.9 host2

要保证打开内置的桥功能，这个是借助于iptables来实现的

[root@ken ~]# echo "1" >/proc/sys/net/bridge/bridge-nf-call-iptables

需要禁止各个节点启用swap，如果启用了swap，那么kubelet就无法启动

1-k8s概念及集群部署 - 图1

[root@ken ~]# swapoff -a && sysctl -w vm.swappiness=0
vm.swappiness = 0
[root@ken ~]# free -m
              total        used        free      shared  buff/cache   available
Mem:            991         151         365           7         475         674
Swap:             0           0           0

关闭防火墙和selinux

第二步：初始化master

1.13.1版本可能太老了，在初始化的时候可以选择更高的版本，例如：1.14.1

[root@ken ~]# kubeadm init --image-repository registry.aliyuncs.com/google_containers --kubernetes-version v1.13.1 --apiserver-advertise-address 172.20.10.2 --pod-network-cidr=10.244.0.0/16

—image-repository string：这个用于指定从什么位置来拉取镜像（1.13版本才有的），默认值是k8s.gcr.io，我们将其指定为国内镜像地址：registry.aliyuncs.com/google_containers

—kubernetes-version string：指定kubenets版本号，默认值是stable-1，会导致从https://dl.k8s.io/release/stable-1.txt下载最新的版本号，我们可以将其指定为固定版本（最新版：v1.13.2）来跳过网络请求。

—apiserver-advertise-address 指明用 Master 的哪个 interface 与 Cluster 的其他节点通信。如果 Master 有多个 interface，建议明确指定，如果不指定，kubeadm 会自动选择有默认网关的 interface。

—pod-network-cidr指定 Pod 网络的范围。Kubernetes 支持多种网络方案，而且不同网络方案对 —pod-network-cidr有自己的要求，这里设置为10.244.0.0/16 是因为我们将使用 flannel 网络方案，必须设置成这个 CIDR。

看到下面的输出就表示你的集群创建成功了

[root@ken ~]# kubeadm init --image-repository registry.aliyuncs.com/google_containers --kubernetes-version v1.13.1 --apiserver-advertise-address 172.20.10.2 --pod-network-cidr=10.244.0.0/16
[init] Using Kubernetes version: v1.13.1
[preflight] Running pre-flight checks
    [WARNING SystemVerification]: this Docker version is not on the list of validated versions: 18.09.0. Latest validated version: 18.06
[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 "etcd/ca" certificate and key
[certs] Generating "etcd/server" certificate and key
[certs] etcd/server serving cert is signed for DNS names [ken localhost] and IPs [172.20.10.2 127.0.0.1 ::1]
[certs] Generating "etcd/peer" certificate and key
[certs] etcd/peer serving cert is signed for DNS names [ken localhost] and IPs [172.20.10.2 127.0.0.1 ::1]
[certs] Generating "etcd/healthcheck-client" certificate and key
[certs] Generating "apiserver-etcd-client" certificate and key
[certs] Generating "front-proxy-ca" certificate and key
[certs] Generating "front-proxy-client" certificate and key
[certs] Generating "ca" certificate and key
[certs] Generating "apiserver" certificate and key
[certs] apiserver serving cert is signed for DNS names [ken kubernetes kubernetes.default kubernetes.default.svc kubernetes.default.svc.cluster.local] and IPs [10.96.0.1 172.20.10.2]
[certs] Generating "apiserver-kubelet-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
[apiclient] All control plane components are healthy after 26.507041 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 "ken" as an annotation
[mark-control-plane] Marking the node ken as control-plane by adding the label "node-role.kubernetes.io/master=''"
[mark-control-plane] Marking the node ken as control-plane by adding the taints [node-role.kubernetes.io/master:NoSchedule]
[bootstrap-token] Using token: rn816q.zj0crlasganmrzsr
[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 172.20.10.2:6443 --token rn816q.zj0crlasganmrzsr --discovery-token-ca-cert-hash sha256:e339e4dbf6bd1323c13e794760fff3cbeb7a3f6f42b71d4cb3cffdde72179903

如果初始化失败，请使用如下代码清除后重新初始化

kubeadm reset
ifconfig cni0 down
ip link delete cni0
ifconfig flannel.1 down
ip link delete flannel.1
rm -rf /var/lib/cni/
rm -rf /var/lib/etcd/*

docker初始化成功下载的镜像

[root@ken ~]# docker image ls
REPOSITORY                                                        TAG                 IMAGE ID            CREATED             SIZE
registry.aliyuncs.com/google_containers/kube-proxy                v1.13.1             fdb321fd30a0        6 weeks ago         80.2MB
registry.aliyuncs.com/google_containers/kube-controller-manager   v1.13.1             26e6f1db2a52        6 weeks ago         146MB
registry.aliyuncs.com/google_containers/kube-apiserver            v1.13.1             40a63db91ef8        6 weeks ago         181MB
registry.aliyuncs.com/google_containers/kube-scheduler            v1.13.1             ab81d7360408        6 weeks ago         79.6MB
tomcat                                                            latest              48dd385504b1        7 weeks ago         475MB
memcached                                                         latest              8230c836a4b3        2 months ago        62.2MB
registry.aliyuncs.com/google_containers/coredns                   1.2.6               f59dcacceff4        2 months ago        40MB
busybox                                                           latest              59788edf1f3e        3 months ago        1.15MB
registry.aliyuncs.com/google_containers/etcd                      3.2.24              3cab8e1b9802        4 months ago        220MB
registry.aliyuncs.com/google_containers/pause                     3.1                 da86e6ba6ca1        13 months ago       742kB

第三步：配置kubectl

kubectl 是管理 Kubernetes Cluster 的命令行工具，前面我们已经在所有的节点安装了 kubectl。Master 初始化完成后需要做一些配置工作，然后 kubectl 就能使用了。

[root@ken ~]# mkdir -p $HOME/.kube
[root@ken ~]# cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
[root@ken ~]# chown $(id -u):$(id -g) $HOME/.kube/config

为了使用更便捷，启用 kubectl 命令的自动补全功能。

[root@ken ~]# echo "source <(kubectl completion bash)" >> ~/.bashrc

现在kubectl可以使用了

[root@ken ~]# kubectl get cs
NAME                 STATUS    MESSAGE              ERROR
scheduler            Healthy   ok                   
controller-manager   Healthy   ok                   
etcd-0               Healthy   {"health": "true"}

第四步：安装pod网络

要让 Kubernetes Cluster 能够工作，必须安装 Pod 网络，否则 Pod 之间无法通信。

Kubernetes 支持多种网络方案，这里我们先使用 flannel，后面还会讨论 Canal。

[root@ken ~]# kubectl apply -f https://raw.githubusercontent.com/coreos/flannel/master/Documentation/kube-flannel.yml

每个节点启动kubelet

[root@ken ~]# systemctl restart kubelet

等镜像下载完成以后，看到node的状态是ready了

[root@ken ~]# kubectl get nodes
NAME   STATUS   ROLES    AGE   VERSION
ken    Ready    master   17m   v1.13.2

此时，就可以看到pod信息了

[root@ken ~]# kubectl get pods -n kube-system
NAME                          READY   STATUS    RESTARTS   AGE
coredns-78d4cf999f-dbxpc      1/1     Running   0          19m
coredns-78d4cf999f-q9vq2      1/1     Running   0          19m
etcd-ken                      1/1     Running   0          18m
kube-apiserver-ken            1/1     Running   0          18m
kube-controller-manager-ken   1/1     Running   0          18m
kube-flannel-ds-amd64-fd8mv   1/1     Running   0          3m26s
kube-proxy-gwmr2              1/1     Running   0          19m
kube-scheduler-ken            1/1     Running   0          18m

添加 k8s-node1 和 k8s-node2

第一步：环境准备

node节点关闭防火墙和selinux
禁用swap
解析主机名
启动内核功能

启动kubeket

只需要设置为开机自启动就可以了

[root@host1 ~]#  systemctl enable kubelet

第二步：添加nodes

这里的—token 来自前面kubeadm init输出提示，如果当时没有记录下来可以通过kubeadm token list 查看。

kubeadm join 172.20.10.2:6443 --token rn816q.zj0crlasganmrzsr --discovery-token-ca-cert-hash sha256:e339e4dbf6bd1323c13e794760fff3cbeb7a3f6f42b71d4cb3cffdde72179903

输出如下的信息

[root@host2 ~]# kubeadm join 172.20.10.2:6443 --token rn816q.zj0crlasganmrzsr --discovery-token-ca-cert-hash sha256:e339e4dbf6bd1323c13e794760fff3cbeb7a3f6f42b71d4cb3cffdde72179903
[preflight] Running pre-flight checks
    [WARNING SystemVerification]: this Docker version is not on the list of validated versions: 18.09.1. Latest validated version: 18.06
[discovery] Trying to connect to API Server "172.20.10.2:6443"
[discovery] Created cluster-info discovery client, requesting info from "https://172.20.10.2:6443"
[discovery] Requesting info from "https://172.20.10.2:6443" 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 "172.20.10.2:6443"
[discovery] Successfully established connection with API Server "172.20.10.2:6443"
[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 "host2" 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.

第三步：查看nodes

根据上面最后一行的输出信息提示查看nodes

[root@ken ~]# kubectl get nodes
NAME    STATUS     ROLES    AGE     VERSION
host1   NotReady   <none>   2m54s   v1.13.2
host2   NotReady   <none>   2m16s   v1.13.2
ken     Ready      master   38m     v1.13.2

这里其实需要等一会，这个node1节点才会变成Ready状态，因为node节点需要下载四个镜像flannel coredns kube-proxy pause

过了一会查看节点状态

[root@ken ~]# kubectl get nodes
NAME    STATUS   ROLES    AGE     VERSION
host1   Ready    <none>   4m15s   v1.13.2
host2   Ready    <none>   3m37s   v1.13.2
ken     Ready    master   39m     v1.13.2

补充：移除NODE节点的方法

第一步：先将节点设置为维护模式(host1是节点名称)

[root@ken ~]# kubectl drain host1 --delete-local-data --force --ignore-daemonsets
node/host1 cordoned
WARNING: Ignoring DaemonSet-managed pods: kube-flannel-ds-amd64-ssqcl, kube-proxy-7cnsr
node/host1 drained

第二步：然后删除节点

[root@ken ~]# kubectl delete node host1
node "host1" deleted

第三步：查看节点

发现host1节点已经被删除了

[root@ken ~]# kubectl get nodes
NAME    STATUS   ROLES    AGE   VERSION
host2   Ready    <none>   13m   v1.13.2
ken     Ready    master   49m   v1.13.2

如果这个时候再想添加进来这个node，需要执行两步操作

第一步：停掉kubelet(需要添加进来的节点操作)

[root@host1 ~]# systemctl stop kubelet

第二步：删除相关文件

[root@host1 ~]# rm -rf /etc/kubernetes/*

第三步：添加节点

[root@host1 ~]# kubeadm join 172.20.10.2:6443 --token rn816q.zj0crlasganmrzsr --discovery-token-ca-cert-hash sha256:e339e4dbf6bd1323c13e794760fff3cbeb7a3f6f42b71d4cb3cffdde72179903

第四步：查看节点

[root@ken ~]# kubectl get nodes
NAME    STATUS   ROLES    AGE   VERSION
host1   Ready    <none>   13s   v1.13.2
host2   Ready    <none>   17m   v1.13.2
ken     Ready    master   53m   v1.13.2

忘掉token再次添加进k8s集群

第一步：主节点执行命令

获取token

[root@ken-master ~]# kubeadm token list
TOKEN                     TTL       EXPIRES                     USAGES                   DESCRIPTION                                                EXTRA GROUPS
ojxdod.fb7tqipat46yp8ti   10h       2019-05-06T04:55:42+08:00   authentication,signing   The default bootstrap token generated by 'kubeadm init'.   system:bootstrappers:kubeadm:default-node-token

第二步：获取ca证书sha256编码hash值

[root@ken-master ~]# openssl x509 -pubkey -in /etc/kubernetes/pki/ca.crt | openssl rsa -pubin -outform der 2>/dev/null | openssl dgst -sha256 -hex | sed 's/^.* //'
2f8888cdb01191ff6dbca0edb02dbb21a14469028e4ff2598854a4544c5fa751

第三步：从节点执行如下的命令

[root@ken-node1 ~]# systemctl stop kubelet

第四步：删除相关文件

[root@ken-node1 ~]# rm -rf /etc/kubernetes/*

第五步：加入集群

指定主节点IP，端口是6443

在生成的证书前有sha256:

[root@ken-node1 ~]# kubeadm join 192.168.64.10:6443 --token ojxdod.fb7tqipat46yp8ti  --discovery-token-ca-cert-hash sha256:2f8888cdb01191ff6dbca0edb02dbb21a14469028e4ff2598854a4544c5fa751

1-k8s概念及集群部署