k8s介绍
Kubernetes(k8s)是Google开源的容器集群管理系统（谷歌内部:Borg）。在Docker技术的基础上，为容器化的应用提供部署运行、资源调度、服务发现和动态伸缩等一系列完整功能，提高了大规模容器集群管理的便捷性。
Kubernetes优势:
– 容器编排
– 轻量级
– 开源
– 弹性伸缩
– 负载均衡
重要概念
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</pre>
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</pre>
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）
1.CPU数量至少两个否则会报错
2. 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
3.要保证打开内置的桥功能，这个是借助于iptables来实现的
需要安装docker才会成/proc/sys/net/bridge/bridge-nf-call-iptables
[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
[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</pre>
5.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：1.15.1
[root@ken ~]# kubeadm init --image-repository registry.aliyuncs.com/google_containers --kubernetes-version v1.15.1 --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（v1.15.1）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。
补充flannel网络介绍
Flannel是CoreOS团队针对Kubernetes设计的一个网络规划服务，简单来说，它的功能是让集群中的不同节点主机创建的Docker容器都具有全集群唯一的虚拟IP地址。
但在默认的Docker配置中，每个节点上的Docker服务会分别负责所在节点容器的IP分配。这样导致的一个问题是，不同节点上容器可能获得相同的内外IP地址。并使
这些容器之间能够之间通过IP地址相互找到，也就是相互ping通。
Flannel的设计目的就是为集群中的所有节点重新规划IP地址的使用规则，从而使得不同节点上的容器能够获得”同属一个内网”且”不重复的”IP地址，并让属于不同节
点上的容器能够直接通过内网IP通信。
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 v1.15.1 --apiserver-advertise-address 172.20.10.2 --pod-network-cidr=10.244.0.0/16
[init] Using Kubernetes version: v1.15.1
[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
[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
1.node节点关闭防火墙和selinux
2.禁用swap
3. 解析主机名
4.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
master节点上运行的服务
1.api-server
2.schedule
3.控制器管理器
4.etcd
5.pod网络–fannel
node节点上运行的服务
1.kubelet 是k8s集群当中唯一一个不是以容器运行的客户端
2.kube-proxy
3.pod
运行pod有两种方式
1.通过kubectl命令行工具进行创建
2.通过yml文件
查看所有的namespace
[root@ken1 ~]# kubectl get ns
NAME STATUS AGE
default Active 64m
kube-node-lease Active 64m
kube-public Active 64m
kube-system Active 64m
查看某个namespace运行了那些pod
[root@ken1 ~]# kubectl get po -n kube-system
NAME READY STATUS RESTARTS AGE
coredns-bccdc95cf-ggx7z 1/1 Running 0 63m
coredns-bccdc95cf-xxgjp 1/1 Running 0 63m
etcd-ken1 1/1 Running 0 62m
kube-apiserver-ken1 1/1 Running 0 62m
kube-controller-manager-ken1 1/1 Running 0 62m
kube-flannel-ds-amd64-6qmv4 1/1 Running 0 16m
kube-flannel-ds-amd64-p8rkl 1/1 Running 0 38m
kube-flannel-ds-amd64-vnt8c 1/1 Running 0 35m
kube-proxy-4gqq7 1/1 Running 0 35m
kube-proxy-5n2f4 1/1 Running 0 63m
kube-proxy-fr262 1/1 Running 0 16m
kube-scheduler-ken1 1/1 Running 0 62m
查看更加完整信息
[root@ken1 ~]# kubectl get po -n kube-system -o wide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
coredns-bccdc95cf-ggx7z 1/1 Running 0 67m 10.244.0.3 ken1 <none> <none>
coredns-bccdc95cf-xxgjp 1/1 Running 0 67m 10.244.0.2 ken1 <none> <none>
etcd-ken1 1/1 Running 0 66m 192.168.64.5 ken1 <none> <none>
kube-apiserver-ken1 1/1 Running 0 66m 192.168.64.5 ken1 <none> <none>
kube-controller-manager-ken1 1/1 Running 0 66m 192.168.64.5 ken1 <none> <none>
kube-flannel-ds-amd64-6qmv4 1/1 Running 0 20m 192.168.64.7 ken3 <none> <none>
kube-flannel-ds-amd64-p8rkl 1/1 Running 0 43m 192.168.64.5 ken1 <none> <none>
kube-flannel-ds-amd64-vnt8c 1/1 Running 0 40m 192.168.64.6 ken2 <none> <none>
kube-proxy-4gqq7 1/1 Running 0 40m 192.168.64.6 ken2 <none> <none>
kube-proxy-5n2f4 1/1 Running 0 67m 192.168.64.5 ken1 <none> <none>
kube-proxy-fr262 1/1 Running 0 20m 192.168.64.7 ken3 <none> <none>
kube-scheduler-ken1 1/1 Running 0 66m 192.168.64.5 ken1 <none> <none>
