kubernetes快速应用入门

kubectl 就是 api server的客户端工具

创建一个nginx的pod

[root@master ~]# kubectl run nginx-deploy --image=nginx:1.14-alpine --port=80 --replicas=1
kubectl run --generator=deployment/apps.v1 is DEPRECATED and will be removed in a future version. Use kubectl run --generator=run-pod/v1 or kubectl create instead.
deployment.apps/nginx-deploy created

查看pod状态

[root@master ~]# kubectl get deployment
NAME READY UP-TO-DATE AVAILABLE AGE
nginx-deploy 1/1 1 1 54s

[root@master ~]# kubectl get pods
NAME READY STATUS RESTARTS AGE
nginx-deploy-55d8d67cf-xdxcj 1/1 Running 0 85s

[root@master ~]# kubectl get pods -o wide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
nginx-deploy-55d8d67cf-xdxcj 1/1 Running 0 2m4s 10.244.1.2 node1 <none> <none>

[root@node1 ~]# ifconfig
cni0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1450
　　inet 10.244.1.1 netmask 255.255.255.0 broadcast 0.0.0.0
　　inet6 fe80::ac25:6fff:fe19:4a09 prefixlen 64 scopeid 0x20<link>
　　ether ae:25:6f:19:4a:09 txqueuelen 1000 (Ethernet)
　　RX packets 1 bytes 28 (28.0 B)
　　RX errors 0 dropped 0 overruns 0 frame 0
　　TX packets 8 bytes 656 (656.0 B)
　　TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0

10.244.1.1这个网段是24位掩码，因此10.244.1都是网络地址，它是整个大网10.244.0.0/16位掩码的一个子网。这个子网专供node1上的pod使用。
node2上面的都是10.244.2.1开始。和node1不冲突。

[root@node2 ~]# curl 10.244.1.2
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>
　　body {
　　　　width: 35em;
　　　　margin: 0 auto;
　　　　font-family: Tahoma, Verdana, Arial, sans-serif;
　　}
</style>
</head>
<body>
<h1>Welcome to nginx!</h1>
<p>If you see this page, the nginx web server is successfully installed and
working. Further configuration is required.</p>

<p>For online documentation and support please refer to
<a href="http://nginx.org/">nginx.org</a>.<br/>
Commercial support is available at
<a href="http://nginx.com/">nginx.com</a>.</p>

<p><em>Thank you for using nginx.</em></p>
</body>
</html>

这时说明nginx的pod已经运行起来了。

这时的nginx只能被集群内部访问，还没法对外，所以需要创建service层来代理。

[root@master ~]# kubectl expose deployment nginx-deploy --name=nginx --port=80 --target-port=80 --protocol=TCP
service/nginx exposed

把deployment控制器相关的pod资源都创建为一个服务nginx-deploy，而服务名字叫nignx ，服务的端口号为80，pod的端口号，TCP服务。默认用的是Cluster-IP

[root@master ~]# kubectl get svc (svc是services的简写)
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 3d
nginx ClusterIP 10.96.69.143 <none> 80/TCP 3m24s

nginx的CLUSTER-IP是动态生成的，10.96.69.143是10.96.0.0/12位掩码中的地址。暴露的地址是80端口。

[root@master ~]# curl 10.96.69.143
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>
　　body {
　　　　width: 35em;
　　　　margin: 0 auto;
　　　　font-family: Tahoma, Verdana, Arial, sans-serif;
　　}
</style>
</head>
<body>
<h1>Welcome to nginx!</h1>
<p>If you see this page, the nginx web server is successfully installed and
working. Further configuration is required.</p>

<p>For online documentation and support please refer to
<a href="http://nginx.org/">nginx.org</a>.<br/>
Commercial support is available at
<a href="http://nginx.com/">nginx.com</a>.</p>

<p><em>Thank you for using nginx.</em></p>
</body>
</html>

这时候，访问service的地址就可以访问nginx了，依然在外部是访问不到的，因为创建service的时候用的是默认的CLUSTER-IP模式，是被集群内部pod客户端访问的。基于service自己的名称所访问的。

[root@master ~]# curl nginx
curl: (6) Could not resolve host: nginx; 未知的名称或服务

这时还是必须指定IP地址才能访问，因为还没有用DNS解析IP地址呢。所以需要去解析IP地址，这样以后直接访问ningx服务名就行了不用理IP地址。

查看DNS的地址：

[root@master ~]# kubectl get pods -n kube-system -o wide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
coredns-fb8b8dccf-8lczd 1/1 Running 1 3d 10.244.0.5 master <none> <none>
coredns-fb8b8dccf-rljmp 1/1 Running 1 3d 10.244.0.4 master <none> <none>
etcd-master 1/1 Running 3 3d 192.168.163.100 master <none> <none>
kube-apiserver-master 1/1 Running 4 3d 192.168.163.100 master <none> <none>
kube-controller-manager-master 1/1 Running 9 3d 192.168.163.100 master <none> <none>
kube-flannel-ds-amd64-26kk7 1/1 Running 1 26h 192.168.163.102 node2 <none> <none>
kube-flannel-ds-amd64-428x9 1/1 Running 1 26h 192.168.163.101 node1 <none> <none>
kube-flannel-ds-amd64-mj4s6 1/1 Running 1 28h 192.168.163.100 master <none> <none>
kube-proxy-5s2gz 1/1 Running 1 26h 192.168.163.101 node1 <none> <none>
kube-proxy-lwntd 1/1 Running 3 3d 192.168.163.100 master <none> <none>
kube-proxy-tjcpd 1/1 Running 1 26h 192.168.163.102 node2 <none> <none>
kube-scheduler-master 1/1 Running 8 3d 192.168.163.100 master <none> <none>

[root@master ~]# kubectl get svc -n kube-system
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
kube-dns ClusterIP 10.96.0.10 <none> 53/UDP,53/TCP,9153/TCP 3d

安装解析命令：

[root@master ~]# yum -y install bind-utils

创建一个临时的客户端进去设置DNS
[root@master ~]# kubectl run client1 --image=busybox --replicas=1 -it --restart=Never
If you don't see a command prompt, try pressing enter.
/ # cat /etc/resolv.conf
nameserver 10.96.0.10
search default.svc.cluster.local svc.cluster.local cluster.local
options ndots:5

default.svc.cluster.local 是一个特殊域名， 表示是你的kubenetes集群的本地pod资源特定后缀，而default表示这个pod所属的名称空间的名字，如果不给完整的名称，搜索的时候就搜索的域就不一样。

[root@master ~]# dig -t A nginx.default.svc.cluster.local @10.96.0.10

; <<>> DiG 9.9.4-RedHat-9.9.4-73.el7_6 <<>> -t A nginx.default.svc.cluster.local @10.96.0.10
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 18720
;; flags: qr aa rd; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1
;; WARNING: recursion requested but not available

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;nginx.default.svc.cluster.local. IN A

;; ANSWER SECTION:
nginx.default.svc.cluster.local. 5 IN A 10.96.69.143

;; Query time: 3 msec
;; SERVER: 10.96.0.10#53(10.96.0.10)
;; WHEN: 四 5月 16 10:05:59 CST 2019
;; MSG SIZE rcvd: 107

[root@master ~]# kubectl run client1 --image=busybox --replicas=1 -it --restart=Never
If you don't see a command prompt, try pressing enter.
/ # cat /etc/resolv.conf
nameserver 10.96.0.10
search default.svc.cluster.local svc.cluster.local cluster.local
options ndots:5
/ # nslookup nginx
Server: 10.96.0.10
Address: 10.96.0.10:53

Name: nginx.default.svc.cluster.local
Address: 10.96.69.143

*** Can't find nginx.svc.cluster.local: No answer
*** Can't find nginx.cluster.local: No answer
*** Can't find nginx.default.svc.cluster.local: No answer
*** Can't find nginx.svc.cluster.local: No answer
*** Can't find nginx.cluster.local: No answer

/ # wget nginx
Connecting to nginx (10.96.69.143:80)
index.html 100% |**********************************| 612 0:00:00 ETA
/ # wget -O - -q http://nginx:80/
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>
　　body {
　　　　width: 35em;
　　　　margin: 0 auto;
　　　　font-family: Tahoma, Verdana, Arial, sans-serif;
　　}
</style>
</head>
<body>
<h1>Welcome to nginx!</h1>
<p>If you see this page, the nginx web server is successfully installed and
working. Further configuration is required.</p>

<p>For online documentation and support please refer to
<a href="http://nginx.org/">nginx.org</a>.<br/>
Commercial support is available at
<a href="http://nginx.com/">nginx.com</a>.</p>

<p><em>Thank you for using nginx.</em></p>
</body>
</html>

这时已经解析成功，可以通过服务名ningx访问了。

为了测试是否成功，先删除pod试试看，看看在起来的pod是否能通过服务名访问。

[root@master ~]# kubectl get pods
NAME READY STATUS RESTARTS AGE
client1 1/1 Running 0 18m
nginx-deploy-55d8d67cf-xdxcj 1/1 Running 0 57m

[root@master ~]# kubectl delete pods nginx-deploy-55d8d67cf-xdxcj
pod "nginx-deploy-55d8d67cf-xdxcj" deleted

[root@master ~]# kubectl get pods
NAME READY STATUS RESTARTS AGE
client1 1/1 Running 0 19m
nginx-deploy-55d8d67cf-9rm67 0/1 ContainerCreating 0 22s

这时新的pod已经创建成功了。通过临时客户端在去访问服务名看看是否能联通。

/ # wget -O - -q http://nginx:80/
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>
　　body {
　　　　width: 35em;
　　　　margin: 0 auto;
　　　　font-family: Tahoma, Verdana, Arial, sans-serif;
　　}
</style>
</head>
<body>
<h1>Welcome to nginx!</h1>
<p>If you see this page, the nginx web server is successfully installed and
working. Further configuration is required.</p>

<p>For online documentation and support please refer to
<a href="http://nginx.org/">nginx.org</a>.<br/>
Commercial support is available at
<a href="http://nginx.com/">nginx.com</a>.</p>

<p><em>Thank you for using nginx.</em></p>
</body>
</html>

发现还是可以发现。没有问题。

[root@master ~]# kubectl get svc
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 3d
nginx ClusterIP 10.96.69.143 <none> 80/TCP 43m

[root@master ~]# kubectl describe svc nginx
Name:　　nginx
Namespace:　　default
Labels: 　　 run=nginx-deploy
Annotations:　　 <none>
Selector: 　　 run=nginx-deploy
Type: 　　 ClusterIP
IP: 　　 10.96.69.143
Port:　　 <unset> 80/TCP
TargetPort: 　　 80/TCP
Endpoints:　　 10.244.2.3:80
Session Affinity:　　 None
Events:　　 <none>

[root@master ~]# kubectl get pods --show-labels
NAME READY STATUS RESTARTS AGE LABELS
client1 1/1 Running 0 27m run=client1
nginx-deploy-55d8d67cf-9rm67 1/1 Running 0 8m18s pod-template-hash=55d8d67cf,run=nginx-deploy

可以得出结论是根据标签选中的，而不是根据IP地址选中的。

删除服务以后，在从新起个服务，发现客户端还是能直接发现nginx服务的。
[root@master ~]# kubectl get svc
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 3d1h
nginx ClusterIP 10.96.69.143 <none> 80/TCP 58m
[root@master ~]# kubectl delete svc nginx
service "nginx" deleted
[root@master ~]# kubectl get svc
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 3d1h
[root@master ~]# kubectl expose deployment nginx-deploy --name=nginx
service/nginx exposed
[root@master ~]# kubectl get svc
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 3d1h
nginx ClusterIP 10.104.156.118 <none> 80/TCP 7s

/ # wget -O - -q http://nginx:80/
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>
　　body {
　　　　width: 35em;
　　　　margin: 0 auto;
　　　　font-family: Tahoma, Verdana, Arial, sans-serif;
　　}
</style>
</head>
<body>
<h1>Welcome to nginx!</h1>
<p>If you see this page, the nginx web server is successfully installed and
working. Further configuration is required.</p>

<p>For online documentation and support please refer to
<a href="http://nginx.org/">nginx.org</a>.<br/>
Commercial support is available at
<a href="http://nginx.com/">nginx.com</a>.</p>

<p><em>Thank you for using nginx.</em></p>
</body>
</html>

只要服务在，就可以正确的反应到DNS上的。

查看控制器的详细信息：

[root@master ~]# kubectl describe deployment nginx-deploy
Name: 　　 nginx-deploy
Namespace:　　 default
CreationTimestamp:　　 Thu, 16 May 2019 08:41:11 +0800
Labels:　　 run=nginx-deploy
Annotations: 　　 deployment.kubernetes.io/revision: 1
Selector: 　　 run=nginx-deploy
Replicas: 　　 1 desired | 1 updated | 1 total | 1 available | 0 unavailable
StrategyType:　　 RollingUpdate
MinReadySeconds: 　　 0
RollingUpdateStrategy: 　　 25% max unavailable, 25% max surge
Pod Template:
  Labels: 　　 run=nginx-deploy
  Containers:
   nginx-deploy:
　Image: 　　 nginx:1.14-alpine
　Port:　　 80/TCP
　Host Port:　　 0/TCP
　Environment: 　　 <none>
　Mounts: 　　 <none>
  Volumes:　　 <none>
Conditions:
　Type Status Reason
　---- ------ ------
　Progressing True NewReplicaSetAvailable
　Available True MinimumReplicasAvailable
OldReplicaSets: <none>
NewReplicaSet: nginx-deploy-55d8d67cf (1/1 replicas created)
Events: <none

-w 表示监控进度

pod也是可以动态扩展的。当然也可以动态缩减，直接修改要改成的几，例如像缩减成3个。就把下面图片的改成 --replicas=3 就可以了

动态升级：

[root@master ~]# kubectl set image -h
Usage:
  kubectl set image (-f FILENAME | TYPE NAME) CONTAINER_NAME_1=CONTAINER_IMAGE_1
  ... CONTAINER_NAME_N=CONTAINER_IMAGE_N [options]

TYPE NAME 表示哪个pod
CONTAINER_NAME_1=CONTAINER_IMAGE_1 表示哪个容器替换成哪个镜像

比如像替换myapp-848b5b879b-gxxtc容器

通过kubectl describe pods 可以查看容器的各种信息，包括容器名字等等。

把v1版本升级成v2版本。第一个myapp是控制器的名字，第二个myapp是容器名

kubectl rollout status deployment myapp 可以查看更新的过程。

使用上面的命令在查看就可以看到是v2版本了。

也可以进行回滚操作：

kubectl rollout undo deployment myapp 回滚的时候可以指定回滚到哪个版本。不指定就默认回滚到上个版本。

如果想集群外部访问nginx的话，只需要修改service类型为NodeProt即可。

[root@master ~]# kubectl edit svc nginx
metadata:
  creationTimestamp: "2019-05-16T02:02:30Z"
  labels:
    run: nginx-deploy
  name: nginx
  namespace: default
  resourceVersion: "51839"
  selfLink: /api/v1/namespaces/default/services/nginx
  uid: a94b9787-777e-11e9-833b-000c29ac207f
spec:
  clusterIP: 10.104.156.118
  externalTrafficPolicy: Cluster
  ports:
  - nodePort: 31998
    port: 80
    protocol: TCP
    targetPort: 80
  selector:
    run: nginx-deploy
  sessionAffinity: None
  type: NodePort //这里修改成NodePort就可以外部访问了
status:
  loadBalancer: {}

[root@master ~]# kubectl get svc
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 3d2h
nginx NodePort 10.104.156.118 <none> 80:31998/TCP 67m

可以看到了多了一个端口。这个端口就是外部访问的端口

可以看到通过浏览器访问node2节点的IP地址和31998端口号就可以外部进行访问nginx了。