kubernetes的雾里探花(一)－－kubectl的使用

查看pods:

# 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：

# 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:

# kubectl delete pod kube-flannel-ds-sr6tq -n kube-system
pod "kube-flannel-ds-sr6tq" deleted

# 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：

# 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

创建一个包含nginx服务的pod并运行:

[root@master /]# kubectl run nginx-test --image=daocloud.io/library/nginx --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-test created

根据提示：上面的方式将要废弃，使用新方法创建如下

[root@master /]# kubectl run --generator=run-pod/v1 nginx-test1 --image=daocloud.io/library/nginx --port=80 --replicas=1
pod/nginx-test1 created

或者：

# /opt/kubernetes/bin/kubectl run nginx --image=nginx --replicas=3
# /opt/kubernetes/bin/kubectl expose deployment nginx --port=88 --target-port=80 --type=NodePort

查看创建的pod：

[root@master /]# kubectl get pods
NAME                          READY   STATUS    RESTARTS   AGE
nginx-test-7fd67d86fd-mbpck   1/1     Running   0          2m55s
nginx-test1                   1/1     Running   0          115s

查看创建的deployment:旧方式默认直接创建deployment,新方式是直接创建Pod

[root@master /]# kubectl get deployment
NAME         READY   UP-TO-DATE   AVAILABLE   AGE
nginx-test   1/1     1            1           3m31s

创建完成后查看详细信息，获取nginx所在pod的内部IP地址：

[root@master ~]# kubectl get pods -o wide
NAME                                     READY STATUS  RESTARTS AGE     IP             NODE     NOMINATED NODE   READINESS GATES
nginx-test-7fd67d86fd-mbpck  1/1     Running   0          5m45s   10.244.2.2   node2   <none>           <none>
nginx-test1                             1/1     Running   0          4m45s   10.244.1.2   node1   <none>           <none>

在kubernetes集群内任意节点访问该nginx服务：

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[root@master ~]# curl 10.244.1.2
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>

创建与管理service:
将pod创建完成后，访问该pod内的服务只能在集群内部通过pod的的地址去访问该服务；当该pod出现故障后，该pod的控制器会重新创建一个包括该服务的pod,此时访问该服务须要获取该服务所在的新的pod的地址去访问。对此，可以创建一个service，当新的pod的创建完成后，service会通过pod的label连接到该服务，只需通过service即可访问该服务。

#删除当前的pod:

[root@master ~]# kubectl delete pod nginx-test-7fd67d86fd-mbpck
pod "nginx-test-7fd67d86fd-mbpck" deleted

# 删除pod后，查看pod信息时发现有创建了一个新的pod
[root@master ~]# kubectl get pods -o wide
NAME                          READY   STATUS    RESTARTS   AGE   IP           NODE    NOMINATED NODE   READINESS GATES
nginx-test-7fd67d86fd-lq282   1/1     Running   0          10s   10.244.1.3   node1   <none>           <none>
nginx-test1                   1/1     Running   0          13m   10.244.1.2   node1   <none>           <none>

# 创建service,并将包含nginx-test的标签加入进来
service的创建是通过”kubectl expose”命令来创建。该命令的具体用法可以通过” kubectl expose --help”查看。Service创建完成后，通过service地址访问pod中的服务依然只能通过集群内部的地址去访问。
~]# kubectl expose deployment nginx-test --name=nginx --port=80 --target-port=80 --protocol=TCP
service/nginx exposed

查看创建的service

~]# kubectl get svc
NAME         TYPE        CLUSTER-IP       EXTERNAL-IP   PORT(S)   AGE
kubernetes   ClusterIP   10.96.0.1        <none>        443/TCP   13h
nginx        ClusterIP   10.110.225.133   <none>        80/TCP    2m49s

此时就可以直接通过service地址访问nginx，pod被删除重新创建后，依然可以通过service访问pod中的服务。

~]# curl 10.110.225.133 
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>

通过service的名称去访问该service下的pod中的服务Service被创建后，通过service的名称去访问该service下的pod中的服务，但前提是，需要配置dns地址为core dns服务的地址；新建的pod中的DNS的地址为都为core DNS的地址；可以新建一个pod客户端完成测试。

查看coredns的地址

~]# 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   14h

新建一个pod客户端

[root@master /]# kubectl run  --generator=run-pod/v1 dig --rm -it --image=docker.io/azukiapp/dig /bin/sh

查看pod中容器的dns地址

/ # cat /etc/resolv.conf 
nameserver 10.96.0.10

不同的service选择不同的pod是通过pod标签来管理的，pod标签是在创建pod时指定的，service管理的标签也是在创建service时指定的。一个service管理的标签及pod的标签都可以通过命令查看。

查看名称为nginx的service管理的标签以及其他信息

~]# kubectl describe svc nginx 
Name:              nginx
Namespace:         default
Labels:            run=nginx-test
Annotations:       <none># 
Selector:          run=nginx-test
Type:              ClusterIP
IP:                10.110.225.133
Port:              <unset>  80/TCP
TargetPort:        80/TCP
Endpoints:         10.244.2.3:80
Session Affinity:  None
Events:            <none>

查看pod的标签

 ~]# kubectl get pods --show-labels
NAME                            READY   STATUS    RESTARTS   AGE   LABELS
client                          1/1     Running   0          21m   run=client
nginx-test-5bbfddf46b-w56l5     1/1     Running   0          41m   pod-template-hash=5bbfddf46b,run=nginx-test

coredns服务对service名称的解析是实时的，在service被重新创建后或者修改service的ip地址后，依然可以通过service名称访问pod中的服务。
删除并重新创建一个名称为nginx的service

~]# kubectl delete svc nginx
service "nginx" deleted

~]# kubectl expose deployment nginx-test --name=nginx
service/nginx exposed

获取新创建的service的IP地址

~]# kubectl get svc
NAME         TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)   AGE
kubernetes   ClusterIP   10.96.0.1       <none>        443/TCP   14h
nginx        ClusterIP   10.98.192.150   <none>        80/TCP    9s

pod的扩展与缩减
Pod创建完成后，当服务的访问量过大时，可以对pod的进行扩展让pod中的服务处理更多的请求；当访问量减小时，可以缩减pod数量，以节约资源。 这些操作都可以在线完成，并不会影响现有的服务。

扩展pod数量

~]# kubectl scale --replicas=5 deployment nginx-test
deployment.extensions/nginx-test scaled

查看扩展后的pod

~]# kubectl get pods
NAME                            READY   STATUS    RESTARTS   AGE
client                          1/1     Running   0          59m
nginx-test-5bbfddf46b-6kw49     1/1     Running   0          44s
nginx-test-5bbfddf46b-k6jh7     1/1     Running   0          44s
nginx-test-5bbfddf46b-pswmp     1/1     Running   1          9m19s
nginx-test-5bbfddf46b-w56l5     1/1     Running   1          79m
nginx-test-5bbfddf46b-wwtwz     1/1     Running   0          44s

缩减pod的数量为2个

~]# kubectl scale --replicas=2 deployment nginx-test 
deployment.extensions/nginx-test scaled

服务的在线升级与回滚
在kubernetes服务中部署完服务后，对服务的升级可以在线完成，升级出问题后，也可以在线完成回滚。

查看pod的名称及pod详细信息

~]# kubectl get pods
NAME                            READY   STATUS    RESTARTS   AGE
nginx-test-5bbfddf46b-6kw49     1/1     Running   0          32m
……

查看pod详细信息

~]# kubectl describe pods nginx-test-5bbfddf46b-6kw49
Name:               nginx-test-5bbfddf46b-6kw49
Namespace:          default
Priority:           0
PriorityClassName:  <none>
Node:               node02.dayi123.com/192.168.16.172~]# kubectl describe pods nginx-test-5bbfddf46b-6kw49
Name:               nginx-test-5bbfddf46b-6kw49
Namespace:          default
Priority:           0
PriorityClassName:  <none>
Node:               node02.dayi123.com/192.168.16.172
Start Time:         Tue, 25 Dec 2018 15:59:35 +0800
Labels:             pod-template-hash=5bbfddf46b
                    run=nginx-test
Annotations:        <none>
Status:             Running
IP:                 10.244.2.8
Controlled By:      ReplicaSet/nginx-test-5bbfddf46b
Containers:
  nginx-test:
    Container ID:   docker://5537c32a16b1dea8104b32379f1174585e~]# kubectl describe pods nginx-test-5bbfddf46b-6kw49
Name:               nginx-test-5bbfddf46b-6kw49
Namespace:          default
Priority:           0
PriorityClassName:  <none>
Node:               node02.dayi123.com/192.168.16.172~]# kubectl describe pods nginx-test-5bbfddf46b-6kw49
Name:               nginx-test-5bbfddf46b-6kw49
Namespace:          default
Priority:           0
PriorityClassName:  <none>
Node:               node02.dayi123.com/192.168.16.172
Start Time:         Tue, 25 Dec 2018 15:59:35 +0800
Labels:             pod-template-hash=5bbfddf46b
                    run=nginx-test
Annotations:        <none>
Status:             Running
IP:                 10.244.2.8
Controlled By:      ReplicaSet/nginx-test-5bbfddf46b
Containers:
  nginx-test:
    Container ID:   docker://5537c32a16b1dea8104b32379f1174585e
……

为了验证更加明显，更新时将nginx替换为httpd服务

~]# kubectl set image deployment nginx-test nginx-test=httpd:2.4-alpine
deployment.extensions/nginx-test image updated

实时查看更新过程

~]# kubectl get deployment -w
NAME           READY   UP-TO-DATE   AVAILABLE   AGE
nginx-test     4/5     5            4           5h36m
nginx-test   3/5   5     3     5h37m
nginx-test   4/5   5     4     5h38m
nginx-test   5/5   5     5     5h38m
nginx-test   5/5   5     5     5h38m
nginx-test   4/5   5     4     5h38m
nginx-test   5/5   5     5     5h38m

更新完成后在客户端验证

/ # wget  -O - -q nginx
<html><body><h1>It works!</h1></body></html>

通过kubernetes节点验证

~]# curl 10.98.192.150
<html><body><h1>It works!</h1></body></html>

更新后回滚为原来的nginx

~]# kubectl rollout undo deployment nginx-test
deployment.extensions/nginx-test rolled back

实时查看回滚的进度

~]# kubectl get deployment -w                 
NAME           READY   UP-TO-DATE   AVAILABLE   AGE
nginx-test     4/5     5            4           5h48m
nginx-test   5/5   5     5     5h48m
nginx-test   5/5   5     5     5h48m
nginx-test   4/5   5     4     5h48m

回滚完成后验证

~]# curl 10.98.192.150
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>

让节点外部客户能够通过service访问pod中服务，创建好pod及service后，无论是通过pod地址及service地址在集群外部都无法访问pod中的服务；如果想要在集群外部访问pod中的服务，需要修改service的类型为NodePort，修改后会自动在ipvs中添加nat规则，此时就可以通过node节点地址访问pod中的服务。

编辑配置文件

~]# kubectl edit svc nginx
. . . . . .
spec:
  clusterIP: 10.98.192.150
  ports:
  - port: 80
    protocol: TCP
    targetPort: 80
  selector:
    run: nginx-test
  sessionAffinity: None
  type: NodePort

配置完成后查看node节点监听的端口

~]# netstat -lntp
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name    
tcp        0      0 127.0.0.1:10248         0.0.0.0:*               LISTEN      1703/kubelet        
tcp        0      0 127.0.0.1:10249         0.0.0.0:*               LISTEN      100485/kube-proxy   
tcp        0      0 127.0.0.1:41101         0.0.0.0:*               LISTEN      1703/kubelet        
tcp        0      0 0.0.0.0:22              0.0.0.0:*               LISTEN      849/sshd            
tcp        0      0 127.0.0.1:25            0.0.0.0:*               LISTEN      937/master          
tcp6       0      0 :::10250                :::*                    LISTEN      1703/kubelet        
tcp6       0      0 :::31438                :::*                    LISTEN      100485/kube-proxy   

修改完配置后，查看node节点监听的端口发现多了31438端口，在外部可以通过node节点的地址及该端口访问pod内的服务。