base

Rancher基础

#使用glusterfs做存储，不懂glusterfs的请参考其他文章

Helm3

k8s-imagePullPolicy拉取策略

imagePullPolicy: Always 总是拉取 pull  以前好像是这个默认值
imagePullPolicy: IfNotPresent 默认值,本地有则使用本地镜像,不拉取
imagePullPolicy: Never 只使用本地镜像，从不拉取

k8s 进入pod shell


kubectl get pods   #查看所有正在运行的pod

NAME                            READY     STATUS    RESTARTS   AGE

nginx-56b8c64cb4-t97vb          1/1       Running   3          1d

 kubectl exec -it nginx-56b8c64cb4-t97vb -- /bin/bash      #假如当前pod只有一个容器,运行以下命令即可

root@nginx-56b8c64cb4-t97vb:/# ps -ef

UID        PID  PPID  C STIME TTY          TIME CMD

root         1     0  0 14:45 ?        00:00:00 nginx: master process nginx -g daemon off;

假如一个pod里有多个容器,用--container or -c 参数。例如:假如这里有个Pod名为my-pod,这个Pod有两个容器,分别名为main-app 和 helper-app,下面的命令将打开到main-app的shell的容器里。

kubectl exec -it my-pod --container main-app -- /bin/bash

k8s不进入pod，直接通过shell在pod里执行命令

k8s使用shell进入容器被拒绝连接

k8s删除pod

1、先删除pod2、再删除对应的deployment否则只是删除pod是不管用的，还会看到pod，因为deployment.yaml文件中定义了副本数量


实例如下：

删除pod

[root@test2 ~]# kubectl get pod -n jenkins
NAME                        READY     STATUS    RESTARTS   AGE
jenkins2-8698b5449c-grbdm   1/1       Running   0          8s
[root@test2 ~]# kubectl delete pod jenkins2-8698b5449c-grbdm -n jenkins
pod "jenkins2-8698b5449c-grbdm" deleted

查看pod仍然存储

[root@test2 ~]# kubectl get pod -n jenkins
NAME                        READY     STATUS    RESTARTS   AGE
jenkins2-8698b5449c-dbqqb   1/1       Running   0          8s
[root@test2 ~]# 

删除deployment

[root@test2 ~]# kubectl get deployment -n jenkins
NAME       DESIRED   CURRENT   UP-TO-DATE   AVAILABLE   AGE
jenkins2   1         1         1            1           17h
[root@test2 ~]# kubectl delete deployment jenkins2 -n jenkins

再次查看pod消失

deployment.extensions "jenkins2" deleted
[root@test2 ~]# kubectl get deployment -n jenkins
No resources found.
[root@test2 ~]# 
[root@test2 ~]# kubectl get pod -n jenkins
No resources found.

[ k8s中正确删除一个pod k8s中正确删除一个pod ]

coredns状态为ImagePullBackOff问题


kubectl get pods --all-namespaces

kube-system   coredns-7f6cbbb7b8-knhl8             0/1     ImagePullBackOff   0               24h
kube-system   coredns-7f6cbbb7b8-lt4k5             0/1     ImagePullBackOff   0               24h


解决办法：

确定pod所使用的镜像

kubectl get pods coredns-7f6cbbb7b8-knhl8 -n kube-system -o yaml | grep image




    image: registry.aliyuncs.com/google_containers/coredns:v1.8.4
    imagePullPolicy: IfNotPresent
  - image: registry.aliyuncs.com/google_containers/coredns:v1.8.4
    imageID: ""
        message: Back-off pulling image "registry.aliyuncs.com/google_containers/coredns:v1.8.4"

root@k8s-master:~# docker pull registry.aliyuncs.com/google_containers/coredns:v1.8.4
Error response from daemon: manifest for registry.aliyuncs.com/google_containers/coredns:v1.8.4 not found: manifest unknown: manifest unknown

拉个latest 再别名 
docker pull registry.aliyuncs.com/google_containers/coredns

root@k8s-master:~# docker  images | grep coredns 
registry.aliyuncs.com/google_containers/coredns                   latest    8d147537fb7d   3 months ago   47.6MB

强制 改一下 tag 
root@k8s-master:~# docker tag 8d147537fb7d  registry.aliyuncs.com/google_containers/coredns:v1.8.4

root@k8s-master:~# kubectl get pods --all-namespaces | grep coredns  
kube-system   coredns-7f6cbbb7b8-knhl8             1/1     Running            0                24h
kube-system   coredns-7f6cbbb7b8-lt4k5             1/1     Running            0                24h
root@k8s-master:~# 


root@k8s-master:~#  kubectl get all -n kube-system 
NAME                                     READY   STATUS             RESTARTS        AGE
pod/coredns-7f6cbbb7b8-knhl8             0/1     ImagePullBackOff   0               24h
pod/coredns-7f6cbbb7b8-lt4k5             0/1     ImagePullBackOff   0               24h

docker pull registry.aliyuncs.com/google_containers/coredns

coredns状态为ImagePullBackOff问题

k8s解决coredns 的ImagePullBackOff 和ErrImagePull 问题

https://stackoverflow.com/questions/53559291/kubernetes-coredns-in-crashloopbackoff

Kubernetes CoreDNS 状态是 CrashLoopBackOff 解决思路