經過千辛萬苦終於在本地搭建k8s環境後，昨天在除錯的時候有出現了pod卡在ContainerCreating狀態的問題。

這個問題的原因有幾種，我遇到的問題是拉去image失敗，如“image pull failed for gcr.io/google_containers/pause:2.0”。原來k8s預設從gcr.io/google_containers拉去映象，國內網路無法訪問。原來忘了連線VPN了…

問題是比較低階，其實主要是想跟大家分享下定位的方法。主要是通過“kubectl describe pod PodName”指令檢視pod發生的事件，從事件列表中可以查詢到錯誤資訊。

[email protected]
 
-ubuntu-trusty-64:~/work/k8s-foo$ kubectl run foo --image=hello-world

deployment "foo" created

[email protected]-ubuntu-trusty-64:~/work/k8s-foo$ kubectl get pods

NAME                        READY     STATUS              RESTARTS   AGE
foo-928603113-igh2x         0/1       ContainerCreating   0          4
 
m

[email protected]-ubuntu-trusty-64:~/work/k8s-foo$ kubectl describe pod foo

Name:       foo-928603113-igh2x
Namespace:  default
Node:       127.0.0.1/127.0.0.1
Start Time: Mon, 11 Apr 2016 15:11:49 +0000
Labels:     pod-template-hash=928603113,run=foo
Status:     Pending
IP:     
Controllers:    ReplicaSet/foo-
 
928603113
Containers:
  foo:
    Container ID:   
    Image:      hello-world
    Image ID:       
    Port:       
    QoS Tier:
      memory:       BestEffort
      cpu:      BestEffort
    State:      Waiting
      Reason:       ContainerCreating
    Ready:      False
    Restart Count:  0
    Environment Variables:
Conditions:
  Type      Status
  Ready     False 
Volumes:
  default-token-fbasq:
    Type:   Secret (a volume populated by a Secret)
    SecretName: default-token-fbasq
Events:
  FirstSeen LastSeen    Count   From            SubobjectPath   Type        Reason      Message
  --------- --------    -----   ----            -------------   --------    ------      -------
  7m        7m      1   {default-scheduler }            Normal      Scheduled   Successfully assigned foo-928603113-igh2x to 127.0.0.1
  4m        4m      1   {kubelet 127.0.0.1}         Warning     FailedSync  Error syncing pod, skipping: failed to "StartContainer" for "POD" with ErrImagePull: "image pull failed for gcr.io/google_containers/pause:2.0, this may be because there are no credentials on this request.  details: (API error (500): unable to ping registry endpoint https://gcr.io/v0/\nv2 ping attempt failed with error: Get https://gcr.io/v2/: dial tcp 74.125.203.82:443: i/o timeout\n v1 ping attempt failed with error: Get https://gcr.io/v1/_ping: dial tcp 74.125.203.82:443: i/o timeout\n)"

晚間嘗試啟動kube-dns時也遇到了類似的問題。檢視kube-dns Service時一切正常：

vagrant@vagrant-ubuntu-trusty-64:~/work/k8s-foo$ kubectl get services kube-dns --namespace=kube-system
NAME       CLUSTER-IP   EXTERNAL-IP   PORT(S)         AGE
kube-dns   10.0.0.10    <none>        53/UDP,53/TCP   56m

但啟動一個Service之後嘗試使用Service名稱解析dns卻失敗了。執行“kubectl get pods –namespace=kube-system”檢視發現kube-dns相關pod啟動失敗了。

再通過“kubectl describe”檢視相關pod的事件時發現原來kube-dns啟動時也需要下載新映象。果斷開啟VPN，再重啟叢集，over。