注：本文基于CentOS 7.4编写

背景

根据yaml文件创建rc后，查询pods状态时，一直显示ContainerCreating，

[root@CentOS-7-4 /home/k8s]# kubectl get pods
NAME                 READY     STATUS              RESTARTS   AGE
redis-master-5zn2z   0/1       ContainerCreating   0          13s

解决方案

查看这个pods的详细信息，

[root@CentOS-7-4 /home/k8s]# kubectl describe pod redis-master-5zn2z
Name:		redis-master-5zn2z
Namespace:	default
Node:		192.168.0.29/192.168.0.29
Start Time:	Wed, 16 Jan 2019 07:50:04 -0500
Labels:		name=redis-master
Status:		Pending
IP:		
Controllers:	ReplicationController/redis-master
Containers:
  master:
    Container ID:		
    Image:			kubeguide/redis-master
    Image ID:			
    Port:			6379/TCP
    State:			Waiting
      Reason:			ContainerCreating
    Ready:			False
    Restart Count:		0
    Volume Mounts:		<none>
    Environment Variables:	<none>
Conditions:
  Type		Status
  Initialized 	True 
  Ready 	False 
  PodScheduled 	True 
No volumes.
QoS Class:	BestEffort
Tolerations:	<none>
Events:
  FirstSeen	LastSeen	Count	From				SubObjectPath	TypeReason		Message
  ---------	--------	-----	----				-------------	--------	------		-------
  1m		1m		1	{default-scheduler }				Normal		Scheduled	Successfully assigned redis-master-5zn2z to 192.168.0.29
  1m		18s		4	{kubelet 192.168.0.29}			Warning		FailedSync	Error syncing pod, skipping: failed to "StartContainer" for "POD" with ImagePullBackOff: "Back-off pulling image \"registry.access.redhat.com/rhel7/pod-infrastructure:latest\""

  1m	6s	4	{kubelet 192.168.0.29}		Warning	FailedSync	Error syncing pod, skipping: failed to "StartContainer" for "POD" with ErrImagePull: "image pull failed for registry.access.redhat.com/rhel7/pod-infrastructure:latest, this may be because there are no credentials on this request.  details: (open /etc/docker/certs.d/registry.access.redhat.com/redhat-ca.crt: no such file or directory)"

可见，是缺少了/etc/docker/certs.d/registry.access.redhat.com/redhat-ca.crt文件，

[root@CentOS-7-4 /home/k8s]# ll /etc/docker/certs.d/registry.access.redhat.com/redhat-ca.crt
lrwxrwxrwx. 1 root root 27 May 16  2018 /etc/docker/certs.d/registry.access.redhat.com/redhat-ca.crt -> /etc/rhsm/ca/redhat-uep.pem
[root@CentOS-7-4 /home/k8s]# ll /etc/rhsm/ca/redhat-uep.pem
ls: cannot access /etc/rhsm/ca/redhat-uep.pem: No such file or directory

使用yum查询/etc/rhsm/ca/redhat-uep.pem是哪个rpm包提供的，

[root@CentOS-7-4 /home/k8s]# yum provides */redhat-uep.pem
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
 * base: mirrors.cn99.com
 * extras: mirrors.cn99.com
 * updates: mirrors.cn99.com
python-rhsm-certificates-1.19.10-1.el7_4.x86_64 : Certificates required to communicate with a
                                                : Red Hat Unified Entitlement Platform
Repo        : base
Matched from:
Filename    : /etc/rhsm/ca/redhat-uep.pem

因此，安装python-rhsm-certificates组件即可。

但事实并不如此。。。。

[root@CentOS-7-4 /home/k8s]# yum install python-rhsm-certificates -y
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
 * base: mirrors.cn99.com
 * extras: mirrors.cn99.com
 * updates: mirrors.cn99.com
Package python-rhsm-certificates is obsoleted by subscription-manager-rhsm-certificates, trying to install subscription-manager-rhsm-certificates-1.21.10-3.el7.centos.x86_64 instead

python-rhsm-certificates不再被允许安装，改而使用subscription-manager-rhsm-certificates。其实用哪个倒无所谓，但是新的这个组件没有提供/etc/rhsm/ca/redhat-uep.pem文件，所以还是会出现ContainerCreating的情况。

所以只能用以下方式安装，也就是直接下载python-rhsm-certificates，然后手动安装。

[root@CentOS-7-4 /home/k8s]# yumdownloader python-rhsm-certificates
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
 * base: mirrors.cn99.com
 * extras: mirrors.cn99.com
 * updates: mirrors.cn99.com
python-rhsm-certificates-1.19.10-1.el7_4.x86_64.rpm                   |  41 kB  00:00:00     
[root@CentOS-7-4 /home/k8s]# ls
.  ..  python-rhsm-certificates-1.19.10-1.el7_4.x86_64.rpm 
[root@CentOS-7-4 /home/k8s]# rpm -e subscription-manager-rhsm-certificates
[root@CentOS-7-4 /home/k8s]# rpm -ivh python-rhsm-certificates-1.19.10-1.el7_4.x86_64.rpm
Preparing...                          ################################# [100%]
Updating / installing...
   1:python-rhsm-certificates-1.19.10-################################# [100%]
[root@CentOS-7-4 /home/k8s]# ll /etc/rhsm/ca/redhat-uep.pem
-rw-r--r-- 1 root root 7732 Oct 19  2017 /etc/rhsm/ca/redhat-uep.pem

同时需要注意的是，其他所有结点也都要这样安装，因为每个结点都有可能需要运行这个pod。

都安装好后，稍等一会( 一分钟左右)再查看，就可以看到running状态的pod了。

[root@CentOS-7-4 /home/k8s]# kubectl get pods
NAME                 READY     STATUS    RESTARTS   AGE
redis-master-nslvc   1/1       Running   0          12h