解决k8s出现pod服务一直处于ContainerCreating状态的问题的过程
参考于：
https://blog.csdn.net/learner198461/article/details/78036854
https://liyang.pro/solve-k8s-pod-containercreating/
根据实际情况稍微做了修改和说明。
在创建Dashborad时，查看状态总是ContainerCreating
[root@MyCentos7 k8s]# kubectl get pod --namespace=kube-system
NAME READY STATUS RESTARTS AGE
kubernetes-dashboard-2094756401-kzhnx 0/1 ContainerCreating 0 10m
通过kubectl describe命令查看具体信息（或查看日志/var/log/message）
[root@MyCentos7 k8s]# kubectl describe pod kubernetes-dashboard-2094756401-kzhnx --namespace=kube-system Name: kubernetes-dashboard-2094756401-kzhnx Namespace: kube-system Node: mycentos7-1/192.168.126.131 Start Time: Tue, 05 Jun 2018 19:28:25 +0800 Labels: app=kubernetes-dashboard pod-template-hash=2094756401 Status: Pending IP: Controllers: ReplicaSet/kubernetes-dashboard-2094756401 Containers: kubernetes-dashboard: Container ID: Image: daocloud.io/megvii/kubernetes-dashboard-amd64:v1.8.0 Image ID: Port: 9090/TCP Args: --apiserver-host=http://192.168.126.130:8080 State: Waiting Reason: ContainerCreating Ready: False Restart Count: 0 Liveness: http-get http://:9090/ delay=30s timeout=30s period=10s #success=1 #failure=3 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 Type Reason Message --------- -------- ----- ---- ------------- -------- ------ ------- 11m 11m 1 {default-scheduler } Normal Scheduled Successfully assigned kubernetes-dashboard-2094756401-kzhnx to mycentos7-1 11m 49s 7 {kubelet mycentos7-1} Warning FailedSync Error syncing pod, skipping: failed to "StartContainer" for "POD" with ErrImagePull: "image pull failede: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)" 11m 11s 47 {kubelet mycentos7-1} Warning FailedSync Error syncing pod, skipping: failed to "StartContainer" for "POD" with ImagePullBackOff: "Back-off pulling image \"registry.access.redh
在工作节点（node）上执行
发现此时会pull一个镜像registry.access.redhat.com/rhel7/pod-infrastructure:latest，当我手动pull时，提示如下错误：
[root@MyCentos7 k8s]# docker pull registry.access.redhat.com/rhel7/pod-infrastructure:latest
Trying to pull repository registry.access.redhat.com/rhel7/pod-infrastructure ...
open /etc/docker/certs.d/registry.access.redhat.com/redhat-ca.crt: no such file or directory
通过提示的路径查找该文件，是个软连接，链接目标是/etc/rhsm，查看没有rhsm
[root@MyCentos7 ca]# cd /etc/docker/certs.d/registry.access.redhat.com/
[root@MyCentos7 registry.access.redhat.com]# ll
总用量 0
lrwxrwxrwx. 1 root root 27 5月 11 14:30 redhat-ca.crt -> /etc/rhsm/ca/redhat-uep.pem
[root@MyCentos7 ca]# cd /etc/rhsm
-bash: cd: /etc/rhsm: 没有那个文件或目录
安装rhsm（node上）：
yum install *rhsm*
已加载插件：fastestmirror, langpacks
Loading mirror speeds from cached hostfile
* base: mirror.lzu.edu.cn
* extras: mirror.lzu.edu.cn
* updates: ftp.sjtu.edu.cn
base | 3.6 kB 00:00:00
extras | 3.4 kB 00:00:00
updates | 3.4 kB 00:00:00
软件包 python-rhsm-1.19.10-1.el7_4.x86_64 被已安装的 subscription-manager-rhsm-1.20.11-1.el7.centos.x86_64 取代
软件包 subscription-manager-rhsm-1.20.11-1.el7.centos.x86_64 已安装并且是最新版本
软件包 python-rhsm-certificates-1.19.10-1.el7_4.x86_64 被已安装的 subscription-manager-rhsm-certificates-1.20.11-1.el7.centos.x86_64 取代
软件包 subscription-manager-rhsm-certificates-1.20.11-1.el7.centos.x86_64 已安装并且是最新版本
但是在/etc/rhsm/ca/目录下依旧没有证书文件，于是反复卸载与安装都不靠谱，后来发现大家所谓yum install *rhsm*其实安装的的是python-rhsm-1.19.10-1.el7_4.x86_64和python-rhsm-certificates-1.19.10-1.el7_4.x86_64，但是在实际安装过程中会有如下提示:
软件包 python-rhsm-1.19.10-1.el7_4.x86_64 被已安装的 subscription-manager-rhsm-1.20.11-1.el7.centos.x86_64 取代
软件包 subscription-manager-rhsm-1.20.11-1.el7.centos.x86_64 已安装并且是最新版本
软件包 python-rhsm-certificates-1.19.10-1.el7_4.x86_64 被已安装的 subscription-manager-rhsm-certificates-1.20.11-1.el7.centos.x86_64 取代
软件包 subscription-manager-rhsm-certificates-1.20.11-1.el7.centos.x86_64 已安装并且是最新版本
罪魁祸首在这里。原来我们想要安装的rpm包被取代了。而取代后的rpm包在安装完成后之创建了目录，并没有证书文件redhat-uep.pem。于是乎，手动下载以上两个包
wget ftp://ftp.icm.edu.pl/vol/rzm6/linux-scientificlinux/7.4/x86_64/os/Packages/python-rhsm-certificates-1.19.9-1.el7.x86_64.rpm
wget ftp://ftp.icm.edu.pl/vol/rzm6/linux-scientificlinux/7.4/x86_64/os/Packages/python-rhsm-1.19.9-1.el7.x86_64.rpm
注：在此处有时会报错，提示找不到这两个rpm文件，此时需要手动登录到此FTP进行下载，文件要稍等会才会加载出来，然后下载所需的这两个rpm（可能是网络原因，有时不稳定）
注意版本要匹配，卸载安装错的包
yum remove *rhsm*
然后执行安装命令
rpm -ivh *.rpm
rpm -ivh *.rpm
警告：python-rhsm-1.19.9-1.el7.x86_64.rpm: 头V4 DSA/SHA1 Signature, 密钥 ID 192a7d7d: NOKEY
准备中... ################################# [100%]
正在升级/安装...
1:python-rhsm-certificates-1.19.9-1################################# [ 50%]
2:python-rhsm-1.19.9-1.el7 ################################# [100%]
我在这一步有出错了
[root@neal registry.access.redhat.com]# rpm -ivh *.rpm
警告：python-rhsm-1.19.9-1.el7.x86_64.rpm: 头V4 DSA/SHA1 Signature, 密钥 ID 192a7d7d: NOKEY
错误：依赖检测失败：
python-rhsm <= 1.20.3-1 被 (已安裝) subscription-manager-rhsm-1.20.11-1.el7.centos.x86_64 取代
python-rhsm-certificates <= 1.20.3-1 被 (已安裝) subscription-manager-rhsm-certificates-1.20.11-1.el7.centos.x86_64 取代
此时跳到分割线之下，用分割线下面的文章的方法remove掉已经有的包，再重新用上面的命令安装。
接着验证手动pull镜像
docker pull registry.access.redhat.com/rhel7/pod-infrastructure:latest
Trying to pull repository registry.access.redhat.com/rhel7/pod-infrastructure ...
latest: Pulling from registry.access.redhat.com/rhel7/pod-infrastructure
26e5ed6899db: Pull complete
66dbe984a319: Pull complete
9138e7863e08: Pull complete
Digest: sha256:92d43c37297da3ab187fc2b9e9ebfb243c1110d446c783ae1b989088495db931
Status: Downloaded newer image for registry.access.redhat.com/rhel7/pod-infrastructure:latest
问题解决。
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在《kubernetes权威指南》入门的一个例子中，发现pod一直处于ContainerCreating的状态，用kubectl describe pod mysql的时候发现如下报错：
Events:
FirstSeen LastSeen Count From SubObjectPath Type Reason Message
--------- -------- ----- ---- ------------- -------- ------ -------
1h 24m 17 {kubelet 127.0.0.1} 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)"
1h 19m 291 {kubelet 127.0.0.1} 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\""
15m 15m 1 {kubelet 127.0.0.1} Warning MissingClusterDNS kubelet does not have ClusterDNS IP configured and cannot create Pod using "ClusterFirst" policy. Falling back to DNSDefault policy.
15m 15m 1 {kubelet 127.0.0.1} spec.containers{mysql} Normal Pulling pulling image "mysql"
7m 7m 1 {kubelet 127.0.0.1} Warning MissingClusterDNS kubelet does not have ClusterDNS IP configured and cannot create Pod using "ClusterFirst" policy. Falling back to DNSDefault policy.
7m 7m 1 {kubelet 127.0.0.1} spec.containers{mysql} Normal Pulling pulling image "mysql"
问题是比较明显的，就是没有/etc/docker/certs.d/registry.access.redhat.com/redhat-ca.crt文件，用ls -l查看之后发现是一个软链接，链接到/etc/rhsm/ca/redhat-uep.pem，但是这个文件不存在，使用yum search *rhsm*命令：
- 安装
python-rhsm-certificates包：
# yum install python-rhsm-certificates -y
这里又出现问题了:
python-rhsm-certificates <= 1.20.3-1 被 (已安裝) subscription-manager-rhsm-certificates-1.20.11-1.el7.centos.x86_64 取代
那么怎么办呢，我们直接卸载掉subscription-manager-rhsm-certificates包，使用yum remove subscription-manager-rhsm-certificates -y命令，然后下载python-rhsm-certificates包：
# wget http://mirror.centos.org/centos/7/os/x86_64/Packages/python-rhsm-certificates-1.19.10-1.el7_4.x86_64.rpm
然后手动安装该rpm包：
# rpm -ivh python-rhsm-certificates
这时发现/etc/rhsm/ca/redhat-uep.pem文件已存在。
- 使用
docker pull registry.access.redhat.com/rhel7/pod-infrastructure:latest命令下载镜像，但是可能会很慢，可以到https://dashboard.daocloud.io网站上注册账号，然后点击加速器，然后复制代码执行，之后重启docker就会进行加速，如果重启docker服务的时候无法启动，使用systemctl status docker:
# systemctl status docker
● docker.service - Docker Application Container Engine
Loaded: loaded (/usr/lib/systemd/system/docker.service; enabled; vendor preset: disabled)
Active: failed (Result: exit-code) since 一 2018-05-28 22:13:37 CST; 13s ago
Docs: http://docs.docker.com
Process: 79849 ExecStart=/usr/bin/dockerd-current --add-runtime docker-runc=/usr/libexec/docker/docker-runc-current --default-runtime=docker-runc --exec-opt native.cgroupdriver=systemd --userland-proxy-path=/usr/libexec/docker/docker-proxy-current --init-path=/usr/libexec/docker/docker-init-current --seccomp-profile=/etc/docker/seccomp.json $OPTIONS $DOCKER_STORAGE_OPTIONS $DOCKER_NETWORK_OPTIONS $ADD_REGISTRY $BLOCK_REGISTRY $INSECURE_REGISTRY $REGISTRIES (code=exited, status=1/FAILURE)
Main PID: 79849 (code=exited, status=1/FAILURE)
5月 28 22:13:37 kube.example.com systemd[1]: Starting Docker Application Container Engine...
5月 28 22:13:37 kube.example.com dockerd-current[79849]: unable to configure the Docker daemon with file /etc/docker/daemon.json: invalid character '}' loo...y string
5月 28 22:13:37 kube.example.com systemd[1]: docker.service: main process exited, code=exited, status=1/FAILURE
5月 28 22:13:37 kube.example.com systemd[1]: Failed to start Docker Application Container Engine.
5月 28 22:13:37 kube.example.com systemd[1]: Unit docker.service entered failed state.
5月 28 22:13:37 kube.example.com systemd[1]: docker.service failed.
Hint: Some lines were ellipsized, use -l to show in full
这时将/etc/docker/seccomp.json删除，再次重启即可
- 这时将之前创建的rc、svc和pod全部删除重新创建，过一会就会发现pod启动成功
原因猜想：根据报错信息，pod启动需要
registry.access.redhat.com/rhel7/pod-infrastructure:latest镜像，需要去红帽仓库里下载，但是没有证书，安装证书之后就可以了