本文个人博客地址为：http://www.huweihuang.com/article/kubernetes/kubernetes-troubleshooting/
本文个人博客地址为：https://huweihuang.net/article/kubernetes/kubernetes-troubleshooting/
该命令可以显示Pod创建时的配置定义、状态等信息和最近的Event事件，事件信息可用于排错。例如当Pod状态为Pending，可通过查看Event事件确认原因，一般原因有几种：
没有可用的Node可调度开启了资源配额管理并且当前Pod的目标节点上恰好没有可用的资源正在下载镜像（镜像拉取耗时太久）或镜像下载失败。kubectl describe还可以查看其它k8s对象：NODE,RC,Service,Namespace,Secrets。
kubectl describe pod <PodName> --namespace=<NAMESPACE>
以下是容器的启动命令非阻塞式导致容器挂掉，被k8s频繁重启所产生的事件。
kubectl describe pod --namespace= Events: FirstSeen LastSeen Count From SubobjectPath Reason Message ───────── ──────── ───── ──── ───────────── ────── ─────── 7m 7m 1 {scheduler } Scheduled Successfully assigned yangsc-1-0-0-index0 to 10.8.216.19 7m 7m 1 {kubelet 10.8.216.19} containers{infra} Pulled Container image "gcr.io/kube-system/pause:0.8.0" already present on machine 7m 7m 1 {kubelet 10.8.216.19} containers{infra} Created Created with docker id 84f133c324d0 7m 7m 1 {kubelet 10.8.216.19} containers{infra} Started Started with docker id 84f133c324d0 7m 7m 1 {kubelet 10.8.216.19} containers{yangsc0} Started Started with docker id 3f9f82abb145 7m 7m 1 {kubelet 10.8.216.19} containers{yangsc0} Created Created with docker id 3f9f82abb145 7m 7m 1 {kubelet 10.8.216.19} containers{yangsc0} Created Created with docker id fb112e4002f4 7m 7m 1 {kubelet 10.8.216.19} containers{yangsc0} Started Started with docker id fb112e4002f4 6m 6m 1 {kubelet 10.8.216.19} containers{yangsc0} Created Created with docker id 613b119d4474 6m 6m 1 {kubelet 10.8.216.19} containers{yangsc0} Started Started with docker id 613b119d4474 6m 6m 1 {kubelet 10.8.216.19} containers{yangsc0} Created Created with docker id 25cb68d1fd3d 6m 6m 1 {kubelet 10.8.216.19} containers{yangsc0} Started Started with docker id 25cb68d1fd3d 5m 5m 1 {kubelet 10.8.216.19} containers{yangsc0} Started Started with docker id 7d9ee8610b28 5m 5m 1 {kubelet 10.8.216.19} containers{yangsc0} Created Created with docker id 7d9ee8610b28 3m 3m 1 {kubelet 10.8.216.19} containers{yangsc0} Started Started with docker id 88b9e8d582dd 3m 3m 1 {kubelet 10.8.216.19} containers{yangsc0} Created Created with docker id 88b9e8d582dd 7m 1m 7 {kubelet 10.8.216.19} containers{yangsc0} Pulling Pulling image "gcr.io/test/tcp-hello:1.0.0" 1m 1m 1 {kubelet 10.8.216.19} containers{yangsc0} Started Started with docker id 089abff050e7 1m 1m 1 {kubelet 10.8.216.19} containers{yangsc0} Created Created with docker id 089abff050e7 7m 1m 7 {kubelet 10.8.216.19} containers{yangsc0} Pulled Successfully pulled image "gcr.io/test/tcp-hello:1.0.0" 6m 7s 34 {kubelet 10.8.216.19} containers{yangsc0} Backoff Back-off restarting failed docker containerkubectl describe node 10.8.216.20
[root@FC-43745A-10 ~]# kubectl describe node 10.8.216.20 Name: 10.8.216.20 Labels: kubernetes.io/hostname=10.8.216.20,namespace/bcs-cc=true,namespace/myview=true CreationTimestamp: Mon, 17 Apr 2017 11:32:52 +0800 Phase: Conditions: Type Status LastHeartbeatTime LastTransitionTime Reason Message ──── ────── ───────────────── ────────────────── ────── ─────── Ready True Fri, 18 Aug 2017 09:38:33 +0800 Tue, 02 May 2017 17:40:58 +0800 KubeletReady kubelet is posting ready status OutOfDisk False Fri, 18 Aug 2017 09:38:33 +0800 Mon, 17 Apr 2017 11:31:27 +0800 KubeletHasSufficientDisk kubelet has sufficient disk space available Addresses: 10.8.216.20,10.8.216.20 Capacity: cpu: 32 memory: 67323039744 pods: 40 System Info: Machine ID: 723bafc7f6764022972b3eae1ce6b198 System UUID: 4C4C4544-0042-4210-8044-C3C04F595631 Boot ID: da01f2e3-987a-425a-9ca7-1caaec35d1e5 Kernel Version: 3.10.0-327.28.3.el7.x86_64 OS Image: CentOS Linux 7 (Core) Container Runtime Version: docker://1.13.1 Kubelet Version: v1.1.1-xxx-13.1+79c90c68bfb72f-dirty Kube-Proxy Version: v1.1.1-xxx-13.1+79c90c68bfb72f-dirty ExternalID: 10.8.216.20 Non-terminated Pods: (6 in total) Namespace Name CPU Requests CPU Limits Memory Requests Memory Limits ───────── ──── ──────────── ────────── ─────────────── ───────────── bcs-cc bcs-cc-api-0-0-1364-index0 1 (3%) 1 (3%) 4294967296 (6%) 4294967296 (6%) bcs-cc bcs-cc-api-0-0-1444-index0 1 (3%) 1 (3%) 4294967296 (6%) 4294967296 (6%) fw fw-demo2-0-0-1519-index0 1 (3%) 1 (3%) 4294967296 (6%) 4294967296 (6%) myview myview-api-0-0-1362-index0 1 (3%) 1 (3%) 4294967296 (6%) 4294967296 (6%) myview myview-api-0-0-1442-index0 1 (3%) 1 (3%) 4294967296 (6%) 4294967296 (6%) qa-ts-dna ts-dna-console3-0-0-1434-index0 1 (3%) 1 (3%) 4294967296 (6%) 4294967296 (6%) Allocated resources: (Total limits may be over 100%, i.e., overcommitted. More info: http://releases.k8s.io/HEAD/docs/user-guide/compute-resources.md) CPU Requests CPU Limits Memory Requests Memory Limits ──────────── ────────── ─────────────── ───────────── 6 (18%) 6 (18%) 25769803776 (38%) 25769803776 (38%) No events.kubectl describe rc mytest-1-0-0 --namespace=test
[root@FC-43745A-10 ~]# kubectl describe rc mytest-1-0-0 --namespace=test Name: mytest-1-0-0 Namespace: test Image(s): gcr.io/test/mywebcalculator:1.0.1 Selector: app=mytest,appVersion=1.0.0 Labels: app=mytest,appVersion=1.0.0,env=ts,zone=inner Replicas: 1 current / 1 desired Pods Status: 1 Running / 0 Waiting / 0 Succeeded / 0 Failed No volumes. Events: FirstSeen LastSeen Count From SubobjectPath Reason Message ───────── ──────── ───── ──── ───────────── ────── ─────── 20h 19h 9 {replication-controller } FailedCreate Error creating: Pod "mytest-1-0-0-index0" is forbidden: limited to 10 pods 20h 17h 7 {replication-controller } FailedCreate Error creating: pods "mytest-1-0-0-index0" already exists 20h 17h 4 {replication-controller } SuccessfulCreate Created pod: mytest-1-0-0-index0kubectl describe namespace test
[root@FC-43745A-10 ~]# kubectl describe namespace test Name: test Labels: <none> Status: Active Resource Quotas Resource Used Hard --- --- --- cpu 5 20 memory 1342177280 53687091200 persistentvolumeclaims 0 10 pods 4 10 replicationcontrollers 8 20 resourcequotas 1 1 secrets 3 10 services 8 20 No resource limits.kubectl describe service xxx-containers-1-1-0 --namespace=test
[root@FC-43745A-10 ~]# kubectl describe service xxx-containers-1-1-0 --namespace=test Name: xxx-containers-1-1-0 Namespace: test Labels: app=xxx-containers,appVersion=1.1.0,env=ts,zone=inner Selector: app=xxx-containers,appVersion=1.1.0 Type: ClusterIP IP: 10.254.46.42 Port: port-dna-tcp-35913 35913/TCP Endpoints: 10.0.92.17:35913 Port: port-l7-tcp-8080 8080/TCP Endpoints: 10.0.92.17:8080 Session Affinity: None No events.1、查看指定pod的日志
kubectl logs <pod_name>
kubectl logs -f <pod_name> #类似tail -f的方式查看
2、查看上一个pod的日志
kubectl logs -p <pod_name>
3、查看指定pod中指定容器的日志
kubectl logs <pod_name> -c <container_name>
4、kubectl logs的更多使用请参考kubectl logs --help
[root@node5 ~]# kubectl logs --help Print the logs for a container in a pod. If the pod has only one container, the container name is optional. Usage: kubectl logs [-f] [-p] POD [-c CONTAINER] [flags] Aliases: logs, log Examples: # Return snapshot logs from pod nginx with only one container $ kubectl logs nginx # Return snapshot of previous terminated ruby container logs from pod web-1 $ kubectl logs -p -c ruby web-1 # Begin streaming the logs of the ruby container in pod web-1 $ kubectl logs -f -c ruby web-1 # Display only the most recent 20 lines of output in pod nginx $ kubectl logs --tail=20 nginx # Show all logs from pod nginx written in the last hour $ kubectl logs --since=1h nginx5、docker logs
如果有Node机器（即宿主机）的登录权限，可以到出问题的pod所调度到的机器上，通过docker logs的命令查看对应容器的问题原因。
例如：
docker ps -a |grep <container>
docker logs <container_id>
[root@kube-master ~]# docker ps -a |grep redis ee7398bba500 docker.io/redis@sha256:bb47379e6e0101441dbb1fe585171521e4ee2ebe1ae23f663232f56ac41551de "docker-entrypoint.sh" About a minute ago Exited (1) About a minute ago k8s_kubernetes-log-tail-bigdatalog-testappkey_test-add-plugins-403621826-bskfz_test-7da2c1_a5412774-d43f-11e7-98c3-a2642aaa3458_6 5360d15344fb docker.io/redis@sha256:bb47379e6e0101441dbb1fe585171521e4ee2ebe1ae23f663232f56ac41551de "docker-entrypoint.sh" 7 minutes ago Up 7 minutes k8s_kubernetes-log-tail-testagent_test-add-plugins-403621826-bskfz_test-7da2c1_a5412774-d43f-11e7-98c3-a2642aaa3458_0 [root@kube-master ~]# [root@kube-master ~]# docker logs ee7398bba500 1:C 28 Nov 13:32:29.352 # oO0OoO0OoO0Oo Redis is starting oO0OoO0OoO0Oo 1:C 28 Nov 13:32:29.354 # Redis version=4.0.6, bits=64, commit=00000000, modified=0, pid=1, just started 1:C 28 Nov 13:32:29.354 # Warning: no config file specified, using the default config. In order to specify a config file use redis-server /path/to/redis.conf 1:M 28 Nov 13:32:29.355 # Creating Server TCP listening socket *:6379: bind: Address already in use
以上报错是因为端口冲突问题：bind: Address already in use
在Linux系统上systemd系统来管理kubernetes服务，并且journal系统会接管服务程序的输出日志，可以通过systemctl status <xxx>或journalctl -u <xxx> -f来查看kubernetes服务的日志。
其中kubernetes组件包括：
k8s组件 涉及日志内容 备注 kube-apiserver kube-controller-managerPod扩容相关或RC相关 kube-schedulerPod扩容相关或RC相关 kubeletPod生命周期相关：创建、停止等 etcd也可以通过指定日志存放目录来保存和查看日志
--logtostderr=false：不输出到stderr--log-dir=/var/log/kubernetes:日志的存放目录--alsologtostderr=false:设置为true表示日志输出到文件也输出到stderr--v=0:glog的日志级别--vmodule=gfs*=2,test*=4：glog基于模块的详细日志级别kubectl describe <pod_name> --namespace=<NAMESPACE>
查看该POD的事件。
正在下载镜像但拉取不下来（镜像拉取耗时太久）[一般都是该原因]没有可用的Node可调度开启了资源配额管理并且当前Pod的目标节点上恰好没有可用的资源解决方法：
查看该POD所在宿主机与镜像仓库之间的网络是否有问题，可以手动拉取镜像删除POD实例，让POD调度到别的宿主机上kubectl get pods中Pod状态一会running，一会不是，且RESTARTS次数不断增加。
一般原因为容器启动命令不是阻塞式命令，导致容器运行后马上退出。
非阻塞式命令：
本身CMD指定的命令就是非阻塞式命令将服务启动方式设置为后台运行解决方法：
1、将命令改为阻塞式命令（前台运行），例如：zkServer.sh start-foreground
2、java运行程序的启动脚本将 nohup xxx &的nobup和&去掉，例如：
nohup $JAVA_HOME/bin/java $JAVA_OPTS -cp $CLASSPATH com.cnc.open.processor.Main &
改为：
$JAVA_HOME/bin/java $JAVA_OPTS -cp $CLASSPATH com.cnc.open.processor.Main
文章参考《Kubernetes权威指南》
