K8s - kubectl

work

Every time before start kubectl, remember export admin.config file first which contains server info for connection. The pwd should under path where the config file lies.

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$ export KUBECONFIG=./admin.conf

then start nodes

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$ kubectl get node

or

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$ kubectl get node -n testing

useful cmd

  1. 通过bash获得pod中某个容器的TTY，相当于登录容器

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    $ kubectl exec -it <pod-name> -c <container-name> -n <namespace> -- bash

    ref: kubectl 常用命令总结

  2. --
    shell命令前，要加– 号，不然shell命令中的参数，不能识别
    https://www.wandouip.com/t5i281271/

  3. 获取异常容器 (for debug)

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    $  kubectl get pods -n kube-system | grep -v Running

  4. get pod description (for debug)

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    $ kubectl describe pod <pod-name> -n <namespaces-name>

  5. 查看异常pod的日志 (for debug)

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    $ kubectl logs <pod-name> -n <namespaces-name>

  6. 查看相关的config map存不存在 (for debug)
    find the path to configmap file first

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    $ ls -l   # if the result is "total 0", means the configmap is not exist

  7. delete pod

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    $ kubectl delete pod <pod-name> -n <namespaces-name>

    -n <namespaces-name> can be omitted.

delete pods in batches (e.g. delete all evicted pods)

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$ kubectl get pods -A| grep Evicted | awk '{print $2}' | xargs kubectl delete pod -n cec
  1. create namespace
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    $ kubectl create namespace <name>
  2. check detailed info (especially for ip), add -o wide
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    $ kubectl get node -o wide -A
    NAME                  STATUS   ROLES    AGE     VERSION   INTERNAL-IP   EXTERNAL-IP   OS-IMAGE                KERNEL-VERSION               CONTAINER-RUNTIME
    pccc-303-7-master-1   Ready    master   3h12m   v1.18.2   192.168.2.1   <none>        CentOS Linux 7 (Core)   3.10.0-957.27.2.el7.x86_64   docker://19.3.5
    pccc-303-7-worker-1   Ready    worker   3h10m   v1.18.2   11.110.2.2    <none>        CentOS Linux 7 (Core)   3.10.0-957.27.2.el7.x86_64   docker://19.3.5
    pccc-303-7-worker-2   Ready    worker   3h10m   v1.18.2   11.110.2.3    <none>        CentOS Linux 7 (Core)   3.10.0-957.27.2.el7.x86_64   docker://19.3.5
    pccc-303-7-worker-3   Ready    worker   3h10m   v1.18.2   11.110.2.4    <none>        CentOS Linux 7 (Core)   3.10.0-957.27.2.el7.x86_64   docker://19.3.5
  3. watch -d: monitor all pods status with certain namespace:
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    $ watch -d kubectl get pods -n <namespace>
  4. Tail the system journal log
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    $ journalctl -f
  5. List config maps
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    $ kubectl get configmap -A
    # Check the configmap name for a specific namespace
    $ kubectl get cm -n <namespace>
    # Check the config in a configmap
    $ kubectl describe cm -n <namespace>
    # Edit a configmap
    $ kubectl edit configmap -n <namespace>
  6. List all services in a namespace, with extended info
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    $ kubectl get svc -n <namespace> -o json