pod

• filter via --field-selector

  • list all Failed pods

  • filter via Node Name

  • filter via json

  • list pod details for failure pods

• sort via --sort-by

  • sorting pods by nodeName

  • sort pods by restartCount

  • sort by restart count

  • sort via start time

  • get the oldest pod

  • sort via created time

• run & create

  • pod

  • deploy

  • svc

• list

  • watch pods with timestamp

  • list pod status with timestamp

  • list pod with nodename

  • list all ready pods

  • list error status pods

  • list all pods statuses only

  • list running images

  • list running pods

  • list pods on nodes

  • list all containers

  • list container images by pod

  • get port enabled in pod

  • get podIP

  • get the first deploy name in namespace

  • get all deploy names

  • item.metadata.name

• output

  • -o name

  • --template

  • custom-columns

• management

  • execute in pod

  • restart po

• resource managemenet

  • resource management for pods and containers

  • assign cpu resources to containers and pods

  • managing kubernetes resource limits

• troubleshooting

  • debug svc

references:

• * Create static Pods

• * Pod Lifecycle

• Pods

• Field Selectors

• Kubernetes Daemonset: A Comprehensive Guide

• Kubernetes Pod Priority, PriorityClass, and Preemption Explained

[!NOTE|label:pod phase]

VALUE	DESCRIPTION
Pending	The Pod has been accepted by the Kubernetes cluster, but one or more of the containers has not been set up and made ready to run
Running	The Pod has been bound to a node, and all of the containers have been created
Succeeded	All containers in the Pod have terminated in success, and will not be restarted.
Failed	All containers in the Pod have terminated, and at least one container has terminated in failure
Unknown	For some reason the state of the Pod could not be obtained

filter via --field-selector

list all Failed pods

$ kubectl -n <namespace> get po \
    --field-selector status.phase=Failed

filter via Node Name

$ kubectl -n <namespace> get po \
    [-o wide] \
    --field-selector spec.nodeName=master-node01
NAME                              READY   STATUS    RESTARTS   AGE     IP            NODE            NOMINATED NODE   READINESS GATES
devops-jenkins-659f4c6d44-d2w76   1/1     Running   0          2d22h   **.***.*.**   master-node01   <none>           <none>

• filter all pods running in particular node

  $ kubectl --all-namespaces get po \
      [-o wide] \
      --field-selector spec.nodeName=<node_name>

• filter all pods running in particular node via --template

  $ kubectl -n <namespace> get po \
            --template '{{range .items}}{{if eq .spec.nodeName "<nodeName>"}}{{.metadata.name}}{{"\n"}}{{end}}}{{end}}'

• via api

  $ curl --cacert ca.crt \
         --cert apiserver.crt \
         --key apiserver.key \
         https://<server>:<port>/api/v1/namespaces/<namespace>/pods?fieldSelector=spec.nodeName%3Dsomenodename

filter via json

$ kubectl get po -o json |
          jq -r '.items | sort_by(.spec.nodeName)[] | [.spec.nodeName,.metadata.name] | @tsv'

list pod details for failure pods

$ ns='my-namespace'
$ kubectleyword='tester'
$ for p in $(kubectl -n ${ns} get po --field-selector status.phase=Failed -o=name | /bin/grep ${keyword}); do
    echo "--- ${p} --- ";
    kubectl -n ${ns} describe ${p} | grep -E 'Annotations|Status|Reason|Message';
done

sort via --sort-by

sorting pods by nodeName

$ kubectl -n <namespace> get po \
    -o wide \
    --sort-by="{.spec.nodeName}"

sort pods by restartCount

$ kubectl -n <namespace> get po --sort-by="{.status.containerStatuses[:1].restartCount}"

sort by restart count

$ kubectl -n <namespace> get pods --sort-by=.status.containerStatuses[0].restartCount

sort via start time

$ kubectl -n <namespace> get po \
    --sort-by=.status.startTime

get the oldest pod

-1: means the last in the list

$ kubectl -n <namepsace> get pods \
    --sort-by=.metadata.creationTimestamp \
    -o jsonpath='{.items[-1:].metadata.name}'

sort via created time

$ kubectl -n <namespace> get pods \
    --sort-by=.metadata.creationTimestamp

run & create

pod

# create and login
$ kubectl run debug --image=busybox -it --rm
# create and sleep
$ kubectl run debug --image=busybox -- sleep infinity
pod/debug created
# created with specific nodeSelector
$ kubectl run debug \
              --image=busybox \
              --overrides='{"spec": { "nodeSelector": {"kubernetes.io/hostname": "k8s-node-01"} }}'

$ kubectl get pod
NAME    READY   STATUS    RESTARTS   AGE
debug   1/1     Running   0          6s

# delete
$ kubectl delete pod/debug
pod "debug" deleted

# attach
$ kubectl attach <pod-name> -c <container-name> -it
# i.e.:
$ kubectl attach debug -c debug -it

deploy

# format
$ kubectl create deployment <name> --image=<image:tag> [--replicas=n]
# i.e.:
$ kubectl create deployment nginx --image=nginx --replicas=2
deployment.apps/nginx created

# optional
$ kubectl scale deployment nginx --replicas=3

$ kubectl get pod
NAME                     READY   STATUS    RESTARTS   AGE
nginx-6799fc88d8-6clhp   1/1     Running   0          9s
nginx-6799fc88d8-cjz56   1/1     Running   0          9s

# delete
$ kubectl delete deployment nginx
deployment.apps "nginx" deleted

svc

$ kubectl expose deployment <name> --port=80 --target-port=9376

list

watch pods with timestamp

[!NOTE|label:references:]

• Append timestamp to kubernetes --watch-only command

$ kubectl get pods --watch-only |
  while read line ; do echo -e "$(date +"%Y-%m-%d %H:%M:%S.%3N")\t pods\t $line" ; done

list pod status with timestamp

[!NOTE|label:references:]

• Can kubectl describe show timestamp of pod events?

• via evnets

  $ kubectl get events -o custom-columns=FirstSeen:.firstTimestamp,LastSeen:.lastTimestamp,Count:.count,From:.source.component,Type:.type,Reason:.reason,Message:.message \
            --field-selector involvedObject.kind=Pod,involvedObject.name=<pod-name>

• via pod json

  $ kubectl get po <pod-name> -o json | jq -r '.status.conditions'
  [
    {
      "lastProbeTime": null,
      "lastTransitionTime": "2023-09-28T08:15:33Z",
      "status": "True",
      "type": "Initialized"
    },
    {
      "lastProbeTime": null,
      "lastTransitionTime": "2023-11-23T02:33:09Z",
      "message": "containers with unready status: [config-reload]",
      "reason": "ContainersNotReady",
      "status": "False",
      "type": "Ready"
    },
    {
      "lastProbeTime": null,
      "lastTransitionTime": "2023-11-23T02:33:09Z",
      "message": "containers with unready status: [config-reload]",
      "reason": "ContainersNotReady",
      "status": "False",
      "type": "ContainersReady"
    },
    {
      "lastProbeTime": null,
      "lastTransitionTime": "2023-09-28T08:15:16Z",
      "status": "True",
      "type": "PodScheduled"
    }
  ]

list pod with nodename

• filter

  $ kubectl get po --all-namespaces -o wide --field-selector spec.nodeName=<nodeName>

• list

  $ kubectl get pods \
                --all-namespaces \
                --output 'jsonpath={range .items[*]}{.spec.nodeName}{"\t"}{.metadata.namespace}{"\t"}{.metadata.name}{"\n"}{end}

• or list with custom-columns

  $ kubectl get pod \
                --all-namespaces
                -o=custom-columns=NAME:.metadata.name,STATUS:.status.phase,NODE:.spec.nodeName \

• list nodeName with podIP

  $ kubectl get pod \
                --all-namespaces \
                -o json |
                jq '.items[] | .spec.nodeName + " " + .status.podIP'

list all ready pods

[!NOTE|label:references]

• * imarslo : list all ready nodes

$ kubectl get pods --all-namespaces -o json |
          jq -r '.items[] | select(.status.phase = "Ready" or ([ .status.conditions[] | select(.type == "Ready") ] | length ) == 1 ) | .metadata.namespace + "\t" + .metadata.name'

• list all ImagePullBackOff pods

  [!NOTE|label:references]

  • How can I view pods with kubectl and filter based on having a status of ImagePullBackOff?

  $ kubectl get pod --all-namespaces \
                    -o=json |
                    jq '.items[]|select(any( .status.containerStatuses[]; .state.waiting.reason=="ImagePullBackOff"))|.metadata.name'
  
  # or
  $ kubectl get pod --all-namespaces \
                    -o jsonpath='{.items[?(@.status.containerStatuses[*].state.waiting.reason=="ImagePullBackOff")].metadata.name}'

list error status pods

reference:

• Viewing, finding resources

• kubectl get should have a way to filter for advanced pods status

$ kubectl -n <namespace> get po \
          --field-selector status.phase=Failed

list and delete all error status pods

$ for i in $(kubectl get po --no-headers --all-namespaces --field-selector status.phase=Failed -o=custom-columns=NAMESPACE:.metadata.namespace | sort -u); do
    kubectl -n $i delete po --field-selector status.phase=Failed --force --grace-period=0
  done

• or

  $ kubectl -n <namespace> delete po \
            --field-selector status.phase=Failed

• or

  $ kubectl -n <namespace> get po \
            --field-selector=status.phase!=Running

• or

  $ kubectl --all-namespaces get po \
            --field-selector=status.phase!=Running,status.phase!=Succeeded

• or

  $ kubectl get po --all-namespaces -o json  \
          | jq -r '.items[] \
          | select(.status.phase != "Running" \
                   or ([ .status.conditions[] | select(.type == "Ready" and .status == "False") ] | length ) == 1 \
                  ) \
          | .metadata.namespace + "/" + .metadata.name'

list all pods statuses only

$ kubectl -n <namespace> get po \
          -o=jsonpath='{.items[*].status.phase}'
Running Running Running Running Running Running Running Running Running

list running images

$ kubectl4 -n <namespace> get po -o jsonpath="{..image}" |
     tr -s '[[:space:]]' '\n' |
     sort |
     uniq -c
      2 gcr.io/kubernetes-helm/tiller:v2.14.3
      6 k8s.gcr.io/coredns:1.2.2
      6 k8s.gcr.io/etcd:3.2.24
      6 k8s.gcr.io/kube-apiserver:v1.12.3
      6 k8s.gcr.io/kube-controller-manager:v1.12.3
     30 k8s.gcr.io/kube-proxy:v1.12.3
      6 k8s.gcr.io/kube-scheduler:v1.12.3
      4 k8s.gcr.io/metrics-server-amd64:v0.3.6
     30 k8s.gcr.io/node-problem-detector:v0.8.1
      2 kubernetesui/dashboard:v2.0.0-beta1
      4 kubernetesui/metrics-scraper:v1.0.1
     60 quay.io/coreos/flannel:v0.10.0-amd64

list running pods

$ kubectl -n <namespace> get po \
          -o=custom-columns=NAME:.metadata.name,STATUS:.status.phase,NODE:.spec.nodeName
NAME                                        STATUS    NODE
coredns-59dd98b545-7t25l                    Running   k8s-node01
coredns-59dd98b545-lnklx                    Running   k8s-node02
coredns-59dd98b545-ltj5p                    Running   k8s-node03
...

list pods on nodes

• specific nodes

  $ kubectl get pods --all-namespaces \
                     -o wide \
                     --field-selector spec.nodeName=<node>

• all nodes

  $ kubectl get pods -o wide \
                     --sort-by="{.spec.nodeName}"

  • via label filter

    $ for n in $(kubectl get nodes -l your_label_key=your_label_value --no-headers | cut -d " " -f1); do
        kubectl get pods --all-namespaces  --no-headers --field-selector spec.nodeName=${n}
      done

  • via API

    $ curl --cacert ca.crt \
           --cert apiserver.crt \
           --key apiserver.key \
           https://<server>:<port>/api/v1/namespaces/<namespace>/pods?fieldSelector=spec.nodeName%3Dsomenodename

list all containers

[!NOTE|label:references:]

• List All Container Images Running in a Cluster

• list container images

  $ kubectl get po -o jsonpath="{.items[*].spec['initContainers', 'containers'][*].image}" |
            tr -s '[[:space:]]' '\n' |
            sort |
            uniq -c
        2 jenkins:2.452.2-lts-jdk17
        2 docker.io/kiwigrid/k8s-sidecar:1.27.4
  
  # or
  $ kubectl get pods -o go-template --template="{{range .items}}{{range .spec.containers}}{{.image}} {{end}}{{end}}"
  jenkins:2.452.2-lts-jdk17 docker.io/kiwigrid/k8s-sidecar:1.27.4

  • for all namespaces

    • list all container images in all namespaces

    $ kubectl get pods \
                  --all-namespaces \
                  -o jsonpath="{.items[*].spec.containers[*].image}" |
                  tr -s '[[:space:]]' '\n' |
                  sort |
                  uniq -c
    # or
    $ kubectl get pods \
                  --all-namespaces \
                  -o jsonpath="{.items[*].spec.containers[*].image}"

list container images by pod

$ kubectl get pods \
              --all-namespaces \
              -o=jsonpath='{range .items[*]}{"\n"}{.metadata.name}{":\t"}{range .spec.containers[*]}{.image}{", "}{end}{end}' |
              sort

• list container names

  $ kubectl get po -o jsonpath="{.items[*].spec['initContainers', 'containers'][*].name}" |
          tr -s '[[:space:]]' '\n' |
          sort |
          uniq -c
        1 config-reload
        1 config-reload-init
        1 init
        1 jenkins

• list container image by pod

  $ kubectl get po -o jsonpath='{range .items[*]}{"\n"}{.metadata.name}{":\t"}{range .spec.containers[*]}{.image}{", "}{end}{end}' | sort
  
  staging-jenkins-0:        jenkins:2.452.2-lts-jdk17, docker.io/kiwigrid/k8s-sidecar:1.27.4,

get port enabled in pod

$ kubectl get po jenkins-0 -o jsonpath='{.spec.containers[*].ports[*]}'
{"containerPort":8080,"name":"http","protocol":"TCP"} {"containerPort":50000,"name":"agent-listener","protocol":"TCP"} {"containerPort":50017,"name":"sshd-listener","protocol":"TCP"}

# or
$ kubectl get po jenkins-0 -o jsonpath="{range .spec.containers[*].ports[*]}{@.*}{'\n'}{end}" | column -t
http            8080   TCP
agent-listener  50000  TCP
sshd-listener   50017  TCP

get podIP

$ kubectl get po <pod-name> -o go-template='{{range .items}}{{.status.podIP}}{{"\n"}}{{end}}'
10.244.140.106

get the first deploy name in namespace

$ kubectl -n <namespace> get deploy -o=jsonpath={.items[0].metadata.name}

get all deploy names

$ kubectl -n <namespace> get deploy -o=jsonpath='{.items[*].metadata.name}'

item.metadata.name

• list via jsonpath={.items..metadata.name}

  $ kubectl -n kube-system get po --output=jsonpath={.items..metadata.name}
  coredns-c7ddbcccb-5cj5z coredns-c7ddbcccb-lxsw6 coredns-c7ddbcccb-prjfk ...

  • or

    $ kubectl -n kube-system get po -o jsonpath="{range .items[*]}{@.metadata.name}{'\n'}{end}" |
              head -10
    coredns-c7ddbcccb-5cj5z
    coredns-c7ddbcccb-lxsw6
    coredns-c7ddbcccb-prjfk
    etcd-node03
    etcd-node04
    etcd-node01
    kube-apiserver-node03
    kube-apiserver-node04
    kube-apiserver-node01
    kube-controller-manager-node03

output

references:

• Inspired from here

• Kubectl - Introduce "custom-columns" variant to add additional columns to output

-o name

$ kubectl -n kube-system get pods -o name | head
pod/coredns-c7ddbcccb-5cj5z
pod/coredns-c7ddbcccb-lxsw6
pod/coredns-c7ddbcccb-prjfk
pod/etcd-node03
pod/etcd-node04
pod/etcd-node01
pod/kube-apiserver-node03
pod/kube-apiserver-node04
pod/kube-apiserver-node01
pod/kube-controller-manager-node03

--template

$ kubectl -n kube-system get pods \
          -o go-template \
          --template '{{range .items}}{{.metadata.name}}{{"\n"}}{{end}}' |
          head
coredns-c7ddbcccb-5cj5z
coredns-c7ddbcccb-lxsw6
coredns-c7ddbcccb-prjfk
etcd-node03
etcd-node04
etcd-node01
kube-apiserver-node03
kube-apiserver-node04
kube-apiserver-node01
kube-controller-manager-node03

• or

  $ kubectl -n kube-system get pods \
            --template '{{range .items}}{{.metadata.name}}{{"\n"}}{{end}}' |
            head
  coredns-c7ddbcccb-5cj5z
  coredns-c7ddbcccb-lxsw6
  coredns-c7ddbcccb-prjfk
  etcd-node03
  etcd-node04
  etcd-node01
  kube-apiserver-node03
  kube-apiserver-node04
  kube-apiserver-node01
  kube-controller-manager-node03

custom-columns

• Name:.metadata.name

  $ kubectl get po --all-namespaces \
                   -o=custom-columns=NAMESPACE:.metadata.namespace

• NODE:.spec.nodeName

• IPS:status.podIPs

• PHASE:.status.phase

• RESTARTS:RESTART:.status.containerStatuses[0].restartCount

• IMAGE:.spec.containers[0].image

• CREATED:.metadata.creationTimestamp

• LABELS:.metadata.labels

• QOS-CLASS:.status.qosClass

list all images running in particular namespace

$ kubectl -n <namespace> get po \
          --output=custom-columns="NAME:.metadata.name,IMAGE:.spec.containers[*].image"

• list all images exclude 'k8s.gcr.io/coredns:1.6.2'

  $ kubectl --all-namespaces get pods \
            -o=custom-columns='DATA:spec.containers[?(@.image!="k8s.gcr.io/coredns:1.6.2")].image'

list via -o custom-columns=":metadata.name"

$ kubectl -n kube-system get pods -o custom-columns=":metadata.name" | head
coredns-c7ddbcccb-5cj5z
coredns-c7ddbcccb-lxsw6
coredns-c7ddbcccb-prjfk
etcd-node03
etcd-node04
etcd-node01
kube-apiserver-node03
kube-apiserver-node04
kube-apiserver-node01

QOS

$ kubectl -n kube-system get po \
          -o custom-columns=NAME:.metadata.name,NAMESPACE:.metadata.namespace,QOS-CLASS:.status.qosClass
NAME                                        NAMESPACE     QOS-CLASS
coredns-59dd98b545-7t25l                    kube-system   Burstable
coredns-59dd98b545-lnklx                    kube-system   Burstable
coredns-59dd98b545-ltj5p                    kube-system   Burstable
etcd-k8s-node01                             kube-system   BestEffort
etcd-k8s-node02                             kube-system   BestEffort
etcd-k8s-node03                             kube-system   BestEffort
kube-apiserver-k8s-node01                   kube-system   Burstable
kube-apiserver-k8s-node02                   kube-system   Burstable
kube-apiserver-k8s-node03                   kube-system   Burstable
kube-controller-manager-k8s-node01          kube-system   Burstable
kube-controller-manager-k8s-node02          kube-system   Burstable
kube-controller-manager-k8s-node03          kube-system   Burstable
kube-flannel-ds-amd64-627bn                 kube-system   Guaranteed
kube-flannel-ds-amd64-7hdqd                 kube-system   Guaranteed
kube-flannel-ds-amd64-b4th7                 kube-system   Guaranteed
...

management

execute in pod

$ kubectl -n devops exec -it devops-jenkins-659f4c6d44-d2w76 -- /bin/bash
jenkins@devops-jenkins-659f4c6d44-d2w76:/$ echo $HOME
/var/jenkins_home
jenkins@devops-jenkins-659f4c6d44-d2w76:/$ hostname
devops-jenkins-659f4c6d44-d2w76

restart po

reference:

• Restarting Kubernetes Pods

• How to Restarting Kubernetes Pods

• How to gracefully remove a node from Kubernetes? for kubernetes version 1.15+

• kubectl -n <namespace> rollout restart deployment <name>

$ kubectl -n <namespace> get po <po-name> -o yaml | kubectl replace --force -f -

• result

  $ kubectl -n <namespace> get po -w
  NAME                   READY    STATUS    RESTARTS   AGE
  mypo-659f4c6d44-72hb5   1/1     Running   0          47h
  mypo-659f4c6d44-72hb5   1/1     Terminating   0          47h
  mypo-659f4c6d44-d2w76   0/1     Pending       0          0s
  mypo-659f4c6d44-d2w76   0/1     Pending       0          0s
  mypo-659f4c6d44-d2w76   0/1     ContainerCreating   0          0s
  mypo-659f4c6d44-d2w76   1/1     Running             0          2s
  mypo-659f4c6d44-72hb5   0/1     Terminating         0          47h
  mypo-659f4c6d44-72hb5   0/1     Terminating         0          47h
  mypo-659f4c6d44-72hb5   0/1     Terminating         0          47h
  mypo-659f4c6d44-72hb5   0/1     Pending             0          0s
  mypo-659f4c6d44-72hb5   0/1     Terminating         0          0s
  mypo-659f4c6d44-72hb5   0/1     Terminating         0          0s
  mypo-659f4c6d44-72hb5   0/1     Terminating         0          0s
  mypo-659f4c6d44-72hb5   0/1     Terminating         0          1s
  mypo-659f4c6d44-72hb5   0/1     Terminating         0          1s

  • or

    $ kubectl -n <namespace> scale deployment <name> --replicas=0

resource managemenet

resource management for pods and containers

assign cpu resources to containers and pods

managing kubernetes resource limits

troubleshooting

[!NOTE|label:references:]

• How To Troubleshoot Kubernetes Pods: Beginners Guide

• simple pods

  # run-nginx.yml
  
  apiVersion: extensions/v1beta1
  kind: Deploy
  metadata:
    name: my-nginx
  spec:
    replicas: 2
    template:
      metadata:
        labels:
          run: my-ngxin
      spec:
        containers:
        - name: my-nginx
          image: nginx:1.10.1
          ports:
          - containerPort: 80

• kubectl run

  $ kubectl run ubuntu-marslo \
                --image=ubuntu:18.04 \
                --overrides='{"spec": { "nodeSelector": {"kubernetes.io/hostname": "k8s-node-01"}}}' \
                -- sleep infinity
  
  # or
  $ kubectl run ubuntu-marslo \
                --image=ubuntu:18.04 \
                --overrides='{"spec": { "nodeSelector": {"kubernetes.io/hostname": "k8s-node-01"}}}' \
                -it \
                --rm

debug svc

[!NOTE|labels:referencds:]

• DNS for Services and Pods

• svc in cluster can be visit via

  • CLUSTER-IP

  • <svc-name>.<namespace>.svc.cluster.local

# current svc
$ kubectl get svc
NAME      TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)              AGE
jenkins   ClusterIP   10.111.230.13   <none>        8080/TCP,30338/TCP   18h

# create new pod
$ kubectl run ubuntu-marslo \
              --image=ubuntu:18.04 \
              --overrides='{"spec": { "nodeSelector": {"kubernetes.io/hostname": "k8s-node-01"}}}' \
              -it \
              --rm

# check DNS
<ubuntu-marslo> $ cat /etc/resolv.conf
nameserver 10.96.0.10
search devops.svc.cluster.local svc.cluster.local cluster.local company.com
options ndots:5

# debug
$ nc -zv jenkins.devops.svc.cluster.local 30338
$ nc -zv 10.111.230.13                    30338
$ ssh -l marslo -p 30338 -i ~/.ssh/id_rsa jenkins.devops.svc.cluster.local list-plugins
$ ssh -l marslo -p 30338 -i ~/.ssh/id_rsa 10.111.230.13                    list-plugins