t
Kubectl
- Generate a Pod (remove dry-run if you want to apply it)
$ kubectl run --generator=run-pod/v1 example --image=ubuntu --dry-run=client -o yaml --command=true sleep 10- Run a debug container in a pod
$ kubectl debug -it my-test-data-connector-747964d7c5-6nrck -n trendminer --image ubuntu- Query the api server from within a Pod
# Make sure the serviceaccount used by the Pod has permissions
curl https://kubernetes.default.svc/openapi/v2 --cacert /run/secrets/kubernetes.io/serviceaccount/ca.crt --header "Authorization: Bearer $(cat /run/secrets/kubernetes.io/serviceaccount/token)"- Use custom columns to get the name of the pods
$ kubectl get pods -l app=my-config-hub -o custom-columns=":metadata.name" --no-headers
my-config-hub-5b85796fb7-qprs2
* Spin up debug container
```sh
kubectl run -it --rm --image=ubuntu -- bash- See the
requests.limitenforced in the container
# If you specify a limit for your memory, you can see this being reflected via cgroups in the container.
# In this case the limit was set to '4861Mi' which correspondents with '5097127936' bytes
$ kubectl exec -n trendminer my-zeppelin-648745f8c-vft6s -ti /bin/sh
# cgroups v2
$ cat /sys/fs/cgroup/memory/memory.limit_in_bytes
5097127936- Port forward the ‘test’ deployment to port
8080of the node
kubectl port-forward deployment-test 8080Merge Multiple Kubeconfig Files
- Copy the target
kubeconfigfiles to your machine - Install the
konfigplugin for kubectl viakrew
$ kubectl krew install konfig- Import the target kubeconfig files
$ kubectl krew import --save /tmp/config1
$ kubectl krew import --save /tmp/config2- List the contexts
$ kubectl config get-contexts
CURRENT NAME CLUSTER AUTHINFO NAMESPACE
* cluster1 cluster1 clusterUser_rg-aks-internal_aks-internal
cluster2 cluster2 default
- Switch to a different context
$ kubectl config use-context cluster2
Switched to context "cluster2".$ kubectl config get-contexts
CURRENT NAME CLUSTER AUTHINFO NAMESPACE
cluster1 cluster1 clusterUser_rg-aks-internal_aks-internal
* cluster2 cluster2 default
Directly Query Kubelet Metrics
You can directly query the metrics of a kubelet using the following endpoints. This can come in handy if you for instance want to know the current imageFs used.
$ kubectl get --raw "/api/v1/nodes/my-test-turing31/proxy/stats/summary"
$ kubectl get --raw "/api/v1/nodes/my-test-turing31/proxy/metrics/resource"Use Custom Columns via Kubectl
$ kubectl get pods -A -o custom-columns=":metadata.name,:metadata.namespace,:spec.containers[0].image"
my-postgres-configuration-qgcgst-2j5xd trendminer docker.trendminer.net:5000/my-postgres-configuration:1.0.2203211626
my-assets-6fb5c89b88-8f9qm trendminer docker.trendminer.net:5000/my-assets:2.8.4
my-keycloak-674dd87744-4k5vg trendminer docker.trendminer.net:5000/my-keycloak:1.0.2203181320-3671586
my-compute-6d89c67689-2x6wj trendminer docker.trendminer.net:5000/my-compute:1.2.2203221403-426c403
ingress-nginx-controller-6965799df6-tfj7d ingress-nginx k8s.gcr.io/ingress-nginx/controller:v1.1.1
my-config-hub-7b89bb449b-88r69 trendminer docker.trendminer.net:5000/my-config-hub:1.0.2203211437-f9c6c68
my-hps-8655f6c9c4-p79w2 trendminer docker.trendminer.net:5000/my-hps:2.3.2203211840-10f1366
my-datasource-587974797c-vvt24 trendminer docker.trendminer.net:5000/my-datasource:1.0.2203231409-d1b1a9a
coredns-5789895cd-2cnmf kube-system rancher/mirrored-coredns-coredns:1.8.6Delete All Pods in Failed State
$ kubectl delete pods -A --field-selector status.phase=FailedDirectly Communicate with Kubernetes API via Curl
- You can directly send a request to the Kubernetes API server. You do however need to specify certificates.
client-admin.crt: this is the client certificate representing that you are doing this request as the ‘admin’ userclient-admin.key: this is the key matching the certificateca-cert.crt: the certificate authority used to sign all certificates in the cluster- All these certificates are generated by k3s automatically in
/mnt/data/kubernetes/k3s/server/tls/
$ curl -v --cert /tmp/client-admin.crt --key /tmp/client-admin.key --cacert /tmp/server-ca.crt https://10.92.94.77:6443/version
{
"major": "1",
"minor": "23",
"gitVersion": "v1.23.4+k3s1",
"gitCommit": "43b1cb48200d8f6af85c16ed944d68fcc96b6506",
"gitTreeState": "clean",
"buildDate": "2022-02-24T22:38:17Z",
"goVersion": "go1.17.5",
"compiler": "gc",
"platform": "linux/amd64"
}%Delete All Pods in All Namespaces
$ kubectl delete --all pods --all-namespaces
Generate YAML Manifests via CLI
You can generate any manifest file using the kubectl create --dry-run=client command. Use the -h argument if you are not sure what the options are.
$ kubectl create --dry-run=client role -o yaml x --verb=get,list,watch --resource=job
apiVersion: rbac.authorization.k8s.io/v1
kind: Role
metadata:
creationTimestamp: null
name: x
rules:
- apiGroups:
- batch
resources:
- jobs
verbs:
- get
- listQuickly search API
You can very easily and interactively search available fields in the API using kubectl explain and kubectl explore.
❯ kubectl explain deployment.spec.template
GROUP: apps
KIND: Deployment
VERSION: v1
FIELD: template <PodTemplateSpec>
DESCRIPTION:
Template describes the pods that will be created. The only allowed
template.spec.restartPolicy value is "Always".
PodTemplateSpec describes the data a pod should have when created from a
template
FIELDS:
metadata <ObjectMeta>
Standard object's metadata. More info:
https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#metadata
spec <PodSpec>
Specification of the desired behavior of the pod. More info:
https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#spec-and-statusThe explore plugin can be used to interactively search available fields. However this is a plugin that needs to be installed with krew.
❯ kubectl explore deployment.specK9s
Plugins
You can use plugins to add custom functionality. Copy your plugins to ~/.config/k9s/plugin.yml.
- Add debug containers via ‘shift-d’
plugins:
#--- Create debug container for selected pod in current namespace
# See https://kubernetes.io/docs/tasks/debug/debug-application/debug-running-pod/#ephemeral-container
debug:
shortCut: Shift-D
description: Add debug container
dangerous: true
scopes:
- containers
command: bash
background: false
confirm: true
args:
- -c
- 'kubectl debug -it --context $CONTEXT -n=$NAMESPACE $POD --target=$NAME --image=nicolaka/netshoot:v0.12 --share-processes -- bash'