Kubectl¶

Kubectl is a command line tool for communicating with a Kubernetes Cluster's control pane, using the Kubernetes API.

Installation¶

On Windows (PowerShell)¶

Install Kubectl with chocolatey:

1	`choco install kubernetes-cli`

On Linux¶

[!INFO] Installing on WSL2 On WSL2 it's recommended to install Docker Desktop [[docker-desktop]], which automatically comes with kubectl.

Download the latest release¶

curl -LO "https://dl.k8s.io/release/$(curl -L -s https://dl.k8s.io/release/stable.txt)/bin/linux/amd64/kubectl"

Install kubectl¶

sudo install -o root -g root -m 0755 kubectl /usr/local/bin/kubectl

Config Management¶

Multiple Config Files¶

On Windows (PowerShell)¶

$env:KUBECONFIG = "$HOME/.kube/prod-k8s-clcreative-kubeconfig.yaml;$HOME/.kube/infra-home-kube-prod-1.yml;$HOME/.kube/infra-home-kube-demo-1.yml;$HOME/.kube/infra-cloud-kube-prod-1.yml"

On Linux¶

export KUBECONFIG=~/.kube/kube-config-1.yml:~/.kube/kube-config-2.yml

Managing multiple config files manually can become extensive. Below you can find a handy script, which you can implement in your shell rc file (e.g. .bashrc or .zshrc). The script will automatically add all found kubeconfigs to the KUBECONFIG environment variable.

Script was copied from here

# If there's already a kubeconfig file in ~/.kube/config it will import that too and all the contexts
DEFAULT_KUBECONFIG_FILE="$HOME/.kube/config"
if test -f "${DEFAULT_KUBECONFIG_FILE}"
then
  export KUBECONFIG="$DEFAULT_KUBECONFIG_FILE"
fi# Your additional kubeconfig files should be inside ~/.kube/config-files
ADD_KUBECONFIG_FILES="$HOME/.kube/config-files"
mkdir -p "${ADD_KUBECONFIG_FILES}"OIFS="$IFS"
IFS=$'\n'
for kubeconfigFile in `find "${ADD_KUBECONFIG_FILES}" -type f -name "*.yml" -o -name "*.yaml"`
do
    export KUBECONFIG="$kubeconfigFile:$KUBECONFIG"
done
IFS="$OIFS"

Another helpful tool that makes you changing and selecting the cluster context easier is kubectx. You can download kubectx here.

The above script conflicts with kubectx, cause kubectx can only work with one kubeconfig file listed in the KUBECONFIG env var. If you want to use both, add the following lines to your rc file.

# now we merge all configs to one
kubectl config view --merge --flatten > $HOME/.kube/merged-config
export KUBECONFIG="$HOME/.kube/merged-config"

Commands¶

Networking¶

Connect containers using Kubernetes internal DNS system: <service-name>.<namespace>.svc.cluster.local

Troubleshoot Networking with a netshoot toolkit Container: kubectl run tmp-shell --rm -i --tty --image nicolaka/netshoot -- /bin/bash

Containers¶

Restart Deployments (Stops and Restarts all Pods): kubectl scale deploy <deployment> --replicas=0 kubectl scale deploy <deployment> --replicas=1

Executing Commands on Pods: kubectl exec -it <PODNAME> -- <COMMAND> kubectl exec -it generic-pod -- /bin/bash

Config and Cluster Management¶

COMMAND	DESCRIPTION
`kubectl cluster-info`	Display endpoint information about the master and services in the cluster
`kubectl config view`	Get the configuration of the cluster
### Resource Management
COMMAND	DESCRIPTION
---	---
`kubectl get all --all-namespaces`	List all resources in the entire Cluster
`kubectl delete <RESOURCE> <RESOURCENAME> --grace-period=0 --force`	Try to force the deletion of the resource

List of Kubernetes Resources "Short Names"¶

Short Name	Long Name
`csr`	`certificatesigningrequests`
`cs`	`componentstatuses`
`cm`	`configmaps`
`ds`	`daemonsets`
`deploy`	`deployments`
`ep`	`endpoints`
`ev`	`events`
`hpa`	`horizontalpodautoscalers`
`ing`	`ingresses`
`limits`	`limitranges`
`ns`	`namespaces`
`no`	`nodes`
`pvc`	`persistentvolumeclaims`
`pv`	`persistentvolumes`
`po`	`pods`
`pdb`	`poddisruptionbudgets`
`psp`	`podsecuritypolicies`
`rs`	`replicasets`
`rc`	`replicationcontrollers`
`quota`	`resourcequotas`
`sa`	`serviceaccounts`
`svc`	`services`

陼 Logs and Troubleshooting¶

...

Logs¶

...

MySQL¶

kubectl run -it --rm --image=mysql:5.7 --restart=Never mysql-client -- mysql -u USERNAME -h HOSTNAME -p

Networking¶

kubectl run -it --rm --image=nicolaka/netshoot netshoot -- /bin/bash

Resources stuck in Terminating state¶

...

(
NAMESPACE=longhorn-demo-1
kubectl proxy &
kubectl get namespace $NAMESPACE -o json |jq '.spec = {"finalizers":[]}' >temp.json
curl -k -H "Content-Type: application/json" -X PUT --data-binary @temp.json 127.0.0.1:8001/api/v1/namespaces/$NAMESPACE/finalize
)