# Kubectl

Kubectl is a command line tool for communicating with a [Kubernetes Cluster](kubernetes/kubernetes.md)'s control pane, using the Kubernetes API.

Documentation: [Kubectl Reference](https://kubernetes.io/docs/reference/kubectl/)

---
## Installation

### On Windows (PowerShell)

Install Kubectl with [chocolatey](tools/chocolatey.md):

```
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

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

#### Install kubectl

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

### On mac OS

Install Kubectl with [homebrew](tools/homebrew.md):

```zsh
brew install kubernetes-cli
```

---
## Config Management

### Multiple Config Files

### On Windows (PowerShell)

```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

```bash
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](https://medium.com/@alexgued3s/multiple-kubeconfigs-no-problem-f6be646fc07d)

```bash
# 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](https://github.com/ahmetb/kubectx).

:warning: 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.

```bash
# 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
...

```sh
(
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
)
```