Setting up the Kubernetes Command-Line Interface (kubectl)

3 Setting up the Kubernetes Command-Line Interface (kubectl)

This chapter describes how to set up the Kubernetes CLI (kubectl). The kubectl command is part of Kubernetes and is used to create and manage the containerized applications you deploy on the Kubernetes cluster.

The kubectl utility is a command line tool that interfaces with the Kubernetes API server to run commands against the Kubernetes cluster. The kubectl command is typically run on a control plane node of the cluster (the recommended option), although you can set up kubectl access on an external node that's not in the cluster, if required. The kubectl utility effectively grants full administrative rights to the cluster and all nodes in the cluster.

This chapter discusses setting up the kubectl command to access a Kubernetes cluster from either a control plane node or an external node (not part of the Kubernetes cluster).

Setting up kubectl on a Control Plane Node

To set up the kubectl command on a control plane node, copy, and paste these commands to a terminal in the home directory on a control plane node:

mkdir -p $HOME/.kube
sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
sudo chown $(id -u):$(id -g) $HOME/.kube/config
export KUBECONFIG=$HOME/.kube/config
echo 'export KUBECONFIG=$HOME/.kube/config' >> $HOME/.bashrc

Verify that you can use the kubectl command using any kubectl command such as:

kubectl get pods --all-namespaces

The output looks similar to:

NAMESPACE              NAME                          READY   STATUS    RESTARTS   AGE
externalip-validat...  externalip-validation-...     1/1     Running   0          1h
kube-system            coredns-...                   1/1     Running   0          1h
kube-system            coredns-...                   1/1     Running   0          1h
kube-system            etcd-...                      1/1     Running   2          1h
kube-system            etcd-...                      1/1     Running   2          1h
kube-system            kube-apiserver-...            1/1     Running   2          1h
kube-system            kube-apiserver-...            1/1     Running   2          1h
kube-system            kube-controller-manager-...   1/1     Running   5 (1h ago) 1h
kube-system            kube-controller-manager-...   1/1     Running   2          1h
kube-system            kube-flannel-...              1/1     Running   0          1h
kube-system            kube-flannel-...              1/1     Running   0          1h
kube-system            kube-flannel-...              1/1     Running   0          1h
kube-system            kube-proxy-...                1/1     Running   0          1h
kube-system            kube-proxy-...                1/1     Running   0          1h
kube-system            kube-proxy-...                1/1     Running   0          1h
kube-system            kube-scheduler-...            1/1     Running   5 (1h ago) 1h
kube-system            kube-scheduler-...            1/1     Running   2          1h
kubernetes-dashboard   kubernetes-dashboard-...      1/1     Running   0          1h

Setting up kubectl on a Non-Cluster Node

Oracle Cloud Native Environment lets you create many environments from the operator node. With this in mind, we recommend that you use kubectl on a control plane node in the Kubernetes cluster. If you use kubectl from outside the cluster, and you have many environments deployed, you might inadvertently manage an unexpected Kubernetes cluster. However, if you need to set up kubectl to run from outside the cluster, you need to configure it.

The following example shows you how to set up a host that's not in the cluster with kubectl to access to a Kubernetes cluster.

Note:

The following example assumes the OS of the node is Oracle Linux. However, you can also set up kubectl on macOS and Microsoft Windows hosts by leveraging the Kubernetes community package. For Microsoft Windows hosts you also need to install Windows Subsystem for Linux 2 (WLS 2).

To set up kubectl on a host that's not in the cluster:

On the operator node, use the olcnectl module property get command to get the Kubernetes configuration file for the cluster:
```
olcnectl module property get \
--environment-name myenvironment \
--name mycluster \
--property kubecfg | base64 -d > kubeconfig.yaml
```
A file named kubeconfig.yaml is created that contains the Kubernetes configuration information required to access the cluster.
Set up the Kubernetes file on the host. Log in to the host and copy the kubeconfig.yaml from the operator node to a local directory on the host.

Caution:

Follow security best practices when copying a configuration file with sensitive information between hosts.
1. Create a subdirectory named .kube in the home directory:
```
mkdir -p $HOME/.kube
```
2. Copy the kubeconfig.yaml file to the .kube directory:
```
cp /path_to_file/kubeconfig.yaml $HOME/.kube/config
```
3. Export the path to the file for the KUBECONFIG environment variable:
```
export KUBECONFIG=$HOME/.kube/config
```
4. To permanently set this environment variable, add it to the .bashrc file:
```
echo 'export KUBECONFIG=$HOME/.kube/config' >> $HOME/.bashrc
```
Install kubectl on the host.

Set up the node with the required access to Oracle Cloud Native Environment packages by enabling repositories or channels as required. See Getting Started for more information.
Install kubectl:
```
sudo dnf install kubectl
```

Verify you can use the kubectl command:

kubectl get pods -n kube-system

The output looks similar to:

NAME                                    READY   STATUS    RESTARTS   AGE
coredns-5bc65d7f4b-qzfcc                1/1     Running   0          23h
coredns-5bc65d7f4b-z64f2                1/1     Running   0          23h
etcd-control1.example.com               1/1     Running   0          23h
kube-apiserver-control1.example.com     1/1     Running   0          23h
kube-controller-control1.example.com    1/1     Running   0          23h
...