CSLAB Kubernetes Access Guide and Usage Examples

1. Introduction

This guide explains how to connect to the CSLAB infrastructure through VPN, install the required tools, set up your local working environment, and run Kubernetes (k8s) tasks.

Kubernetes (K8s) is an open-source platform for managing containerized applications at scale. It helps automate deployment, management, and scaling of applications.

You will also receive an email containing two configuration files and a username for accessing the infrastructure. In the instructions below, whenever you see <username>, replace it with the username you received by email.

The material is available in the following repository:

https://github.com/cslab-ntua/cslab-k8s-access

You can clone it locally with:

cd ~
git clone https://github.com/cslab-ntua/cslab-k8s-access

This command copies the entire repository to your local machine. Since the repository may be updated regularly, make sure you keep it up to date by running:

cd cslab-k8s-access
git pull

2. Installing OpenVPN Client, kubectl, and k9s

To connect to the infrastructure, first install the OpenVPN client.

After installing it, import the .ovpn file you received by email and connect to the VPN.

Installing kubectl

kubectl is the command-line tool for managing Kubernetes clusters. Install it on a Linux machine or WSL using the commands below:

# Install the basic packages required for HTTPS repositories
sudo apt-get install -y apt-transport-https ca-certificates curl gnupg

# Download and store the public key for the Kubernetes repository
curl -fsSL https://pkgs.k8s.io/core:/stable:/v1.32/deb/Release.key | sudo gpg --dearmor -o /etc/apt/keyrings/kubernetes-apt-keyring.gpg

# Set the correct permissions on the key file
sudo chmod 644 /etc/apt/keyrings/kubernetes-apt-keyring.gpg

# Add the Kubernetes repository to the apt sources list
echo 'deb [signed-by=/etc/apt/keyrings/kubernetes-apt-keyring.gpg] https://pkgs.k8s.io/core:/stable:/v1.32/deb/ /' | sudo tee /etc/apt/sources.list.d/kubernetes.list

# Set the correct permissions on the repository file
sudo chmod 644 /etc/apt/sources.list.d/kubernetes.list

# Update the apt package index
sudo apt-get update

# Install kubectl
sudo apt-get install -y kubectl

# Create the ~/.kube directory where the config file will be stored
mkdir ~/.kube

Next, place the config file you received by email in ~/.kube/config so that kubectl can connect to the Kubernetes infrastructure.

To do this, copy the config file from the location where you originally downloaded it on your host machine (for example, Windows) into the ~/.kube directory inside Linux/WSL.

Assume that you downloaded the config file into your Windows user's Downloads folder.

Run the following commands inside WSL Linux, replacing <username> with your Windows username. For example, in my case the path is /mnt/c/Users/ikons/Downloads/config.

# Go to your home directory
cd

# Create the .kube directory if it does not already exist
mkdir .kube

# Copy the config file from the Windows file system into WSL
cp /mnt/c/Users/<username>/Downloads/config ~/.kube/config

You can also do this through Windows Explorer by browsing to the Linux folder.

Installing k9s

k9s is a terminal-based tool for monitoring and managing Kubernetes clusters. Install it with:

wget https://github.com/derailed/k9s/releases/download/v0.40.10/k9s_linux_amd64.deb
sudo dpkg -i k9s_linux_amd64.deb
echo "export KUBE_EDITOR=nano" >> ~/.bashrc

k9s uses the same configuration file: ~/.kube/config.

Monitoring Workloads with k9s

To monitor the workload you just submitted, run:

k9s

Useful k9s Commands

Show pods:

:pods

View the logs of a pod:

l

Inspect the status/details of a pod:

d

3. Writing a Manifest and Running It with kubectl

A manifest is a YAML file that describes Kubernetes resources. You can create and apply these files using kubectl apply.

Go to the repository directory:

cd ~/cslab-k8s-access

The example Pod manifest is available at manifest/nginx-pod.yaml.

Example Pod Manifest (manifest/nginx-pod.yaml)

apiVersion: v1
kind: Pod
metadata:
  name: nginx
spec:
  containers:
    - name: nginx
      image: nginx:latest
      ports:
        - containerPort: 80

To create the Pod shown above:

kubectl apply -f manifest/nginx-pod.yaml

To verify that the Pod was created successfully:

kubectl get pod nginx -o wide

You should see output similar to this:

NAME    READY   STATUS    RESTARTS   AGE     IP               NODE              NOMINATED NODE   READINESS GATES
nginx   1/1     Running   0          7h34m   10.233.101.168   source-code-pc6   <none>           <none>

You can use the Pod IP address to open it in your browser and view the default nginx welcome page:

http://10.233.101.168

4. Cleanup

Once you have confirmed that the nginx Pod is running correctly and serving the default nginx page, you can remove it from the cluster with:

# Delete the Pod
kubectl delete -f manifest/nginx-pod.yaml