Used Kubernetes for the First Time

I’ve never used Kubernetes before, and for the first time, I’m using it. This is what I’ve learned so far.

For this, I did not use any cloud service. I had to create a local Kubernetes cluster and deploy an application using it.

This time, I had just set up a new system with Ubuntu, so this post contains the installation steps for Ubuntu instead of Fedora. Here are the steps:

setup

Update the repositories

sudo apt update

prerequisites

curl: need to download stuff over http.
ca-certificates: need updated ca-certificate details.
apt-transport-https: not sure why I had to install this one. ppas,
gnupg: as the installation requires you would need gnupg the details can be found here
Docker: you would need docker to run containers, although kubernetes can make use of podman and other tools as well, I just used docker, if it was fedora, I would have used podman as it comes pre installed with fedora.

sudo apt install apt-transport-https ca-certificates curl gnupg -y

to install docker

# Add Docker's official GPG key:
sudo install -m 0755 -d /etc/apt/keyrings
sudo curl -fsSL https://download.docker.com/linux/ubuntu/gpg -o /etc/apt/keyrings/docker.asc
sudo chmod a+r /etc/apt/keyrings/docker.asc

# Add the repository to Apt sources:
echo \
  "deb [arch=$(dpkg --print-architecture) signed-by=/etc/apt/keyrings/docker.asc] https://download.docker.com/linux/ubuntu \
  $(. /etc/os-release && echo "$VERSION_CODENAME") stable" | \
  sudo tee /etc/apt/sources.list.d/docker.list > /dev/null
sudo apt update

# Install docker-ce
sudo apt install docker-ce docker-ce-cli containerd.io \
     docker-buildx-plugin docker-compose-plugin -y

add Kubernetes ppas and install Kubernetes tools

echo "deb [signed-by=/etc/apt/keyrings/kubernetes-apt-keyring.gpg] https://pkgs.k8s.io/core:/stable:/v1.30/deb/ /" | sudo tee /etc/apt/sources.list.d/kubernetes.list
curl -fsSL https://pkgs.k8s.io/core:/stable:/v1.30/deb/Release.key | sudo gpg --dearmor -o /etc/apt/keyrings/kubernetes-apt-keyring.gpg
sudo apt update
sudo apt install -y kubelet kubectl

install kind, since it is a local Kubernetes cluster, I went ahead with kind instead of minikube
- kind is not packaged for debian, you need to install it using go install so need to install go first.
- Once go is installed, kind can be installed with
```
go install sigs.k8s.io/kind@v0.23.0
```

At this point I had following tools installed

kubelet
kubectl
kind

I also like bash completions, so I added the alias and completions for kubectl in the bashrc.

echo 'alias k=kubectl' >>~/.bashrc
echo 'complete -F __start_kubectl k' >>~/.bashrc

At this point the installation is complete, now I had to create a cluster and deploy an application.

First thing was to create/initialize a master node for kuberenets.

girish in ~ as 👩‍💻 
🕙 02:23:52 ❯ kind create cluster
Creating cluster "kind" ...
 ✓ Ensuring node image (kindest/node:v1.30.0) 🖼
 ✓ Preparing nodes 📦  
 ✓ Writing configuration 📜
 ✓ Starting control-plane 🕹️
 ✓ Installing CNI 🔌
 ✓ Installing StorageClass 💾
Set kubectl context to "kind-kind"
You can now use your cluster with:

kubectl cluster-info --context kind-kind

Not sure what to do next? 😅  Check out https://kind.sigs.k8s.io/docs/user/quick-start/

girish in ~ as 👩‍💻  took 11s
🕙 02:24:09 ❯ kubectl cluster-info --context kind-kind
Kubernetes control plane is running at https://127.0.0.1:38079
CoreDNS is running at https://127.0.0.1:38079/api/v1/namespaces/kube-system/services/kube-dns:dns/proxy

To further debug and diagnose cluster problems, use 'kubectl cluster-info dump'.

Once this is done, I could query the nodes using

girish in ~ as 👩‍💻 
🕙 02:24:17 ❯ k get nodes
NAME                 STATUS   ROLES           AGE     VERSION
kind-control-plane   Ready    control-plane   4m44s   v1.30.0

Although at this point there are no pods running, I could check that using

girish in ~ as 👩‍💻 
🕙 02:28:50 ❯ k get pods
No resources found in default namespace.

At this point I decided to deploy local-paste which I still use.

girish in ~
🕙 01:39:23 ✖  k create deployment lp --image=girish946/local-paste
deployment.apps/lp created

girish in ~ as 👩‍💻 
🕙 01:40:22 ❯ k get pods
NAME                  READY   STATUS    RESTARTS   AGE
lp-6fb7957b86-pdq4h   1/1     Running   0          43s

In order to use the application, I had to expose the deployment as a service. to do that, I used the following command.

girish in ~
🕙 01:40:42 ❯ k expose deployment lp --port=8000 --type=NodePort
service/lp exposed

What this does is, it exposes the deployment lp on port 8000 and the type of service is NodePort. I could check the service using

girish in ~ as 👩‍💻 
🕙 02:33:16 ❯ k get svc
NAME         TYPE        CLUSTER-IP    EXTERNAL-IP   PORT(S)          AGE
kubernetes   ClusterIP   10.96.0.1     <none>        443/TCP          10m
lp           NodePort    10.96.9.107   <none>        8000:31788/TCP   79s

Now I could access the application using the IP of the master node and the port provided by the service.

To find out the IP of the master node, I could use

girish in ~ as 👩‍💻 
🕙 02:34:27 ❯ kubectl get nodes -o wide | awk -v OFS='\t\t' '{print $1, $6, $7}'
NAME  INTERNAL-IP  EXTERNAL-IP
kind-control-plane  172.18.0.2  <none>

From the two commands above, the Ip and the port for accessing local-paste was, 172.18.0.2 and 31788.

girish in ~ as 👩‍💻 
🕙 02:37:18 ✖  curl 172.18.0.2:31788/api/CreateDb
{"CreateDb": "Success"}

And now I could use use a browser to access the application.

kubernetes

To sum up, the Kubernetes terminology that I learnt was

cluster: a set of nodes that run containerized applications.
nodes: the machines that run the applications.
pods: the smallest unit of Kubernetes, it can contain one or more containers.

Also there are multiple tools to create and manage kube clusters, I used kind for this post, but there are others like minikube and kubeadm as well. I did try kubeadm but it was a bit more involved than kind.

Probably in the next post I’ll try to deploy a more complex application or try to deploy it on a cloud service.