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Installation Using Kubeadm for a Single-Node Kubernetes Cluster

Kubeadm is a tool provided by Kubernetes to create and manage clusters. You can use Kubeadm to set up a single-node Kubernetes cluster on a single server (master node) and run your workloads there.

Step 1: Install Kubernetes Components You will need to install kubeadm, kubelet, and kubectl on your server.

For Ubuntu/Debian-based systems:

# Update the system
sudo apt update && sudo apt upgrade -y

# Install required packages
sudo apt install -y apt-transport-https ca-certificates curl

# Add Kubernetes APT repository
curl -s https://packages.cloud.google.com/apt/doc/apt-key.gpg | sudo apt-key add -
sudo apt update

# Install Kubernetes components
sudo apt install -y kubelet kubeadm kubectl

Error Debugging

I got this error when I executed the last command.

No apt package "kubeadm", but there is a snap with that name.
Try "snap install kubeadm"

No apt package "kubectl", but there is a snap with that name.
Try "snap install kubectl"

No apt package "kubelet", but there is a snap with that name.
Try "snap install kubelet"

So, I do this recommend.

1. Install Snap (if not already installed)

If snap is not installed on your system, you can install it with the following commands:

sudo apt update
sudo apt install snapd

2. Install kubeadm, kubectl, and kubelet using Snap

Once snapd is installed, you can use it to install the Kubernetes tools. Use the following commands:

sudo snap install kubeadm --classic
sudo snap install kubectl --classic
sudo snap install kubelet --classic

The --classic flag ensures that the snaps are installed in classic mode, which allows them to have access to system resources outside of the snap sandbox.

3. Verify the Installation

After installation, you can check if the tools are properly installed by running:

kubeadm version
kubectl version --client
kubelet --version

Step 2: Disable Swap Memory (Required for Kubernetes)

Kubernetes requires that swap memory is disabled. To disable swap:

sudo swapoff -a

To permanently disable swap, comment out the swap entry in /etc/fstab.

Step 3: Install containerd

sudo apt-get install -y containerd
sudo systemctl start containerd
sudo systemctl enable containerd
sudo systemctl status containerd

Step 4: Initialize the Kubernetes Cluster

Run the following command to initialize the Kubernetes cluster:

sudo kubeadm init --pod-network-cidr=10.244.0.0/16

The --pod-network-cidr is the CIDR block for your pods and is required for setting up the network plugin (Flannel, in this case).

Once this command completes successfully, you'll see output that provides a kubeadm join command for adding worker nodes (though in this case, we are using a single node, so you won’t need to add more nodes).

Error Debugging

I found this following error when I executed the command:

W1201 05:51:43.292057   13491 checks.go:1080] [preflight] WARNING: Couldn't create the interface used for talking to the container runtime: failed to create new CRI runtime service: validate service connection: validate CRI v1 runtime API for endpoint "unix:///var/run/containerd/containerd.sock": rpc error: code = Unavailable desc = connection error: desc = "transport: Error while dialing: dial unix /var/run/containerd/containerd.sock: connect: no such file or directory"
        [WARNING FileExisting-crictl]: crictl not found in system path
        [WARNING Service-Kubelet]: kubelet service is not enabled, please run 'systemctl enable kubelet.service'
error execution phase preflight: [preflight] Some fatal errors occurred:
        [ERROR NumCPU]: the number of available CPUs 1 is less than the required 2
        [ERROR FileExisting-conntrack]: conntrack not found in system path
        [ERROR FileContent--proc-sys-net-ipv4-ip_forward]: /proc/sys/net/ipv4/ip_forward contents are not set to 1
[preflight] If you know what you are doing, you can make a check non-fatal with `--ignore-preflight-errors=...`
To see the stack trace of this error execute with --v=5 or higher

The problem was my node didn't pass the requirement. The requirement for a node is 2 CPUs. So, I upgraded my node to become 2 CPUs.

Step 4: Ensure that the kubelet is Enabled and Running

sudo snap start kubelet
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