Install and Setup Kubernetes Cluster on Ubuntu 24.04

This tutorial provides a step by step guide on how to install and setup Kubernetes Cluster on Ubuntu 24.04. Kubernetes, according to kubernetes.io, is an open-source production-grade container orchestration platform. It facilitates automated deployment, scaling and management of containerized applications.

Install and Setup Kubernetes Cluster on Ubuntu 24.04

Kubernetes Cluster Architecture

In this tutorial, we are going install and setup a four node (one control plane and three worker nodes) Kubernetes cluster.

A Kubernetes cluster is composed a Master node which hosts the control plane and a Worker node which hosts Pods.

Check our guide on a high-level overview of Kubernetes cluster to understand more on this.

Kubernetes Architecture: A High-level Overview of Kubernetes Cluster Components

Below are our node details.

Run System Update on Cluster Nodes

To begin with, update system package cache on all the nodes;

sudo apt update

Disable Swap on Cluster Nodes

Running Kubernetes requires that you disable swap.

Check if swap is enabled.

swapon --show

NAME      TYPE SIZE USED PRIO
/swap.img file   2G   0B   -2

If there is no output, then swap is not enabled. If it is enabled as shown in the output above, run the command below to disable it.

sudo swapoff -v /swap.img

Or simply

sudo swapoff -a

To permanently disable swap, comment out or remove the swap line on /etc/fstab file.

sudo sed -i '/swap/s/^/#/' /etc/fstab

or Simply remove it;

sed "-i.bak" '/swap/d' /etc/fstab

Enable Kernel IP forwarding on Cluster Nodes

In order to permit the communication between Pods across different networks, the system should able to route traffic between them. This can be achieved by enabling IP forwarding. Without IP forwarding, containers won’t be able to communicate with resources outside of their network namespace, which would limit their functionality and utility.

To enable IP forwarding, set the value of net.ipv4.ip_forward to 1.

echo "net.ipv4.ip_forward=1" | sudo tee -a  /etc/sysctl.conf

Apply the changes;

sudo sysctl -p

Load Some Required Kernel Modules on Cluster Nodes

overlay module provides support for the overlay filesystem. OverlayFS is type of union filesystem used by container runtimes to layer the container’s root filesystem over the host filesystem.

br_netfilter module provides support for packet filtering in Linux bridge networks based on various criteria, such as source and destination IP address, port numbers, and protocol type.

Check if these modules are enabled/loaded;

sudo lsmod | grep -E "overlay|br_netfilter"

br_netfilter           32768  0
bridge                307200  1 br_netfilter
overlay               151552  9

If not loaded, just load them as follows;

echo 'overlay
br_netfilter' | sudo tee /etc/modules-load.d/kubernetes.conf

sudo modprobe overlay

sudo modprobe br_netfilter

Similarly, enable Linux kernel’s bridge netfilter to pass bridge traffic to iptables for filtering. This means that the packets that are bridged between network interfaces can be filtered using iptables/ip6tables, just as if they were routed packets.

sudo tee -a /etc/sysctl.conf << 'EOL'
net.bridge.bridge-nf-call-iptables  = 1
net.bridge.bridge-nf-call-ip6tables = 1
EOL

Apply the changes;

sudo sysctl -p

Install Container Runtime on Ubuntu 24.04

Kubernetes uses container runtime to run containers in Pods. It supports multiple container runtimes including Docker Engine, containerd, CRI-O, Mirantis Container Runtime.

Install Containerd Runtime on all Cluster Nodes

In this demo, we will use containerd runtime. Therefore, on all nodes, master and workers, you need to install containerd runtime.

You can install containerd using official binaries or from the Docker Engine APT repos. We will use the later in this guide, thus;

sudo apt install apt-transport-https \
	ca-certificates curl \
	gnupg-agent \
	software-properties-common

curl -fsSL https://download.docker.com/linux/ubuntu/gpg | \
sudo gpg --dearmor -o /etc/apt/trusted.gpg.d/docker.gpg

echo "deb [arch=amd64] https://download.docker.com/linux/ubuntu $(lsb_release -sc) stable" | sudo tee /etc/apt/sources.list.d/docker-ce.list

sudo apt update

Install containerd;

sudo apt install -y containerd.io

The kubelet automatically detects the container runtime present on the node and uses it to run the containers.

Configure Cgroup Driver for ContainerD

Cgroup (control groups) is a Linux kernel feature that allows for the isolation, prioritization, and monitoring of system resources like CPU, memory, and disk I/O for a group of processes. Kubernetes (kubelet and container runtime such as containerd) uses cgroup drivers to interface with control groups in order to manage and set limit for the resources allocated to the containers.

Kubernetes support three types of Cgroup drivers;

• cgroupfs (control groups filesystem): This is the default cgroup driver used by Kubernetes kubelet to manage resources for containers.
• systemd: This is the default initialization system and service manager in some Linux systems. it offers functions such as starting of daemons, keeping track of processes using Linux cgroups etc.

For systems that use Systemd as their default Init system, it is recommended to use systemd cgroup driver for Kubernetes instead of cgroupfs.

The default configuration file for containerd is /etc/containerd/config.toml. When containerd is installed from Docker APT repos, this file is created with little configs. If installed from the official binaries, the containerd confguration file is not created.

Either way, update the containerd configuration file by executing the command below;

[ -d /etc/containerd ] || sudo mkdir /etc/containerd

containerd config default | sudo tee /etc/containerd/config.toml

Sample configuration.

disabled_plugins = []
imports = []
oom_score = 0
plugin_dir = ""
required_plugins = []
root = "/var/lib/containerd"
state = "/run/containerd"
temp = ""
version = 2

[cgroup]
  path = ""

[debug]
  address = ""
  format = ""
  gid = 0
  level = ""
  uid = 0

[grpc]
  address = "/run/containerd/containerd.sock"
  gid = 0
  max_recv_message_size = 16777216
  max_send_message_size = 16777216
  tcp_address = ""
  tcp_tls_ca = ""
  tcp_tls_cert = ""
  tcp_tls_key = ""
  uid = 0

[metrics]
  address = ""
  grpc_histogram = false

[plugins]

  [plugins."io.containerd.gc.v1.scheduler"]
    deletion_threshold = 0
    mutation_threshold = 100
    pause_threshold = 0.02
    schedule_delay = "0s"
    startup_delay = "100ms"

  [plugins."io.containerd.grpc.v1.cri"]
    device_ownership_from_security_context = false
    disable_apparmor = false
    disable_cgroup = false
    disable_hugetlb_controller = true
    disable_proc_mount = false
    disable_tcp_service = true
    enable_selinux = false
    enable_tls_streaming = false
    enable_unprivileged_icmp = false
    enable_unprivileged_ports = false
    ignore_image_defined_volumes = false
    max_concurrent_downloads = 3
    max_container_log_line_size = 16384
    netns_mounts_under_state_dir = false
    restrict_oom_score_adj = false
    sandbox_image = "registry.k8s.io/pause:3.6"
    selinux_category_range = 1024
    stats_collect_period = 10
    stream_idle_timeout = "4h0m0s"
    stream_server_address = "127.0.0.1"
    stream_server_port = "0"
    systemd_cgroup = false
    tolerate_missing_hugetlb_controller = true
    unset_seccomp_profile = ""

    [plugins."io.containerd.grpc.v1.cri".cni]
      bin_dir = "/opt/cni/bin"
      conf_dir = "/etc/cni/net.d"
      conf_template = ""
      ip_pref = ""
      max_conf_num = 1

    [plugins."io.containerd.grpc.v1.cri".containerd]
      default_runtime_name = "runc"
      disable_snapshot_annotations = true
      discard_unpacked_layers = false
      ignore_rdt_not_enabled_errors = false
      no_pivot = false
      snapshotter = "overlayfs"

      [plugins."io.containerd.grpc.v1.cri".containerd.default_runtime]
        base_runtime_spec = ""
        cni_conf_dir = ""
        cni_max_conf_num = 0
        container_annotations = []
        pod_annotations = []
        privileged_without_host_devices = false
        runtime_engine = ""
        runtime_path = ""
        runtime_root = ""
        runtime_type = ""

        [plugins."io.containerd.grpc.v1.cri".containerd.default_runtime.options]

      [plugins."io.containerd.grpc.v1.cri".containerd.runtimes]

        [plugins."io.containerd.grpc.v1.cri".containerd.runtimes.runc]
          base_runtime_spec = ""
          cni_conf_dir = ""
          cni_max_conf_num = 0
          container_annotations = []
          pod_annotations = []
          privileged_without_host_devices = false
          runtime_engine = ""
          runtime_path = ""
          runtime_root = ""
          runtime_type = "io.containerd.runc.v2"

          [plugins."io.containerd.grpc.v1.cri".containerd.runtimes.runc.options]
            BinaryName = ""
            CriuImagePath = ""
            CriuPath = ""
            CriuWorkPath = ""
            IoGid = 0
            IoUid = 0
            NoNewKeyring = false
            NoPivotRoot = false
            Root = ""
            ShimCgroup = ""
            SystemdCgroup = false

      [plugins."io.containerd.grpc.v1.cri".containerd.untrusted_workload_runtime]
        base_runtime_spec = ""
        cni_conf_dir = ""
        cni_max_conf_num = 0
        container_annotations = []
        pod_annotations = []
        privileged_without_host_devices = false
        runtime_engine = ""
        runtime_path = ""
        runtime_root = ""
        runtime_type = ""

        [plugins."io.containerd.grpc.v1.cri".containerd.untrusted_workload_runtime.options]

    [plugins."io.containerd.grpc.v1.cri".image_decryption]
      key_model = "node"

    [plugins."io.containerd.grpc.v1.cri".registry]
      config_path = ""

      [plugins."io.containerd.grpc.v1.cri".registry.auths]

      [plugins."io.containerd.grpc.v1.cri".registry.configs]

      [plugins."io.containerd.grpc.v1.cri".registry.headers]

      [plugins."io.containerd.grpc.v1.cri".registry.mirrors]

    [plugins."io.containerd.grpc.v1.cri".x509_key_pair_streaming]
      tls_cert_file = ""
      tls_key_file = ""

  [plugins."io.containerd.internal.v1.opt"]
    path = "/opt/containerd"

  [plugins."io.containerd.internal.v1.restart"]
    interval = "10s"

  [plugins."io.containerd.internal.v1.tracing"]
    sampling_ratio = 1.0
    service_name = "containerd"

  [plugins."io.containerd.metadata.v1.bolt"]
    content_sharing_policy = "shared"

  [plugins."io.containerd.monitor.v1.cgroups"]
    no_prometheus = false

  [plugins."io.containerd.runtime.v1.linux"]
    no_shim = false
    runtime = "runc"
    runtime_root = ""
    shim = "containerd-shim"
    shim_debug = false

  [plugins."io.containerd.runtime.v2.task"]
    platforms = ["linux/amd64"]
    sched_core = false

  [plugins."io.containerd.service.v1.diff-service"]
    default = ["walking"]

  [plugins."io.containerd.service.v1.tasks-service"]
    rdt_config_file = ""

  [plugins."io.containerd.snapshotter.v1.aufs"]
    root_path = ""

  [plugins."io.containerd.snapshotter.v1.btrfs"]
    root_path = ""

  [plugins."io.containerd.snapshotter.v1.devmapper"]
    async_remove = false
    base_image_size = ""
    discard_blocks = false
    fs_options = ""
    fs_type = ""
    pool_name = ""
    root_path = ""

  [plugins."io.containerd.snapshotter.v1.native"]
    root_path = ""

  [plugins."io.containerd.snapshotter.v1.overlayfs"]
    root_path = ""
    upperdir_label = false

  [plugins."io.containerd.snapshotter.v1.zfs"]
    root_path = ""

  [plugins."io.containerd.tracing.processor.v1.otlp"]
    endpoint = ""
    insecure = false
    protocol = ""

[proxy_plugins]

[stream_processors]

  [stream_processors."io.containerd.ocicrypt.decoder.v1.tar"]
    accepts = ["application/vnd.oci.image.layer.v1.tar+encrypted"]
    args = ["--decryption-keys-path", "/etc/containerd/ocicrypt/keys"]
    env = ["OCICRYPT_KEYPROVIDER_CONFIG=/etc/containerd/ocicrypt/ocicrypt_keyprovider.conf"]
    path = "ctd-decoder"
    returns = "application/vnd.oci.image.layer.v1.tar"

  [stream_processors."io.containerd.ocicrypt.decoder.v1.tar.gzip"]
    accepts = ["application/vnd.oci.image.layer.v1.tar+gzip+encrypted"]
    args = ["--decryption-keys-path", "/etc/containerd/ocicrypt/keys"]
    env = ["OCICRYPT_KEYPROVIDER_CONFIG=/etc/containerd/ocicrypt/ocicrypt_keyprovider.conf"]
    path = "ctd-decoder"
    returns = "application/vnd.oci.image.layer.v1.tar+gzip"

[timeouts]
  "io.containerd.timeout.bolt.open" = "0s"
  "io.containerd.timeout.shim.cleanup" = "5s"
  "io.containerd.timeout.shim.load" = "5s"
  "io.containerd.timeout.shim.shutdown" = "3s"
  "io.containerd.timeout.task.state" = "2s"

[ttrpc]
  address = ""
  gid = 0
  uid = 0

Once you generate the default config, you need to enable systemd cgroup for the containerd low-level container runtime, runc by changing the value of SystemdCgroup from false to true.

sudo sed -i '/SystemdCgroup/s/false/true/' /etc/containerd/config.toml

Also, as of this writing, it is recommended to use “registry.k8s.io/pause:3.9” as the CRI sandbox image. pause container image is a minimalistic container image that enables containerd to provide network isolation for pods in Kubernetes. Containerd uses pause:3.8.

grep sandbox_image /etc/containerd/config.toml

    sandbox_image = "registry.k8s.io/pause:3.8"

To change this to pause:3.9;

sudo sed -i '/pause:3.8/s/3.8/3.9/' /etc/containerd/config.toml

If the default version is other than 3.8, then adjust the number accordingly.

Verify the changes again;

grep sandbox_image /etc/containerd/config.toml

    sandbox_image = "registry.k8s.io/pause:3.9"

Start and enable containerd to run on system boot;

sudo systemctl enable --now containerd

Confirm the status;

systemctl status containerd

● containerd.service - containerd container runtime
     Loaded: loaded (/usr/lib/systemd/system/containerd.service; enabled; preset: enabled)
     Active: active (running) since Mon 2024-05-13 17:50:46 UTC; 3min 45s ago
       Docs: https://containerd.io
   Main PID: 2826 (containerd)
      Tasks: 8
     Memory: 13.5M (peak: 14.0M)
        CPU: 1.303s
     CGroup: /system.slice/containerd.service
             └─2826 /usr/bin/containerd

May 13 17:50:46 master.kifarunix.com containerd[2826]: time="2024-05-13T17:50:46.057491119Z" level=info msg="Start subscribing containerd event"
May 13 17:50:46 master.kifarunix.com containerd[2826]: time="2024-05-13T17:50:46.057526439Z" level=info msg="Start recovering state"
May 13 17:50:46 master.kifarunix.com containerd[2826]: time="2024-05-13T17:50:46.057810777Z" level=info msg="Start event monitor"
May 13 17:50:46 master.kifarunix.com containerd[2826]: time="2024-05-13T17:50:46.057825824Z" level=info msg="Start snapshots syncer"
May 13 17:50:46 master.kifarunix.com containerd[2826]: time="2024-05-13T17:50:46.057831474Z" level=info msg="Start cni network conf syncer for default"
May 13 17:50:46 master.kifarunix.com containerd[2826]: time="2024-05-13T17:50:46.057833164Z" level=info msg=serving... address=/run/containerd/containerd.sock.ttrpc
May 13 17:50:46 master.kifarunix.com containerd[2826]: time="2024-05-13T17:50:46.057840998Z" level=info msg="Start streaming server"
May 13 17:50:46 master.kifarunix.com containerd[2826]: time="2024-05-13T17:50:46.057873084Z" level=info msg=serving... address=/run/containerd/containerd.sock
May 13 17:50:46 master.kifarunix.com systemd[1]: Started containerd.service - containerd container runtime.
May 13 17:50:46 master.kifarunix.com containerd[2826]: time="2024-05-13T17:50:46.059380011Z" level=info msg="containerd successfully booted in 0.019204s"

Install Kubernetes on Ubuntu 24.04

There are a number of node components required to provide Kubernetes runtime environment that needs to be installed on each node. These include:

• kubelet: runs as an agent on each worker node and ensures that containers are running in a Pod.
• kubeadm: Bootstraps Kubernetes cluster
• kubectl: Used to run commands against Kubernetes clusters. 

These components are not available on the default Ubuntu repos. Thus, you need to install Kubernetes repos to install them.

Install Kubernetes Repository GPG Signing Key

Run the command below to install Kubernetes repo GPG key.

sudo apt install gnupg2 -y

Replace the value of the VER variable below with the release number of Kubernetes you need to run! In this guide, I will be using the current latest minor release version, v1.30.

VER=1.30

curl -fsSL https://pkgs.k8s.io/core:/stable:/v${VER}/deb/Release.key | \
sudo gpg --dearmor -o /etc/apt/trusted.gpg.d/k8s.gpg

Install Kubernetes Repository on Ubuntu 24.04

Next install the Kubernetes repository of the version matching the GPG key installed above;

echo "deb https://pkgs.k8s.io/core:/stable:/v${VER}/deb/ /" | sudo tee /etc/apt/sources.list.d/kurbenetes.list

Install Kubernetes components on all the nodes

sudo apt update

sudo apt install kubelet kubeadm kubectl -y

Mark Hold Kubernetes Packages

In order to maintain the stability of the cluster, it is important to maintain specific versions of critical packages like kubeadm, kubelet, and kubectl. This can be done by instructing the package management system (APT) to prevent those packages from being upgraded using the apt-mark hold command.

sudo apt-mark hold kubeadm kubelet kubectl

To check whether packages are on hold or not, you can use apt-mark showhold:

sudo apt-mark showhold

If you want to allow apt to upgrade these packages again, you can remove the hold using apt-mark unhold:

sudo apt-mark unhold kubeadm kubelet kubectl

Initialize Kubernetes Cluster on Control Plane using Kubeadm

Once the above steps are completed, initialize the Kubernetes cluster on the master node. The Kubernetes master is responsible for maintaining the desired state for your cluster.

We will be using kubeadm tool to deploy our K8S cluster.

The cluster can be initiated using the kubeadm tool by passing the init command argument;

kubeadm init <args>

Some of the common arguments/options include;

• –apiserver-advertise-address: Defines the IP address the API Server will listen on. If not set the default network interface will be used. An example usage is --apiserver-advertise-address=192.168.122.60.
• –pod-network-cidr: Specify range of IP addresses for the pod network. If set, the control plane will automatically allocate CIDRs for every node. You use this to define your preferred network range if there is a chance for collision between your network plugin’s preferred Pod network addon and some of your host networks to happen e.g--pod-network-cidr=10.100.0.0/16.
• –control-plane-endpoint: Specifies the hostname and port that the API server will listen on. This is recommended over the use of --apiserver-advertise-address because it enables you to define a shared endpoint such as load balance DNS name or an IP address that can be used when you upgrade single master node to highly available node. For example, --control-plane-endpoint=cluster.kifarunix-demo.com:6443.

Since we are just running a single master node Kubernetes cluster in this guide (for demo purposes), with no plans to upgrade to highly available cluster, then we will specify just the IP address of the control plane while bootstrapping our cluster.

Thus, run the command below on the master node to bootstrap the Kubernetes control-plane node.

sudo kubeadm init --apiserver-advertise-address=192.168.122.60 --pod-network-cidr=10.100.0.0/16

The command will start by pre-pulling (kubeadm config images pull) the required container images for a Kubernetes cluster before initializing the cluster.

Once the initialization is done, you should be able to see an output similar to the one below;

[init] Using Kubernetes version: v1.30.0
[preflight] Running pre-flight checks
[preflight] Pulling images required for setting up a Kubernetes cluster
[preflight] This might take a minute or two, depending on the speed of your internet connection
[preflight] You can also perform this action in beforehand using 'kubeadm config images pull'
[certs] Using certificateDir folder "/etc/kubernetes/pki"
[certs] Generating "ca" certificate and key
[certs] Generating "apiserver" certificate and key
[certs] apiserver serving cert is signed for DNS names [kubernetes kubernetes.default kubernetes.default.svc kubernetes.default.svc.cluster.local master.kifarunix.com] and IPs [10.96.0.1 192.168.122.60]
[certs] Generating "apiserver-kubelet-client" certificate and key
[certs] Generating "front-proxy-ca" certificate and key
[certs] Generating "front-proxy-client" certificate and key
[certs] Generating "etcd/ca" certificate and key
[certs] Generating "etcd/server" certificate and key
[certs] etcd/server serving cert is signed for DNS names [localhost master.kifarunix.com] and IPs [192.168.122.60 127.0.0.1 ::1]
[certs] Generating "etcd/peer" certificate and key
[certs] etcd/peer serving cert is signed for DNS names [localhost master.kifarunix.com] and IPs [192.168.122.60 127.0.0.1 ::1]
[certs] Generating "etcd/healthcheck-client" certificate and key
[certs] Generating "apiserver-etcd-client" certificate and key
[certs] Generating "sa" key and public key
[kubeconfig] Using kubeconfig folder "/etc/kubernetes"
[kubeconfig] Writing "admin.conf" kubeconfig file
[kubeconfig] Writing "super-admin.conf" kubeconfig file
[kubeconfig] Writing "kubelet.conf" kubeconfig file
[kubeconfig] Writing "controller-manager.conf" kubeconfig file
[kubeconfig] Writing "scheduler.conf" kubeconfig file
[etcd] Creating static Pod manifest for local etcd in "/etc/kubernetes/manifests"
[control-plane] Using manifest folder "/etc/kubernetes/manifests"
[control-plane] Creating static Pod manifest for "kube-apiserver"
[control-plane] Creating static Pod manifest for "kube-controller-manager"
[control-plane] Creating static Pod manifest for "kube-scheduler"
[kubelet-start] Writing kubelet environment file with flags to file "/var/lib/kubelet/kubeadm-flags.env"
[kubelet-start] Writing kubelet configuration to file "/var/lib/kubelet/config.yaml"
[kubelet-start] Starting the kubelet
[wait-control-plane] Waiting for the kubelet to boot up the control plane as static Pods from directory "/etc/kubernetes/manifests"
[kubelet-check] Waiting for a healthy kubelet. This can take up to 4m0s
[kubelet-check] The kubelet is healthy after 501.313365ms
[api-check] Waiting for a healthy API server. This can take up to 4m0s
[api-check] The API server is healthy after 4.003829486s
[upload-config] Storing the configuration used in ConfigMap "kubeadm-config" in the "kube-system" Namespace
[kubelet] Creating a ConfigMap "kubelet-config" in namespace kube-system with the configuration for the kubelets in the cluster
[upload-certs] Skipping phase. Please see --upload-certs
[mark-control-plane] Marking the node master.kifarunix.com as control-plane by adding the labels: [node-role.kubernetes.io/control-plane node.kubernetes.io/exclude-from-external-load-balancers]
[mark-control-plane] Marking the node master.kifarunix.com as control-plane by adding the taints [node-role.kubernetes.io/control-plane:NoSchedule]
[bootstrap-token] Using token: 2ntlip.lsw3yriy62bs16pp
[bootstrap-token] Configuring bootstrap tokens, cluster-info ConfigMap, RBAC Roles
[bootstrap-token] Configured RBAC rules to allow Node Bootstrap tokens to get nodes
[bootstrap-token] Configured RBAC rules to allow Node Bootstrap tokens to post CSRs in order for nodes to get long term certificate credentials
[bootstrap-token] Configured RBAC rules to allow the csrapprover controller automatically approve CSRs from a Node Bootstrap Token
[bootstrap-token] Configured RBAC rules to allow certificate rotation for all node client certificates in the cluster
[bootstrap-token] Creating the "cluster-info" ConfigMap in the "kube-public" namespace
[kubelet-finalize] Updating "/etc/kubernetes/kubelet.conf" to point to a rotatable kubelet client certificate and key
[addons] Applied essential addon: CoreDNS
[addons] Applied essential addon: kube-proxy

Your Kubernetes control-plane has initialized successfully!

To start using your cluster, you need to run the following as a regular user:

  mkdir -p $HOME/.kube
  sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
  sudo chown $(id -u):$(id -g) $HOME/.kube/config

Alternatively, if you are the root user, you can run:

  export KUBECONFIG=/etc/kubernetes/admin.conf

You should now deploy a pod network to the cluster.
Run "kubectl apply -f [podnetwork].yaml" with one of the options listed at:
  https://kubernetes.io/docs/concepts/cluster-administration/addons/

Then you can join any number of worker nodes by running the following on each as root:

kubeadm join 192.168.122.60:6443 --token 2ntlip.lsw3yriy62bs16pp \
	--discovery-token-ca-cert-hash sha256:a22e5b78b50c54af7de5390ec804b311d28ea40048d9c6b66ee21660bbe4d212

As suggested on the output above, you need to run the commands provided on the master node to start using your cluster.

Be sure to run the commands as regular user (recommended), with sudo rights.

Thus, if you are root, then switch to regular user with sudo rights (kifarunix is our regular, it could be a different user for you)

su - kifarunix

Next, create a Kubernetes cluster directory.

mkdir -p $HOME/.kube

Copy Kubernetes admin configuration file to the cluster directory created above.

sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config

Set the proper ownership for the cluster configuration file.

sudo chown $(id -u):$(id -g) $HOME/.kube/config

Verify the status of the Kubernetes cluster;

kubectl get nodes

NAME                   STATUS     ROLES           AGE     VERSION
master.kifarunix.com   NotReady   control-plane   8m14s   v1.30.0

As you can see, the cluster is not ready yet.

You can also get the address of the control plane and cluster services;

kubectl cluster-info

Kubernetes control plane is running at https://192.168.122.60:6443
CoreDNS is running at https://192.168.122.60:6443/api/v1/namespaces/kube-system/services/kube-dns:dns/proxy

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

Install Pod Network Addon on Master Node

A Pod is a group of one or more related containers in a Kubernetes cluster. They share the same lifecycle, storage/network. For Pods to communicate with one another, you must deploy a Container Network Interface (CNI) based Pod network add-on.

There are multiple Pod network addons that you can choose from. Refer to Addons page for more information.

To deploy a CNI Pod network, run the command below on the master node;

kubectl apply -f [podnetwork].yaml

Where [podnetwork].yaml is the path to your preferred CNI YAML file. In this demo, we will use Calico network plugin.

Install Calico Pod network addon Operator by running the command below. Execute the command as the user with which you created the Kubernetes cluster.

Current release version is v3.28.0.

Get the current release version from releases page and replace the value of CNI_VER below.

CNI_VER=3.28.0

kubectl create -f https://raw.githubusercontent.com/projectcalico/calico/v${CNI_VER}/manifests/tigera-operator.yaml

namespace/tigera-operator created
customresourcedefinition.apiextensions.k8s.io/bgpconfigurations.crd.projectcalico.org created
customresourcedefinition.apiextensions.k8s.io/bgpfilters.crd.projectcalico.org created
customresourcedefinition.apiextensions.k8s.io/bgppeers.crd.projectcalico.org created
customresourcedefinition.apiextensions.k8s.io/blockaffinities.crd.projectcalico.org created
customresourcedefinition.apiextensions.k8s.io/caliconodestatuses.crd.projectcalico.org created
customresourcedefinition.apiextensions.k8s.io/clusterinformations.crd.projectcalico.org created
customresourcedefinition.apiextensions.k8s.io/felixconfigurations.crd.projectcalico.org created
customresourcedefinition.apiextensions.k8s.io/globalnetworkpolicies.crd.projectcalico.org created
customresourcedefinition.apiextensions.k8s.io/globalnetworksets.crd.projectcalico.org created
customresourcedefinition.apiextensions.k8s.io/hostendpoints.crd.projectcalico.org created
customresourcedefinition.apiextensions.k8s.io/ipamblocks.crd.projectcalico.org created
customresourcedefinition.apiextensions.k8s.io/ipamconfigs.crd.projectcalico.org created
customresourcedefinition.apiextensions.k8s.io/ipamhandles.crd.projectcalico.org created
customresourcedefinition.apiextensions.k8s.io/ippools.crd.projectcalico.org created
customresourcedefinition.apiextensions.k8s.io/ipreservations.crd.projectcalico.org created
customresourcedefinition.apiextensions.k8s.io/kubecontrollersconfigurations.crd.projectcalico.org created
customresourcedefinition.apiextensions.k8s.io/networkpolicies.crd.projectcalico.org created
customresourcedefinition.apiextensions.k8s.io/networksets.crd.projectcalico.org created
customresourcedefinition.apiextensions.k8s.io/apiservers.operator.tigera.io created
customresourcedefinition.apiextensions.k8s.io/imagesets.operator.tigera.io created
customresourcedefinition.apiextensions.k8s.io/installations.operator.tigera.io created
customresourcedefinition.apiextensions.k8s.io/tigerastatuses.operator.tigera.io created
serviceaccount/tigera-operator created
clusterrole.rbac.authorization.k8s.io/tigera-operator created
clusterrolebinding.rbac.authorization.k8s.io/tigera-operator created
deployment.apps/tigera-operator created

Next, download the custom resources necessary to configure Calico. The default network for Calico plugin is 192.168.0.0/16. If you used custom pod CIDR as defined above (–pod-network-cidr=10.100.0.0/16), download the custom resource file and modify the network to match your custom one.

We will the manifest of the same version of CNI above.

wget https://raw.githubusercontent.com/projectcalico/calico/v${CNI_VER}/manifests/custom-resources.yaml

cat custom-resources.yaml

# This section includes base Calico installation configuration.
# For more information, see: https://docs.tigera.io/calico/latest/reference/installation/api#operator.tigera.io/v1.Installation
apiVersion: operator.tigera.io/v1
kind: Installation
metadata:
  name: default
spec:
  # Configures Calico networking.
  calicoNetwork:
    ipPools:
    - name: default-ipv4-ippool
      blockSize: 26
      cidr: 192.168.0.0/16
      encapsulation: VXLANCrossSubnet
      natOutgoing: Enabled
      nodeSelector: all()

---

# This section configures the Calico API server.
# For more information, see: https://docs.tigera.io/calico/latest/reference/installation/api#operator.tigera.io/v1.APIServer
apiVersion: operator.tigera.io/v1
kind: APIServer
metadata:
  name: default
spec: {}

The network section of the custom resource file will now look like below by default;

    - blockSize: 26
      cidr: 192.168.0.0/16

Update the network subnet to match your subnet.

sed -i 's/192.168/10.100/' custom-resources.yaml

Apply the changes

kubectl create -f custom-resources.yaml

Sample output;

installation.operator.tigera.io/default created
apiserver.operator.tigera.io/default created

Get Running Pods in the Kubernetes cluster

Once the command completes, you can list the Pods in the namespaces by running the command below;

kubectl get pods --all-namespaces

NAMESPACE         NAME                                           READY   STATUS              RESTARTS   AGE
calico-system     calico-kube-controllers-795f68c999-xg8l6       0/1     ContainerCreating   0          31s
calico-system     calico-node-phgxz                              0/1     Running             0          24s
calico-system     calico-typha-5c68d5959d-kkxwc                  1/1     Terminating         0          32s
calico-system     calico-typha-5ff5999dc9-vr2q9                  0/1     Pending             0          31s
calico-system     csi-node-driver-fjxfd                          0/2     ContainerCreating   0          32s
kube-system       coredns-7db6d8ff4d-762fg                       0/1     Running             0          24m
kube-system       coredns-7db6d8ff4d-flnrq                       0/1     Running             0          24m
kube-system       etcd-master.kifarunix.com                      1/1     Running             2          24m
kube-system       kube-apiserver-master.kifarunix.com            1/1     Running             2          24m
kube-system       kube-controller-manager-master.kifarunix.com   1/1     Running             2          24m
kube-system       kube-proxy-jv9x9                               1/1     Running             0          24m
kube-system       kube-scheduler-master.kifarunix.com            1/1     Running             2          24m
tigera-operator   tigera-operator-7d5cd7fcc8-7bw5j               1/1     Running             0          12m

You can list Pods on specific namespaces;

kubectl get pods -n calico-system

NAMESPACE         NAME                                           READY   STATUS              RESTARTS   AGE
calico-system     calico-kube-controllers-795f68c999-xg8l6       0/1     ContainerCreating   0          31s
calico-system     calico-node-phgxz                              0/1     Running             0          24s
calico-system     calico-typha-5c68d5959d-kkxwc                  1/1     Terminating         0          32s
calico-system     calico-typha-5ff5999dc9-vr2q9                  0/1     Pending             0          31s
calico-system     csi-node-driver-fjxfd                          0/2     ContainerCreating   0          32s

As can be seen, all Pods on calico-system namespace are running.

Open Kubernetes Cluster Ports on Firewall

If firewall is running on the nodes, then there are some ports that needs to be opened on the firewall;

Control Plane ports;

So the ports that should be open and accessible from outside the node are:

• 6443 – Kubernetes API Server (secure port)
• 2379-2380 – etcd server client API
• 10250 – Kubelet API
• 10251 – kube-scheduler
• 10252 – kube-controller-manager

In my setup, I am using UFW. Hence, you only need to open the ports below on Master/Control Plane;

for i in 6443 2379:2380 10250:10252; do sudo ufw allow from any to any port $i proto tcp; done

You can restrict access to the API from specific networks/IPS.

Worker Nodes;

On each Woker node, open the Kubelete API port;

ufw allow from any to any port 10250 proto tcp comment "Open Kubelet API port"

You can restrict access to the API from specific networks/IPs.

Add Worker Nodes to Kubernetes Cluster

You can now add Worker nodes to the Kubernetes cluster using the kubeadm join command as follows.

Before that, ensure that container runtime is installed, configured and running. We are using containerd CRI;

systemctl status containerd

Sample output from worker01 node;

● containerd.service - containerd container runtime
     Loaded: loaded (/usr/lib/systemd/system/containerd.service; enabled; preset: enabled)
     Active: active (running) since Mon 2024-05-13 20:38:59 UTC; 20h ago
       Docs: https://containerd.io
    Process: 4430 ExecStartPre=/sbin/modprobe overlay (code=exited, status=0/SUCCESS)
   Main PID: 4432 (containerd)
      Tasks: 8
     Memory: 13.4M (peak: 13.9M)
        CPU: 1min 45.227s
     CGroup: /system.slice/containerd.service
             └─4432 /usr/bin/containerd

May 13 20:38:59 wk01.kifarunix.com containerd[4432]: time="2024-05-13T20:38:59.786586300Z" level=info msg="Start subscribing containerd event"
May 13 20:38:59 wk01.kifarunix.com containerd[4432]: time="2024-05-13T20:38:59.786651551Z" level=info msg="Start recovering state"
May 13 20:38:59 wk01.kifarunix.com containerd[4432]: time="2024-05-13T20:38:59.786806494Z" level=info msg=serving... address=/run/containerd/containerd.sock.ttrpc
May 13 20:38:59 wk01.kifarunix.com containerd[4432]: time="2024-05-13T20:38:59.786874950Z" level=info msg="Start event monitor"
May 13 20:38:59 wk01.kifarunix.com containerd[4432]: time="2024-05-13T20:38:59.786931542Z" level=info msg="Start snapshots syncer"
May 13 20:38:59 wk01.kifarunix.com containerd[4432]: time="2024-05-13T20:38:59.786886363Z" level=info msg=serving... address=/run/containerd/containerd.sock
May 13 20:38:59 wk01.kifarunix.com containerd[4432]: time="2024-05-13T20:38:59.786971950Z" level=info msg="Start cni network conf syncer for default"
May 13 20:38:59 wk01.kifarunix.com containerd[4432]: time="2024-05-13T20:38:59.787003012Z" level=info msg="Start streaming server"
May 13 20:38:59 wk01.kifarunix.com containerd[4432]: time="2024-05-13T20:38:59.787040271Z" level=info msg="containerd successfully booted in 0.021146s"
May 13 20:38:59 wk01.kifarunix.com systemd[1]: Started containerd.service - containerd container runtime.

Once you have confirmed that, get the cluster join command that was output during cluster boot strapping and execute on each node.

Note that this command is displayed after initializing the control plane above and it should be executed as root user.

sudo kubeadm join 192.168.122.60:6443 \
	--token 2ntlip.lsw3yriy62bs16pp \
	--discovery-token-ca-cert-hash sha256:a22e5b78b50c54af7de5390ec804b311d28ea40048d9c6b66ee21660bbe4d212

If you didn’t save the Kubernetes Cluster joining command, you can at any given time print using the command below on the Master or control plane;

kubeadm token create --print-join-command

Once the command runs, you will get an output similar to below;

[preflight] Running pre-flight checks
[preflight] Reading configuration from the cluster...
[preflight] FYI: You can look at this config file with 'kubectl -n kube-system get cm kubeadm-config -o yaml'
[kubelet-start] Writing kubelet configuration to file "/var/lib/kubelet/config.yaml"
[kubelet-start] Writing kubelet environment file with flags to file "/var/lib/kubelet/kubeadm-flags.env"
[kubelet-start] Starting the kubelet
[kubelet-check] Waiting for a healthy kubelet. This can take up to 4m0s
[kubelet-check] The kubelet is healthy after 501.461586ms
[kubelet-start] Waiting for the kubelet to perform the TLS Bootstrap

This node has joined the cluster:
* Certificate signing request was sent to apiserver and a response was received.
* The Kubelet was informed of the new secure connection details.

Run 'kubectl get nodes' on the control-plane to see this node join the cluster.

On the Kubernetes control plane (master, as the regular user with which you created the cluster as), run the command below to verify that the nodes have joined the cluster.

kubectl get nodes

NAME                   STATUS     ROLES           AGE    VERSION
master.kifarunix.com   Ready      control-plane   20h    v1.30.0
wk01.kifarunix.com     Ready                107s   v1.30.0
wk02.kifarunix.com     NotReady             11s    v1.30.0
wk03.kifarunix.com     NotReady             6s     v1.30.0

There are different node stati;

1. NotReady: The node has been added to the cluster but is not yet ready to accept workloads.
2. SchedulingDisabled: The node is not able to receive new workloads because it is marked as unschedulable.
3. Ready: The node is ready to accept workloads.
4. OutOfDisk: Indicates that the node is running out of disk space.
5. MemoryPressure: Indicates that the node is running out of memory.
6. PIDPressure: indicates that there are too many processes on the node
7. DiskPressure: Indicates that the node is running out of disk space.
8. NetworkUnavailable: Indicates that the node is not reachable via the network.
9. Unschedulable: Indicates that the node is not schedulable for new workloads.
10. ConditionUnknown: Indicates that the node status is unknown due to an error.

Role of the Worker nodes may show up as <none>. This is okay. No role is assigned to the node by default. It is only until the control plane assign a workload on the node then it shows up the correct role.

You can however update this ROLE using the command;

kubectl label node <worker-node-name> node-role.kubernetes.io/worker=true

Get Kubernetes Cluster Information

As you can see, we now have a cluster. Run the command below to get cluster information.

kubectl cluster-info

Kubernetes control plane is running at https://192.168.122.60:6443
CoreDNS is running at https://192.168.122.60:6443/api/v1/namespaces/kube-system/services/kube-dns:dns/proxy

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

List Kubernetes Cluster API Resources

You can list all Kubernetes cluster resources using the command below;

kubectl api-resources

NAME                                SHORTNAMES   APIVERSION                        NAMESPACED   KIND
bindings                                         v1                                true         Binding
componentstatuses                   cs           v1                                false        ComponentStatus
configmaps                          cm           v1                                true         ConfigMap
endpoints                           ep           v1                                true         Endpoints
events                              ev           v1                                true         Event
limitranges                         limits       v1                                true         LimitRange
namespaces                          ns           v1                                false        Namespace
nodes                               no           v1                                false        Node
persistentvolumeclaims              pvc          v1                                true         PersistentVolumeClaim
persistentvolumes                   pv           v1                                false        PersistentVolume
pods                                po           v1                                true         Pod
podtemplates                                     v1                                true         PodTemplate
replicationcontrollers              rc           v1                                true         ReplicationController
resourcequotas                      quota        v1                                true         ResourceQuota
secrets                                          v1                                true         Secret
serviceaccounts                     sa           v1                                true         ServiceAccount
services                            svc          v1                                true         Service
mutatingwebhookconfigurations                    admissionregistration.k8s.io/v1   false        MutatingWebhookConfiguration
validatingadmissionpolicies                      admissionregistration.k8s.io/v1   false        ValidatingAdmissionPolicy
validatingadmissionpolicybindings                admissionregistration.k8s.io/v1   false        ValidatingAdmissionPolicyBinding
validatingwebhookconfigurations                  admissionregistration.k8s.io/v1   false        ValidatingWebhookConfiguration
customresourcedefinitions           crd,crds     apiextensions.k8s.io/v1           false        CustomResourceDefinition
apiservices                                      apiregistration.k8s.io/v1         false        APIService
controllerrevisions                              apps/v1                           true         ControllerRevision
daemonsets                          ds           apps/v1                           true         DaemonSet
deployments                         deploy       apps/v1                           true         Deployment
replicasets                         rs           apps/v1                           true         ReplicaSet
statefulsets                        sts          apps/v1                           true         StatefulSet
selfsubjectreviews                               authentication.k8s.io/v1          false        SelfSubjectReview
tokenreviews                                     authentication.k8s.io/v1          false        TokenReview
localsubjectaccessreviews                        authorization.k8s.io/v1           true         LocalSubjectAccessReview
selfsubjectaccessreviews                         authorization.k8s.io/v1           false        SelfSubjectAccessReview
selfsubjectrulesreviews                          authorization.k8s.io/v1           false        SelfSubjectRulesReview
subjectaccessreviews                             authorization.k8s.io/v1           false        SubjectAccessReview
horizontalpodautoscalers            hpa          autoscaling/v2                    true         HorizontalPodAutoscaler
cronjobs                            cj           batch/v1                          true         CronJob
jobs                                             batch/v1                          true         Job
certificatesigningrequests          csr          certificates.k8s.io/v1            false        CertificateSigningRequest
leases                                           coordination.k8s.io/v1            true         Lease
bgpconfigurations                                crd.projectcalico.org/v1          false        BGPConfiguration
bgpfilters                                       crd.projectcalico.org/v1          false        BGPFilter
bgppeers                                         crd.projectcalico.org/v1          false        BGPPeer
blockaffinities                                  crd.projectcalico.org/v1          false        BlockAffinity
caliconodestatuses                               crd.projectcalico.org/v1          false        CalicoNodeStatus
clusterinformations                              crd.projectcalico.org/v1          false        ClusterInformation
felixconfigurations                              crd.projectcalico.org/v1          false        FelixConfiguration
globalnetworkpolicies                            crd.projectcalico.org/v1          false        GlobalNetworkPolicy
globalnetworksets                                crd.projectcalico.org/v1          false        GlobalNetworkSet
hostendpoints                                    crd.projectcalico.org/v1          false        HostEndpoint
ipamblocks                                       crd.projectcalico.org/v1          false        IPAMBlock
ipamconfigs                                      crd.projectcalico.org/v1          false        IPAMConfig
ipamhandles                                      crd.projectcalico.org/v1          false        IPAMHandle
ippools                                          crd.projectcalico.org/v1          false        IPPool
ipreservations                                   crd.projectcalico.org/v1          false        IPReservation
kubecontrollersconfigurations                    crd.projectcalico.org/v1          false        KubeControllersConfiguration
networkpolicies                                  crd.projectcalico.org/v1          true         NetworkPolicy
networksets                                      crd.projectcalico.org/v1          true         NetworkSet
endpointslices                                   discovery.k8s.io/v1               true         EndpointSlice
events                              ev           events.k8s.io/v1                  true         Event
flowschemas                                      flowcontrol.apiserver.k8s.io/v1   false        FlowSchema
prioritylevelconfigurations                      flowcontrol.apiserver.k8s.io/v1   false        PriorityLevelConfiguration
ingressclasses                                   networking.k8s.io/v1              false        IngressClass
ingresses                           ing          networking.k8s.io/v1              true         Ingress
networkpolicies                     netpol       networking.k8s.io/v1              true         NetworkPolicy
runtimeclasses                                   node.k8s.io/v1                    false        RuntimeClass
apiservers                                       operator.tigera.io/v1             false        APIServer
imagesets                                        operator.tigera.io/v1             false        ImageSet
installations                                    operator.tigera.io/v1             false        Installation
tigerastatuses                                   operator.tigera.io/v1             false        TigeraStatus
poddisruptionbudgets                pdb          policy/v1                         true         PodDisruptionBudget
clusterrolebindings                              rbac.authorization.k8s.io/v1      false        ClusterRoleBinding
clusterroles                                     rbac.authorization.k8s.io/v1      false        ClusterRole
rolebindings                                     rbac.authorization.k8s.io/v1      true         RoleBinding
roles                                            rbac.authorization.k8s.io/v1      true         Role
priorityclasses                     pc           scheduling.k8s.io/v1              false        PriorityClass
csidrivers                                       storage.k8s.io/v1                 false        CSIDriver
csinodes                                         storage.k8s.io/v1                 false        CSINode
csistoragecapacities                             storage.k8s.io/v1                 true         CSIStorageCapacity
storageclasses                      sc           storage.k8s.io/v1                 false        StorageClass
volumeattachments                                storage.k8s.io/v1                 false        VolumeAttachment

You are now ready to deploy an application on Kubernetes cluster.

Want to dive deeper in getting Kubernetes up and running? Check out this book, Kubernetes: Up and Running: Dive into the Future of Infrastructure 3rd Edition by Brendan Burns.

Remove Worker Nodes from Cluster

You can gracefully remove a node from Kubernetes cluster as described in the guide below;

Gracefully Remove Worker Node from Kubernetes Cluster

AppArmor Blocks runc Signals, Pods Stuck Terminating

You might have realized that in the recent version of Ubuntu, there is an issue whereby draining the nodes or deleting the pods get stuck with such errors in apparmor logs as;

2024-06-14T19:04:43.331091+00:00 worker-01 kernel: audit: type=1400 audit(1718391883.329:221): apparmor="DENIED" operation="signal" class="signal" profile="cri-containerd.apparmor.d" pid=7445 comm="runc" requested_mask="receive" denied_mask="receive" signal=kill peer="runc

This is a bug on AppArmor profile that denies signals from runc. This results in many pods being stuck in a terminating state. The bug was reported by Sebastian Podjasek on 2024-05-10. It affects Ubuntu containerd-app package.

Read how to fix on kubectl drain node gets stuck forever [Apparmor Bug]

Install Kubernetes Dashboard

You can manage your cluster from the dashboard using Kubernetes. See the guide below;

How to Install Kubernetes Dashboard

Further Reading

Getting Started with Kubernetes