There are many tools out there to provision single-node Kubernetes clusters, but kubeadm is the way to go for a production-like set-up. Although it is more difficult to create a cluster with kubeadm, you can tweak the cluster to your needs with its configuration options. Following this post, you can easily create a Single-node Kubernetes Cluster using kubeadm on Ubuntu 22.04.
Install general dependencies
You need to install packages on your system for the commands we will use later.
sudo apt-get update
sudo apt-get install -y apt-transport-https ca-certificates curl
Install containerd
Although we have a few container runtimes to choose from, we’re going with containerd. Before we install containerd, we’ll create its configuration file.
curl -fsSLo containerd-config.toml \
https://gist.githubusercontent.com/oradwell/31ef858de3ca43addef68ff971f459c2/raw/5099df007eb717a11825c3890a0517892fa12dbf/containerd-config.toml
sudo mkdir /etc/containerd
sudo mv containerd-config.toml /etc/containerd/config.toml
Without delay, you can install containerd from their official GitHub repository as recommended using the following commands:
curl -fLo containerd-1.6.14-linux-amd64.tar.gz \ https://github.com/containerd/containerd/releases/download/v1.6.14/containerd-1.6.14-linux-amd64.tar.gz # Extract the binaries sudo tar Cxzvf /usr/local containerd-1.6.14-linux-amd64.tar.gz # Install containerd as a service sudo curl -fsSLo /etc/systemd/system/containerd.service \ https://raw.githubusercontent.com/containerd/containerd/main/containerd.service sudo systemctl daemon-reload sudo systemctl enable --now containerd
Install runc
Installing runc from their official GitHub repository is the recommended way.
curl -fsSLo runc.amd64 \
https://github.com/opencontainers/runc/releases/download/v1.1.3/runc.amd64
sudo install -m 755 runc.amd64 /usr/local/sbin/runc
Install CNI network plugins
Install Container Network Interface network plugins from their official GitHub repository.
curl -fLo cni-plugins-linux-amd64-v1.1.1.tgz \ https://github.com/containernetworking/plugins/releases/download/v1.1.1/cni-plugins-linux-amd64-v1.1.1.tgz sudo mkdir -p /opt/cni/bin sudo tar Cxzvf /opt/cni/bin cni-plugins-linux-amd64-v1.1.1.tgz
Forward IPv4 and let iptables see bridged network traffic
You need to enable overlay and br_netfilter kernel modules. Additionally, you need to allow iptables see bridged network traffic.
cat <<EOF | sudo tee /etc/modules-load.d/k8s.conf
overlay
br_netfilter
EOF
sudo modprobe -a overlay br_netfilter
# sysctl params required by setup, params persist across reboots
cat <<EOF | sudo tee /etc/sysctl.d/k8s.conf
net.bridge.bridge-nf-call-iptables = 1
net.bridge.bridge-nf-call-ip6tables = 1
net.ipv4.ip_forward = 1
EOF
# Apply sysctl params without reboot
sudo sysctl --system
Install kubeadm, kubelet & kubectl
You need to ensure the versions of kubeadm, kubelet and kubectl are compatible.
# Add Kubernetes GPG key curl -fsSL https://packages.cloud.google.com/apt/doc/apt-key.gpg | sudo gpg --dearmor -o /etc/apt/keyrings/kubernetes-archive-keyring.gpg # Add Kubernetes apt repository echo "deb [signed-by=/etc/apt/keyrings/kubernetes-archive-keyring.gpg] https://apt.kubernetes.io/ kubernetes-xenial main" | sudo tee /etc/apt/sources.list.d/kubernetes.list # Fetch package list sudo apt-get update sudo apt-get install -y kubelet kubeadm kubectl # Prevent them from being updated automatically sudo apt-mark hold kubelet kubeadm kubectl
Ensure swap is disabled
You have to disable the swap feature because Kubernetes does not support it. See the GitHub issue regarding swap on Kubernetes for details.
# See if swap is enabled
swapon --show
# Turn off swap
sudo swapoff -a
# Disable swap completely
sudo sed -i -e '/swap/d' /etc/fstab
Create the cluster using kubeadm
It’s only a single command to initialise the cluster, but it won’t be very functional in single-node environments until we make some changes. Note that we’re providing “–pod-network-cidr” parameter as required by our CNI plugin (Flannel).
sudo kubeadm init --pod-network-cidr=10.244.0.0/16
Configure kubectl
To access the cluster, we have to configure kubectl.
mkdir -p $HOME/.kube
sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
sudo chown $(id -u):$(id -g) $HOME/.kube/config
Untaint node
We must untaint the node to allow pods to be deployed to our single-node cluster. Otherwise, your pods will be stuck in a pending state.
kubectl taint nodes --all node-role.kubernetes.io/master-
kubectl taint nodes --all node-role.kubernetes.io/control-plane-
Install a CNI plugin
For networking to function, you must install a Container Network Interface (CNI) plugin. With this in mind, we’re installing flannel.
kubectl apply -f https://raw.githubusercontent.com/coreos/flannel/master/Documentation/kube-flannel.ymlInstall helm
To install our packages, we’re installing helm v3.
curl https://raw.githubusercontent.com/helm/helm/master/scripts/get-helm-3 | bashInstall a CSI driver
We need to install a Container Storage Interface (CSI) driver for the storage to work. We’ll install OpenEBS.
# Add openebs repo to helmhelm repo add openebs https://openebs.github.io/charts
kubectl create namespace openebshelm--namespace=openebsinstall openebs openebs/openebs
Install a test application
To test the cluster, you can deploy WordPress. Note that we need to specify the storage class provided by our CSI.
# Add bitnami repo to helmhelm repo add bitnami https://charts.bitnami.com/bitnami
helm install wordpress bitnami/wordpress \
--set=global.storageClass=openebs-hostpath
We’ve just provisioned a cluster using kubeadm on Ubuntu 22.04!
You have successfully created a single-node Kubernetes Cluster using kubeadm on Ubuntu 22.04, and the cluster has everything you need to install your application.
If you’d like to watch this in a video, see below:
References
- Installing kubeadm | Kubernetes
- Creating a cluster with kubeadm | Kubernetes
- Container runtimes | Kubernetes
- Get started with containerd
- Disable swap on Ubuntu – Grasping Tech
- Kubernetes: Up and Running – 2nd Edition – Amazon
Dear Oliver,
thanks for this wonderful detailed instructions, it helped me very much.
There was one problem with the “containerd” version 1.5.13. This versions produced an error when doing `kubeadm init`. This installs Kubernetes 1.26.
`Starting with kubernetes 1.26, containerd 1.5.9 is out of support [0]`
see https://containerd.io/releases/#kubernetes-support
The solution was to install the latest version (1.6.14) of containerd:
“`
curl -fsSLo containerd-1.6.14-linux-amd64.tar.gz https://github.com/containerd/containerd/releases/download/v1.6.14/containerd-1.6.14-linux-amd64.tar.gz
# Extract the binaries
sudo tar Cxzvf /usr/local containerd-1.6.14-linux-amd64.tar.gz
“`
When exchanging these three lines in the above description the installation was successfull.
Thanks, feri
Hi Feri,
I’ve just updated the containerd version in the post.
Thanks for your feedback.
Thanks
Oliver
I am getting this error at the taint level
kubectl taint nodes –all node-role.kubernetes.io/master-
error: taint “node-role.kubernetes.io/master” not found
this command worked fine
kubectl taint nodes –all node-role.kubernetes.io/control-plane-
any ideas?
that’s fine to ignore. The “master” taint was removed in favour of the “control-plane” taint
Great article, thanks. I added the following to streamline my containerd setup:
sudo crictl config runtime-endpoint unix:///var/run/containerd/containerd.sock
sudo crictl config image-endpoint unix:///var/run/containerd/containerd.sock
This appears to be not working on an Ubuntu 22.04 EC2 instance (us-west):
sudo kubeadm init –pod-network-cidr=10.244.0.0/16 –image-repository=k8s.gcr.io
[init] Using Kubernetes version: v1.26.1
[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’
error execution phase preflight: [preflight] Some fatal errors occurred:
[ERROR ImagePull]: failed to pull image k8s.gcr.io/coredns:v1.9.3: output: E0128 18:45:39.311321 3099 remote_image.go:171] “PullImage from image service failed” err=”rpc error: code = NotFound desc = failed to pull and unpack image \”k8s.gcr.io/coredns:v1.9.3\”: failed to resolve reference \”k8s.gcr.io/coredns:v1.9.3\”: k8s.gcr.io/coredns:v1.9.3: not found” image=”k8s.gcr.io/coredns:v1.9.3″
time=”2023-01-28T18:45:39Z” level=fatal msg=”pulling image: rpc error: code = NotFound desc = failed to pull and unpack image \”k8s.gcr.io/coredns:v1.9.3\”: failed to resolve reference \”k8s.gcr.io/coredns:v1.9.3\”: k8s.gcr.io/coredns:v1.9.3: not found”
, error: exit status 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
With default image-repository, all image-pulls are failing.
Looks like the URL for the container image has changed.
This may help: https://github.com/kubernetes/kubernetes/issues/112131
thank you!
Fantastic
Great job
Well done
hi Oliver
I got below messages during installation. I followed the steps in this url. Please let me know if I am missing anything
kubectl apply -f https://raw.githubusercontent.com/coreos/flannel/master/Documentation/kube-flannel.yml
The connection to the server localhost:8080 was refused – did you specify the right host or port?
It’s likely your cluster went down. I’d check the system logs to figure out the reason.
Hi,
Great tutorial – but no longer working
1. Failed during `apt-get update` – ended up using snippets from https://computingforgeeks.com/install-kubernetes-cluster-ubuntu-jammy/?expand_article=1 instead
2. When completed, I continue to see external IP as pending when using “kubectl get svc –namespace default -w wordpress”.
Hi David,
Thanks for your comment. Looks like Kubernetes gpg keys got updated. I’ve tested the whole guide so all should be working now.
Regarding external IPs, by default, Kubernetes services put up a load balancer on the cloud, so the service can only be accessed via the service port from localhost. If not on the cloud it’s best to use an ingress controller such as ingress-nginx.
I just worked through this today, and I’m also getting stuck with a EXTERNAL-IP. After 84 minutes, it’s still .
Hello,
I just worked through this, and similar to David, I’m stuck with a pending External IP. I didn’t have the same issue he had with apt-get update, though. Everything about your guide worked flawlessly with no errors. I’m just stuck here at the end waiting 84 minutes so far with a pending External IP.
I’m able to see the contents of the wordpress application by curling the Internal IP, so I know the application started successfully.
What could cause the External IP to be stuck pending?
Finally, one article on Kubernetes that actually works. Thank you so much.
whenever install single node k8 by following above article its working fine.
but after some time its giving error.
kubectl get node
E0216 12:26:44.266517 369583 memcache.go:265] couldn’t get current server API group list: Get “https://10.81.234.2:6443/api?timeout=32s”: dial tcp 10.81.234.2:6443: i/o timeout
kubectl version
Client Version: v1.28.2
Kustomize Version: v5.0.4-0.20230601165947-6ce0bf390ce3
Unable to connect to the server: dial tcp 10.81.234.2:6443: i/o timeout
Great!.. it worked