Sometimes you just need a Kubernetes cluster, and you don’t want to mess around. Maybe you want to test out a small application, or create a development environment for yourself. Whatever your goal, you want it quick, and you want it simple. That’s what we’re going to do. This article is a quick and dirty guide to creating a single-node Kubernetes cluster using Kubeadm, a new tool the k8s community created to simplify the deployment process. (It’s straightforward to create multi-node deployments, but we’ll cover that in later articles.)

Create the VM

These instructions were tested using a Virtualbox VM, but in theory they should be the same for a bare metal deployment. (You can find instructions for creating the VM here.) A couple of things to note about the VM:

• Allocate at least 2 vCPUs, even if you’re overcommitting your resources; there are pieces of this example that won’t start with just one.
• Try to allocate at least 4096 MB of RAM and 20 GB of drive space.
• You should have Ubuntu 16.04 installed.
• Set the default network adapter to connect to the “Bridged adapter” to enable traffic between the VM and the host machine.

Prepare the VM

There are a few things you need to do to get the VM ready. Specifically, you need to turn off the swap, tweak some settings, and make sure you have the prerequisites installed.  To do that, follow these steps:

1. Change to root:

   sudo su

2. Turn off swap: To do this, you will first need to turn it off directly …

   swapoff -a

   … then comment out the reference to swap in /etc/fstab.  Start by editing the file:

   vi /etc/fstab

   Then comment out the appropriate line, as in:

   # /etc/fstab: static file system information.
   #
   # Use 'blkid' to print the universally unique identifier for a
   # device; this may be used with UUID= as a more robust way to name devices
   # that works even if disks are added and removed. See fstab(5).
   #
   # <file system> <mount point>   <type>  <options>    <dump>  <pass>
   # / was on /dev/sda1 during installation
   UUID=1d343a19-bd75-47a6-899d-7c8bc93e28ff /            ext4 errors=remount-ro 0    1
   # swap was on /dev/sda5 during installation
   #UUID=d0200036-b211-4e6e-a194-ac2e51dfb27d none         swap sw           0    0

3. Now configure iptables to receive bridged network traffic. First edit the sysctl.conf file:

   vi /etc/ufw/sysctl.conf

   And add the following lines to the end:

   net/bridge/bridge-nf-call-ip6tables = 1
   net/bridge/bridge-nf-call-iptables = 1
   net/bridge/bridge-nf-call-arptables = 1
   

4. Reboot so the changes take effect.
5. Install ebtables and ethtool:

   sudo su
   apt-get install ebtables ethtool

6. Reboot once more.

Install Kubeadm

OK, now we’re ready to go ahead and do the install.  For a full description of this process, you can see the documentation, but here’s the quick and dirty version:

1. Install Docker:

   sudo su
   
   apt-get update
   apt-get install -y docker.io

2. Install HTTPS support (if necessary):

   apt-get update 
   apt-get install -y apt-transport-https

3. Install Curl (if necessary):

   apt-get install curl

4. Retrieve the key for the Kubernetes repo and add it to your key manager:

   curl -s https://packages.cloud.google.com/apt/doc/apt-key.gpg | apt-key add -

5. Add the kubernetes repo to your system.

   cat <<EOF >/etc/apt/sources.list.d/kubernetes.list
   deb http://apt.kubernetes.io/ kubernetes-xenial main
   EOF

6. Actually install the three pieces you’ll need, kubeadm, kubelet, and kubectl:

   apt-get update
   apt-get install -y kubelet kubeadm kubectl

At this point you should have all the tools you need, so you should be ready to go ahead and actually deploy a k8s cluster.

Create a cluster

Now that we have Kubeadm installed, we’ll go ahead and create a new cluster.  Part of this process is choosing a network provider, and there are several choices; we’ll use Calico for this example.

1. Create the actual cluster.  For Calico, we need to add the –pod-network-cidr switch, as in:

   kubeadm init --pod-network-cidr=192.168.0.0/16

   This will crank for a while, eventually giving you output something like this:

   To start using your cluster, you need to run (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
   
   You should now deploy a pod network to the cluster.
   Run "kubectl apply -f [podnetwork].yaml" with one of the options listed at:
     http://kubernetes.io/docs/admin/addons/
   
   You can now join any number of machines by running the following on each node
   as root:
   
     kubeadm join --token 354502.d6a9a425d5fa8f2e 192.168.0.9:6443 --discovery-token-ca-cert-hash sha256:ad7c5e8a0c909ed36a87452e65fa44b1c2a9729cef7285eb551e2f126a1d6a54

   Notice that last bit, about joining other machines to the cluster; we’re not going to do that, but you do have that option.

2. Prepare your system for adding workloads, including the network plugin.  Open a NEW terminal window and execute the commands kubeadm gave you:

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

3. Install the Calico network plugin:

   kubectl apply -f https://docs.projectcalico.org/v2.6/getting-started/kubernetes/installation/hosted/kubeadm/1.6/calico.yaml

4. Check to see if the pods are running:

   kubectl get pods --all-namespaces

   The pods will start up over a short period of time.

5. Untaint the master so that it will be available for scheduling workloads:

   kubectl taint nodes --all node-role.kubernetes.io/master-

At this point you should have a fully-functional kubernetes cluster on which you can run workloads.

Test the cluster

Now let’s make sure everything’s working properly by installing the Sock Shop sample application.  Follow these steps:

1. Create the namespace in which the Sock Shop will live:

   kubectl create namespace sock-shop

2. Create the actual Sock Shop application:

   kubectl apply -n sock-shop -f "https://github.com/microservices-demo/microservices-demo/blob/master/deploy/kubernetes/complete-demo.yaml?raw=true"

   Use kubectl get pods –all-namespaces to make sure the pods are all running.

3. We’ll interact with it via the front-end service, so find the IP address for that service:

   kubectl -n sock-shop get svc front-end
   
   NAME        CLUSTER-IP       EXTERNAL-IP   PORT(S)        AGE
   front-end   10.110.250.153   <nodes>       80:30001/TCP   59s

   Visit http://<cluster-ip> (in this case, http://10.110.250.153) with your browser.  You should see the WeaveSocks interface:

   

   (NOTE:  If you are running VirtalBox on Windows, you may run into a bug that only enables you to view the application on port 30001.)

4. You can also verify that you can reach the interface from the host machine.  You’ll first need to find the proper IP address.  Your VM will have several, which you should be able to find using:

   ifconfig

   You’re looking for an IP address in the same range as your host machine, most likely the Ethernet adapter.  For example, in my case, it was this section:

   enp0s3 Link encap:Ethernet  HWaddr 08:00:27:7c:14:fd  
          inet addr:192.168.2.50  Bcast:192.168.2.255  Mask:255.255.255.0
          inet6 addr: fe80::7638:2441:3326:b242/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:415485 errors:0 dropped:0 overruns:0 frame:0
          TX packets:166889 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:621031284 (621.0 MB)  TX bytes:12020009 (12.0 MB)

5. Now take that IP address and point the browser on your host machine to that IP on port 30001:

   http://:30001

   (In my case that would be http://192.168.2.50:30001.)

   If all has gone well, you will see the Sock Shop, just as you did on the VM:

   

Cleaning up

We haven’t done much, but if you want to start over, you can do the following:

To remove the Sock Shop:

kubectl delete namespace sock-shop

To remove the entire cluster:

sudo kubeadm reset

That’s it!

Moving on

So at this point you know how to:

1. Prepare a VM for Kubeadm
2. Install Kubeadm
3. Deploy a Kubernetes cluster
4. Deploy a sample application on a Kubernetes application
5. Remove the sample application
6. Remove the cluster

 
In future articles, we’ll talk about tasks such as creating custom applications and adding additional nodes to clusters.  You can also check out our previous tutorial on creating a Kubernetes deployment, or spend an hour learning the basics of Kubernetes with our free Kubernetes mini-boot camp.