Calico, from network software provider Tigera, is a third-party plugin for Kubernetes geared to make full network connectivity more flexible and easier. Out of the box, Kubernetes provides the NetworkPolicy API for managing network policies within the cluster. The problem many Kubernetes admins find (especially those new to the technology) is that network can quickly become a rather complicated mess of YAML configurations, where you must configure traffic ingress and egress properly, or communication between Kubernetes objects (such as pods and containers) can be difficult.
That’s where the likes of Calico come into play. Because not every Kubernetes network plugin supports NetworkPolicy API, it’s important that you select a plugin that will take care of your needs. For example, the most popular Kubernetes network plugin is Flannel, which cannot configure network policies. With Calico, you can significantly enhance the Kubernetes networking configuration.
Take, for instance, the feature limitations found in the default NetworkPolicy, which are:
- Policies are limited to a single environment and are applied only to pods marked with labels.
- You can only apply rules to pods, environments, or subnets.
- Rules can only contain protocols, numerical ports, or named ports.
When you add the Calico plugin, the features are extended as such:
- Policies can be applied to pods, containers, virtual machines, or interfaces.
- Rules can contain a specific action (such as restriction, permission, or logging).
- Rules can contain ports, port ranges, protocols, HTTP/ICMP attributes, IPs, subnets, or selectors for nodes (such as hosts or environments).
- Traffic flow can be controlled via DNAT settings and policies.
Calico also supports multiple data planes, which allows you to choose the technology that best suits the needs of your project (including the pure Linux eBPF data plane). Other features include:
- Highly performant.
- Massive scalability.
- Interoperability with current non-K8s workloads.
- Full Kubernetes network policy support.
- Very active development community.
To make Calico even more appealing, it’s available for use on all popular cloud platforms, such as Amazon Web Services, Microsoft Azure, the Google Cloud Platform, IBM, Red Hat OpenShift and SUSE’s Rancher.
Or, if you prefer, you can deploy Calico on bare metal in your data center.
Let’s walk through the process of installing Calico on a small Kubernetes cluster. We’ll demonstrate on a cluster running on instances of Ubuntu Server 20.04, but the process should be the same, regardless of your platform. So long as you have access to kubectl, you should be good to go.
The first method will assume you already have your Kubernetes cluster up and running, while the second method starts on a bare-metal Ubuntu Server instance.
First I will show you how to install Calico for a small number of nodes (50 or less). First, download the manifest with the command:
curl https://docs.projectcalico.org/manifests/calico-typha.yaml -o calico.yaml
Once the file download completes, apply it with the command:
kubectl apply -f calico.yaml
When the command completes, you should see that a number of new objects/services have been created, such as:
If you need to deploy Calico to a cluster with more than 50 nodes, you need to first edit the YAML file. Open the file with the command:
In that file, look for the line:
To configure that line, you need to set one replica for every 200 nodes. So if you have 600 nodes, you’d set it to:
One thing to keep in mind is that you should set no more than 20 replicas and (in production) you should use a minimum of three replicas.
The next step is to install the calicoctl command. Download the executable with the command:
curl -o calicoctl -O -L "https://github.com/projectcalico/calicoctl/releases/download/v3.19.1/calicoctl"
After the executable downloads to your system, move it into a directory in your path, such as /usr/local/bin/, with the command:
sudo mv calicoctl /usr/local/bin/
Next, give the file executable permissions with the command:
sudo chmod +x /usr/local/bin/calicoctl
Verify the installation by running the command:
You should see a listing of how the command is used.
Installing on bare metal
Let’s take a look at how to install Calico on a bare metal instance of Ubuntu Server 20.04. Here are the steps:
Step 1: Update apt and install the necessary dependencies with the commands:
sudo apt-get update
sudo apt-get install -y apt-transport-https ca-certificates curl
Step 2: Download the Google Cloud GPG key with the command:
sudo curl -fsSLo /usr/share/keyrings/kubernetes-archive-keyring.gpg https://packages.cloud.google.com/apt/doc/apt-key.gpg
Step 3: Add the Kubernetes repository with the command:
echo "deb [signed-by=/usr/share/keyrings/kubernetes-archive-keyring.gpg] https://apt.kubernetes.io/ kubernetes-xenial main" | sudo tee /etc/apt/sources.list.d/kubernetes.list
Step 4: Update apt and install kubeadm/kubectl with the commands:
sudo apt-get update
sudo apt-get install -y kubelet kubeadm kubectl
sudo apt-mark hold kubelet kubeadm kubectl
Step 5: Install Docker with the command:
sudo apt-get install docker.io -y
Step 6: Add your user to the docker group with the command:
sudo usermod -aG docker $USER
Log out and log back in.
Step 6: Disable swap by opening the fstab file with the command:
sudo nano /etc/fstab
Look for the line that starts with:
Change that line to start with:
Save and close the file.
Issue the command:
sudo swapoff -a
Step 7: Initialize Kubernetes with the command:
sudo kubeadm init --pod-network-cidr=SERVER/16
Where SERVER is the IP address of the hosting server.
Step 8: Create the necessary directory and copy the configuration files with the commands:
mkdir -p $HOME/.kube
sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
sudo chown $(id -u):$(id -g) $HOME/.kube/config
Step 9: Install the Tigera Calico operator with the command:
kubectl create -f https://docs.projectcalico.org/manifests/tigera-operator.yaml
Download the necessary custom Calico resources YAML with the command:
Open that file and check for any necessary customizations you might want with the command:
After you’ve customized the YAML, save and close the file and apply it with the command:
kubectl create -f custom-resources.yaml
Wait a few minutes and confirm all of Calico pods are running with the command:
watch kubectl get pods -n calico-system
When all of the pods have a status of Running, you’ll need to remove the taints on the master with the command:
kubectl taint nodes --all node-role.kubernetes.io/master-
If you issue the command:
kubectl get nodes -o wide
You should see that your Kubernetes cluster is now up and running with Calico. At this point, you should check out the official Calico Networking documentation to learn how to make the most out of your new deployment.
Amazon Web Services, IBM, Red Hat and Tigera are sponsors of The New Stack.