Containerd APT vs Binary (Part 1)

# Kubernetes Container Runtime Installation Guide (Binary vs APT Method)

Introduction¶

When setting up Kubernetes, the choice of installation method for the container runtime (containerd) impacts how additional components like runc and CNI plugins are managed. This guide clarifies the differences between installing containerd via binary method versus APT package manager, particularly in how CNI plugins are handled.

1️⃣ Installing Container Runtime using APT (Recommended for kubeadm)¶

When you install containerd via apt, the following behavior occurs:

• runc: Automatically installed as a dependency.
• CNI Plugins: Not included by default in /opt/cni/bin/.
• containerd: Installed and configured via systemd.

Steps for APT Method:¶

1. Install dependencies:

   sudo apt update
   sudo apt install -y containerd
   

2. Verify installation:

   containerd --version
   

3. Since CNI plugins are not installed, Kubernetes will require a CNI plugin (like Flannel, Calico, etc.) to be deployed separately. After kubeadm init, you must install a CNI plugin:

   kubectl apply -f <CNI-YAML>
   

   Example for Calico:

   kubectl apply -f https://docs.projectcalico.org/manifests/calico.yaml
   

Key Considerations for APT Method:¶

• ✅ Easier & recommended for kubeadm setups
• ❌ CNI plugins must be installed separately after kubeadm init
• ✅ Automatic runc installation

2️⃣ Installing Container Runtime using Binary (More Manual Steps)¶

When installing via binaries, everything is managed manually, including containerd, runc, and CNI plugins.

Steps for Binary Method:¶

1. Download and install containerd, runc, and CNI plugins manually:

   wget https://github.com/containerd/containerd/releases/download/v1.x.x/containerd-1.x.x-linux-amd64.tar.gz
   sudo tar Cxzvf /usr/local containerd-1.x.x-linux-amd64.tar.gz
   

2. Install runc manually:

   wget https://github.com/opencontainers/runc/releases/download/v1.x.x/runc.amd64
   sudo install -m 755 runc.amd64 /usr/local/sbin/runc
   

3. Install CNI plugins manually:

   wget https://github.com/containernetworking/plugins/releases/download/v1.x.x/cni-plugins-linux-amd64-v1.x.x.tgz
   sudo mkdir -p /opt/cni/bin
   sudo tar Cxzvf /opt/cni/bin cni-plugins-linux-amd64-v1.x.x.tgz
   

Key Considerations for Binary Method:¶

• ✅ More control over versions & configurations
• ❌ Manual installation of runc & CNI plugins is required
• ❌ More complex setup, requiring extra verification

Conclusion: Choosing the Right Method¶

If using kubeadm, the APT method is strongly recommended. The binary method is useful for advanced users needing strict control over versions but requires extra manual steps.

Final Reminder: What Changes Between These Methods?¶

• apt install containerd automatically installs runc, but does not install CNI plugins.
• The binary method requires manual installation of both runc and CNI plugins.
• In both methods, a CNI plugin must be applied in Kubernetes for networking to function.
• For Kubernetes cluster setup using kubeadm, just installing a CNI plugin via YAML is enough (you don’t need to manually place CNI binaries in /opt/cni/bin/).

This guide ensures you know exactly what each method does and what additional steps are required. 🚀