Why Switch from Docker to containerd? A Hands‑On Guide to Installing and Using containerd

Kubernetes Docker Deprecation

Starting with Kubernetes v1.20, Docker support in the kubelet is deprecated and will be removed in future releases. Since Docker’s container management is implemented by containerd, migrating to containerd is the recommended path.

Containerd Overview

Containerd originated inside Docker Engine and has been extracted as an independent open‑source project that provides a stable, portable container runtime. It manages the full container lifecycle: image transfer and storage, container execution, networking, and storage.

Repository: https://github.com/containerd/containerd/

Architecture

Containerd runs as a daemon exposing a gRPC API over a local UNIX socket. The architecture consists of the following core components:

Storage – handles image metadata, storage, and retrieval.

Task – manages container logical structures and interacts with low‑level runtimes.

Event – publishes container events for subscribers.

Runtimes – low‑level runtimes such as runc.

Capabilities

Manage the complete container lifecycle (create → destroy).

Pull and push container images.

Store image and container data.

Invoke runc (or other OCI runtimes) to run containers.

Manage container network interfaces and networking.

From a Kubernetes perspective, using containerd shortens the call chain, reduces component count, improves stability, and consumes fewer node resources.

Installation

Download URL: https://containerd.io/downloads/

# wget https://github.com/containerd/containerd/releases/download/v1.5.2/containerd-1.5.2-linux-amd64.tar.gz
# tar zxf containerd-1.5.2-linux-amd64.tar.gz -C /usr/local/

Generate the default configuration file:

# containerd config default > /etc/containerd/config.toml

Systemd Service Configuration

[Unit]
Description=containerd container runtime
Documentation=https://containerd.io
After=network.target

[Service]
ExecStartPre=/sbin/modprobe overlay
ExecStart=/usr/local/bin/containerd
Delegate=yes
KillMode=process
LimitNOFILE=1048576
LimitNPROC=infinity
LimitCORE=infinity

[Install]
WantedBy=multi-user.target

Reload systemd and start the service:

# systemctl daemon-reload
# systemctl start containerd.service
# systemctl status containerd.service

Using containerd

The lightweight Kubernetes distribution K3s bundles containerd, Flannel, and CoreDNS by default. ctr – native CLI for containerd. crictl – Kubernetes‑specific CLI for container runtimes.

Check the version:

# ctr version
Client:
  Version:  v1.5.2
  Revision: 36cc874494a56a253cd181a1a685b44b58a2e34a
Server:
  Version:  v1.5.2
  Revision: 36cc874494a56a253cd181a1a685b44b58a2e34a

List containers and delete one:

# ctr container list
CONTAINER  IMAGE                         RUNTIME
nginx       docker.io/library/nginx:alpine io.containerd.runc.v2
# ctr container del nginx
# ctr container list

Pull an image and list images:

# ctr images pull docker.io/library/nginx:alpine
# ctr images list

Run a container:

# ctr run -d docker.io/library/nginx:alpine nginx
# ctr container list

All commands are analogous to Docker, so the learning curve remains minimal after Docker support is removed from Kubernetes.

For detailed usage, refer to the official containerd documentation.