Install and Configure containerd on a Linux Host

In this challenge, you will practice installing and configuring containerd: obtaining the release binaries, placing them in the correct locations, adding the container runtime and CNI plugins to the system, and starting a container with full networking support.

#containerd #ctr #runc #oci-runtime #cni

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In this challenge, you will need to install and configure containerd on a Linux host. Follow the steps below to complete the challenge.

Main components of a containerd installation: ctr, containerd, containerd-shim, runc, and CNI plugins.

First things first, obtain relatively fresh containerd binaries:

Hint 1

One of the main installation options mentioned in the official Getting started with containerd guide is to download containerd binaries from the project's GitHub Releases page.

Hint 2

Installing the containerd.io package (maintained by Docker) is also an option, but you'll likely get a more dated version of the daemon.

With the containerd binaries in place, start containerd as a systemd service:

Hint 3

The maintainers of the containerd project kindly provide a systemd unit file that you can use to launch containerd on your system.

Surprisingly or not, containerd itself cannot run any containers - it needs a lower-level container runtime for that. Install an OCI-compatible container runtime, such as runc or crun:

Hint 4

If you choose to install runc, it should be as simple as downloading a statically linked binary from the GitHub Releases page, placing it in one of the directories in your $PATH, and making it executable.

Neither containerd nor runc can do container networking by themselves - they need CNI plugins to be present on the host. Install the CNI plugins and configure a bridge network with the following parameters:

Bridge name: bridge0
Host-local IPAM
- Subnet: 172.18.0.0/24
- Gateway: 172.18.0.1

Hint 5

To install the CNI plugins, you can download the release binaries from the GitHub Releases page and extract them to /opt/cni/bin.

Hint 6

containerd expects the CNI configuration files to be present in /etc/cni/net.d. There are many ways to configure a bridge CNI network, but the following is a good starting point:

{
  "type": "bridge",
  "bridge": "bridge0",
  "name": "bridge",
  "isGateway": true,
  "ipMasq": true,
  "ipam": {
    "type": "host-local",
    "ranges": [
      [{"subnet": "172.18.0.0/24"}]
    ],
    "routes": [{"dst": "0.0.0.0/0"}]
  },
  "cniVersion": "1.0.0"
}

Finally, start an Nginx container with full networking support using the ctr CLI:

Hint 7

With ctr, you have to explicitly pull the image before you can start a container.

Hint 8

By default, ctr run will not enable networking for the container. You can use the --cni flag to enable the use of CNI plugins.

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