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This guide will walk you through the installation of CRI-O Container Runtime on Ubuntu 20.04/18.04. CRI-O is an OCI-based implementation of Kubernetes Container Runtime Interface (CRI) designed to provide an integration path between OCI conformant runtimes and the kubelet.

CRI-O is created to provide following core functionalities:

  • Support multiple image formats including the existing Docker image format
  • Support for multiple means to download images including trust & image verification
  • Container image management (managing image layers, overlay filesystems, etc)
  • Container process lifecycle management
  • Monitoring and logging required to satisfy the CRI
  • Resource isolation as required by the CRI

The libraries used by CRI-O are:

Install CRI-O Container Runtime on Ubuntu 20.04|18.04

We will use pre-built binary packages to install CRI-O container runtime. Follow the steps below to install CRI-O Container Runtime on Ubuntu 20.04|18.04.

Step 1: Update System

Ensure your Ubuntu system is updated. If you’re afraid this could break your system you can skip.

sudo apt update && sudo apt upgrade

It is recommended to reboot your system to ensure it is running on updated version.

sudo systemctl reboot

Step 2: Add CRI-O Kubic repository

Add the Kubic repository which host binary packages for Debian based systems. If using CRI-O with Kubernetes, install the version matching Kubernetes version you’ll setup.

If your Kubernetes version is 1.17, install CRI-O version 1.17.

CRIO_VERSION=1.17
. /etc/os-release
sudo sh -c "echo 'deb http://download.opensuse.org/repositories/devel:/kubic:/libcontainers:/stable/x${NAME}_${VERSION_ID}/ /' >/etc/apt/sources.list.d/devel:kubic:libcontainers:stable.list"

Once the repository is added to your system, import GPG key:

wget -nv https://download.opensuse.org/repositories/devel:kubic:libcontainers:stable/x${NAME}_${VERSION_ID}/Release.key -O- | sudo apt-key add -

Step 3: Install CRI-O on Ubuntu 20.04 | Ubuntu 18.04

When repository is added, update apt cache and install CRI-O on Ubuntu.

sudo apt update
sudo apt install cri-o-${CRIO_VERSION}

Accept installation prompt with y key.

The following additional packages will be installed:
  conmon containers-common containers-golang containers-image libgpgme11 runc
Suggested packages:
  containernetworking-plugins
The following NEW packages will be installed:
  conmon containers-common containers-golang containers-image cri-o-1.17 libgpgme11 runc
0 upgraded, 7 newly installed, 0 to remove and 0 not upgraded.
Need to get 23.3 MB of archives.
After this operation, 107 MB of additional disk space will be used.
Do you want to continue? [Y/n] y

Start and enable crio service:

sudo systemctl enable crio.service
sudo systemctl start crio.service

Service status can be checked with the command:

$ systemctl status crio
● crio.service - Container Runtime Interface for OCI (CRI-O)
     Loaded: loaded (/lib/systemd/system/crio.service; enabled; vendor preset: enabled)
     Active: active (running) since Sun 2020-06-07 20:16:50 CEST; 37s ago
       Docs: https://github.com/cri-o/cri-o
   Main PID: 2461 (crio)
      Tasks: 13
     Memory: 7.7M
     CGroup: /system.slice/crio.service
             └─2461 /usr/bin/crio

Jun 07 20:16:50 ubuntu systemd[1]: Starting Container Runtime Interface for OCI (CRI-O)...
Jun 07 20:16:50 ubuntu systemd[1]: Started Container Runtime Interface for OCI (CRI-O).

Step 4: Using CRI-O on Ubuntu 20.04 | 18.04

The command line tool crioctl can be installed through cri-tools package.

sudo apt install cri-tools

Check existence of crictl command:

$ crictl info
{
  "status": {
    "conditions": [
      {
        "type": "RuntimeReady",
        "status": true,
        "reason": "",
        "message": ""
      },
      {
        "type": "NetworkReady",
        "status": false,
        "reason": "NetworkPluginNotReady",
        "message": "Network plugin returns error: Missing CNI default network"
      }
    ]
  }
}

Pull a test image:

# crictl pull nginx
Image is up to date for docker.io/library/[email protected]:c870bf53de0357813af37b9500cb1c2ff9fb4c00120d5fe1d75c21591293c34d

# crictl pull hello-world
Image is up to date for docker.io/library/[email protected]:6a65f928fb91fcfbc963f7aa6d57c8eeb426ad9a20c7ee045538ef34847f44f1

# crictl pull busybox
Image is up to date for docker.io/library/[email protected]:95cf004f559831017cdf4628aaf1bb30133677be8702a8c5f2994629f637a209

List available images:

# crictl images
IMAGE                           TAG                 IMAGE ID            SIZE
docker.io/library/alpine        latest              a24bb4013296f       5.85MB
docker.io/library/busybox       latest              1c35c44120825       1.44MB
docker.io/library/hello-world   latest              bf756fb1ae65a       20kB
docker.io/library/nginx         latest              4392e5dad77db       136MB

Create pod sandbox config file:

cat >nginx.json<<EOF
{
  "metadata": {
    "name": "nginx-container",
    "attempt": 1
  },
  "image": {
    "image": "nginx"
  },
  "log_path": "nginx.log",
  "linux": {
    "security_context": {
      "namespace_options": {}
    }
  }
}
EOF

cat >net-pod.json<<EOF
{
  "metadata": {
    "name": "networking",
    "uid": "networking-pod-uid",
    "namespace": "default",
    "attempt": 1
  },
  "hostname": "networking",
  "port_mappings": [
    {
      "container_port": 80
    }
  ],
  "log_directory": "/tmp/net-pod",
  "linux": {}
}
EOF

Run the pod

sudo crictl runp net-pod.json
sudo crictl create nginx.json net-pod.json
sudo crictl ps -a

Enjoy using CRI-O on Ubuntu with Kubernetes. If you want to master Kubernetes administration, checkout the courses below.

For installation of CRI-O on CentOS Linux, refer to:

Install CRI-O Container Runtime on CentOS Linux

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