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Container runtimes concept 10

{{< feature-state for_k8s_version="v1.6" state="stable" >}} To run containers in Pods, Kubernetes uses a container runtime. Here are the installation instructions for various runtimes.

{{< caution >}} A flaw was found in the way runc handled system file descriptors when running containers. A malicious container could use this flaw to overwrite contents of the runc binary and consequently run arbitrary commands on the container host system.

Please refer to CVE-2019-5736 for more information about the issue. {{< /caution >}}

Applicability

{{< note >}} This document is written for users installing CRI onto Linux. For other operating systems, look for documentation specific to your platform. {{< /note >}}

Cgroup drivers

When systemd is chosen as the init system for a Linux distribution, the init process generates and consumes a root control group (cgroup) and acts as a cgroup manager. Systemd has a tight integration with cgroups and will allocate cgroups per process. It's possible to configure your container runtime and the kubelet to use cgroupfs. Using cgroupfs alongside systemd means that there will be two different cgroup managers.

Control groups are used to constrain resources that are allocated to processes. A single cgroup manager will simplify the view of what resources are being allocated and will by default have a more consistent view of the available and in-use resources. When we have two managers we end up with two views of those resources. We have seen cases in the field where nodes that are configured to use cgroupfs for the kubelet and Docker, and systemd for the rest of the processes running on the node becomes unstable under resource pressure.

Changing the settings such that your container runtime and kubelet use systemd as the cgroup driver stabilized the system. Please note the native.cgroupdriver=systemd option in the Docker setup below.

{{< caution >}} Changing the cgroup driver of a Node that has joined a cluster is highly unrecommended. If the kubelet has created Pods using the semantics of one cgroup driver, changing the container runtime to another cgroup driver can cause errors when trying to re-create the PodSandbox for such existing Pods. Restarting the kubelet may not solve such errors. The recommendation is to drain the Node from its workloads, remove it from the cluster and re-join it. {{< /caution >}}

Docker

On each of your machines, install Docker. Version 19.03.11 is recommended, but 1.13.1, 17.03, 17.06, 17.09, 18.06 and 18.09 are known to work as well. Keep track of the latest verified Docker version in the Kubernetes release notes.

Use the following commands to install Docker on your system:

{{< tabs name="tab-cri-docker-installation" >}} {{% tab name="Ubuntu 16.04+" %}}

# (Install Docker CE)
## Set up the repository:
### Install packages to allow apt to use a repository over HTTPS
sudo apt-get update && sudo apt-get install -y \
  apt-transport-https ca-certificates curl software-properties-common gnupg2

# Add Docker's official GPG key:
curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -

# Add the Docker apt repository:
sudo add-apt-repository \
  "deb [arch=amd64] https://download.docker.com/linux/ubuntu \
  $(lsb_release -cs) \
  stable"

# Install Docker CE
sudo apt-get update && sudo apt-get install -y \
  containerd.io=1.2.13-2 \
  docker-ce=5:19.03.11~3-0~ubuntu-$(lsb_release -cs) \
  docker-ce-cli=5:19.03.11~3-0~ubuntu-$(lsb_release -cs)

# Set up the Docker daemon
cat <<EOF | sudo tee /etc/docker/daemon.json
{
  "exec-opts": ["native.cgroupdriver=systemd"],
  "log-driver": "json-file",
  "log-opts": {
    "max-size": "100m"
  },
  "storage-driver": "overlay2"
}
EOF

sudo mkdir -p /etc/systemd/system/docker.service.d

# Restart Docker
sudo systemctl daemon-reload
sudo systemctl restart docker

{{% /tab %}} {{% tab name="CentOS/RHEL 7.4+" %}}

# (Install Docker CE)
## Set up the repository
### Install required packages
sudo yum install -y yum-utils device-mapper-persistent-data lvm2

## Add the Docker repository
sudo yum-config-manager --add-repo \
  https://download.docker.com/linux/centos/docker-ce.repo

# Install Docker CE
sudo yum update -y && sudo yum install -y \
  containerd.io-1.2.13 \
  docker-ce-19.03.11 \
  docker-ce-cli-19.03.11

## Create /etc/docker
sudo mkdir /etc/docker

# Set up the Docker daemon
cat <<EOF | sudo tee /etc/docker/daemon.json
{
  "exec-opts": ["native.cgroupdriver=systemd"],
  "log-driver": "json-file",
  "log-opts": {
    "max-size": "100m"
  },
  "storage-driver": "overlay2",
  "storage-opts": [
    "overlay2.override_kernel_check=true"
  ]
}
EOF

sudo mkdir -p /etc/systemd/system/docker.service.d

# Restart Docker
sudo systemctl daemon-reload
sudo systemctl restart docker

{{% /tab %}} {{< /tabs >}}

If you want the docker service to start on boot, run the following command:

sudo systemctl enable docker

Refer to the official Docker installation guides for more information.

CRI-O

This section contains the necessary steps to install CRI-O as CRI runtime.

Use the following commands to install CRI-O on your system:

{{< note >}} The CRI-O major and minor versions must match the Kubernetes major and minor versions. For more information, see the CRI-O compatibility matrix. {{< /note >}}

Prerequisites

sudo modprobe overlay
sudo modprobe br_netfilter

# Set up required sysctl params, these persist across reboots.
cat <<EOF | sudo tee /etc/sysctl.d/99-kubernetes-cri.conf
net.bridge.bridge-nf-call-iptables  = 1
net.ipv4.ip_forward                 = 1
net.bridge.bridge-nf-call-ip6tables = 1
EOF

sudo sysctl --system

{{< tabs name="tab-cri-cri-o-installation" >}} {{% tab name="Debian" %}}

To install CRI-O on the following operating systems, set the environment variable $OS to the appropriate field in the following table:

Operating system $OS
Debian Unstable Debian_Unstable
Debian Testing Debian_Testing

Then, set `$VERSION` to the CRI-O version that matches your Kubernetes version. For instance, if you want to install CRI-O 1.18, set `VERSION=1.18`. You can pin your installation to a specific release. To install version 1.18.3, set `VERSION=1.18:1.18.3`.

Then run

cat <<EOF | sudo tee /etc/apt/sources.list.d/devel:kubic:libcontainers:stable.list
"deb https://download.opensuse.org/repositories/devel:/kubic:/libcontainers:/stable/$OS/ /"
EOF
cat <<EOF | sudo tee /etc/apt/sources.list.d/devel:kubic:libcontainers:stable:cri-o:$VERSION.list
"deb http://download.opensuse.org/repositories/devel:/kubic:/libcontainers:/stable:/cri-o:/$VERSION/$OS/ /"
EOF

curl -L https://download.opensuse.org/repositories/devel:kubic:libcontainers:stable:cri-o:$VERSION/$OS/Release.key | sudo apt-key add -
curl -L https://download.opensuse.org/repositories/devel:/kubic:/libcontainers:/stable/$OS/Release.key | sudo apt-key add -

sudo apt-get update
sudo apt-get install cri-o cri-o-runc

{{% /tab %}}

{{% tab name="Ubuntu" %}}

To install on the following operating systems, set the environment variable $OS to the appropriate field in the following table:

Operating system $OS
Ubuntu 20.04 xUbuntu_20.04
Ubuntu 19.10 xUbuntu_19.10
Ubuntu 19.04 xUbuntu_19.04
Ubuntu 18.04 xUbuntu_18.04

Then, set `$VERSION` to the CRI-O version that matches your Kubernetes version. For instance, if you want to install CRI-O 1.18, set `VERSION=1.18`. You can pin your installation to a specific release. To install version 1.18.3, set `VERSION=1.18:1.18.3`.

Then run

sudo echo "deb https://download.opensuse.org/repositories/devel:/kubic:/libcontainers:/stable/$OS/ /" > /etc/apt/sources.list.d/devel:kubic:libcontainers:stable.list
sudo echo "deb http://download.opensuse.org/repositories/devel:/kubic:/libcontainers:/stable:/cri-o:/$VERSION/$OS/ /" > /etc/apt/sources.list.d/devel:kubic:libcontainers:stable:cri-o:$VERSION.list

curl -L https://download.opensuse.org/repositories/devel:kubic:libcontainers:stable:cri-o:$VERSION/$OS/Release.key | sudo apt-key add -
curl -L https://download.opensuse.org/repositories/devel:/kubic:/libcontainers:/stable/$OS/Release.key | sudo apt-key add -

sudo apt-get update
sudo apt-get install cri-o cri-o-runc

{{% /tab %}}

{{% tab name="CentOS" %}}

To install on the following operating systems, set the environment variable $OS to the appropriate field in the following table:

Operating system $OS
Centos 8 CentOS_8
Centos 8 Stream CentOS_8_Stream
Centos 7 CentOS_7

Then, set `$VERSION` to the CRI-O version that matches your Kubernetes version. For instance, if you want to install CRI-O 1.18, set `VERSION=1.18`. You can pin your installation to a specific release. To install version 1.18.3, set `VERSION=1.18:1.18.3`.

Then run

sudo curl -L -o /etc/yum.repos.d/devel:kubic:libcontainers:stable.repo https://download.opensuse.org/repositories/devel:/kubic:/libcontainers:/stable/$OS/devel:kubic:libcontainers:stable.repo
sudo curl -L -o /etc/yum.repos.d/devel:kubic:libcontainers:stable:cri-o:$VERSION.repo https://download.opensuse.org/repositories/devel:kubic:libcontainers:stable:cri-o:$VERSION/$OS/devel:kubic:libcontainers:stable:cri-o:$VERSION.repo
sudo yum install cri-o

{{% /tab %}}

{{% tab name="openSUSE Tumbleweed" %}}

sudo zypper install cri-o

{{% /tab %}} {{% tab name="Fedora" %}}

Set $VERSION to the CRI-O version that matches your Kubernetes version. For instance, if you want to install CRI-O 1.18, VERSION=1.18
You can find available versions with:

sudo dnf module list cri-o

CRI-O does not support pinning to specific releases on Fedora.

Then run

sudo dnf module enable cri-o:$VERSION
sudo dnf install cri-o

{{% /tab %}} {{< /tabs >}}

Start CRI-O

sudo systemctl daemon-reload
sudo systemctl start crio

Refer to the CRI-O installation guide for more information.

Containerd

This section contains the necessary steps to use containerd as CRI runtime.

Use the following commands to install Containerd on your system:

Prerequisites

cat <<EOF | sudo tee /etc/modules-load.d/containerd.conf
overlay
br_netfilter
EOF

sudo modprobe overlay
sudo modprobe br_netfilter

# Setup required sysctl params, these persist across reboots.
cat <<EOF | sudo tee /etc/sysctl.d/99-kubernetes-cri.conf
net.bridge.bridge-nf-call-iptables  = 1
net.ipv4.ip_forward                 = 1
net.bridge.bridge-nf-call-ip6tables = 1
EOF

sudo sysctl --system

Install containerd

{{< tabs name="tab-cri-containerd-installation" >}} {{% tab name="Ubuntu 16.04" %}}

# (Install containerd)
## Set up the repository
### Install packages to allow apt to use a repository over HTTPS
sudo apt-get update && sudo apt-get install -y apt-transport-https ca-certificates curl software-properties-common

## Add Docker's official GPG key
curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -

## Add Docker apt repository.
sudo add-apt-repository \
    "deb [arch=amd64] https://download.docker.com/linux/ubuntu \
    $(lsb_release -cs) \
    stable"

## Install containerd
sudo apt-get update && sudo apt-get install -y containerd.io

# Configure containerd
sudo mkdir -p /etc/containerd
sudo containerd config default > /etc/containerd/config.toml

# Restart containerd
sudo systemctl restart containerd

{{% /tab %}} {{% tab name="CentOS/RHEL 7.4+" %}}

# (Install containerd)
## Set up the repository
### Install required packages
sudo yum install -y yum-utils device-mapper-persistent-data lvm2

## Add docker repository
sudo yum-config-manager \
    --add-repo \
    https://download.docker.com/linux/centos/docker-ce.repo

## Install containerd
sudo yum update -y && sudo yum install -y containerd.io

## Configure containerd
sudo mkdir -p /etc/containerd
sudo containerd config default > /etc/containerd/config.toml

# Restart containerd
sudo systemctl restart containerd

{{% /tab %}} {{% tab name="Windows (PowerShell)" %}}

# (Install containerd)
# download containerd
cmd /c curl -OL https://github.com/containerd/containerd/releases/download/v1.4.0-beta.2/containerd-1.4.0-beta.2-windows-amd64.tar.gz
cmd /c tar xvf .\containerd-1.4.0-beta.2-windows-amd64.tar.gz

# extract and configure
Copy-Item -Path ".\bin\" -Destination "$Env:ProgramFiles\containerd" -Recurse -Force
cd $Env:ProgramFiles\containerd\
.\containerd.exe config default | Out-File config.toml -Encoding ascii

# review the configuration. depending on setup you may want to adjust:
# - the sandbox_image (kubernetes pause image)
# - cni bin_dir and conf_dir locations
Get-Content config.toml

# start containerd
.\containerd.exe --register-service
Start-Service containerd

{{% /tab %}} {{< /tabs >}}

systemd

To use the systemd cgroup driver in /etc/containerd/config.toml with runc set

[plugins."io.containerd.grpc.v1.cri".containerd.runtimes.runc]
  ...
  [plugins."io.containerd.grpc.v1.cri".containerd.runtimes.runc.options]
    SystemdCgroup = true

When using kubeadm, manually configure the cgroup driver for kubelet

Other CRI runtimes: frakti

Refer to the Frakti QuickStart guide for more information.