Onur Yasarlar
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Linux
Kubernetes
Installing Container Runtime Interface
Getting Started
You can select one of the supported container runtime interfaces for your Kubernetes cluster infrastructure. Since Kubernetes is deprecating Docker as a container runtime after v1.20, I choose
containerd as my runtime interface and writing an Ansible role to install it. Let's do deep dive on how to install containerd. You can find my Ansible role here.Installing Prerequisites
containerd expects some kernel parameters and kernel modules to be set persistently. I am handling that step in a separate playbook as below:
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---
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- name: Enable kernel module
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lineinfile:
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path: /etc/modules-load.d/containerd.conf
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line: "{{ item }}"
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state: present
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create: true
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mode: '0644'
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loop:
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- overlay
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- br_netfilter
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- name: Reload kernel modules
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modprobe:
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name: "{{ item }}"
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state: present
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loop:
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- overlay
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- br_netfilter
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- name: Setup required sysctl params
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sysctl:
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name: "{{ item.name }}"
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value: "{{ item.value }}"
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sysctl_file: /etc/sysctl.d/99-kubernetes-cri.conf
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reload: true
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loop:
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- { name: net.bridge.bridge-nf-call-iptables, value: 1 }
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- { name: net.ipv4.ip_forward, value: 1}
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- { name: net.bridge.bridge-nf-call-ip6tables, value: 1}
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Installing containerd runtime interface
I am covering containerd installation on Centos 7, Ubuntu 18.04, and Ubuntu 20.04. Each operating system has its own installation requirements. I prefer to split them into different plays and include them in my
tasks/main.yml as below:1
- name: Install containerd
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include_tasks: "install_{{ ansible_distribution | lower }}.yaml"
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So each supported operating system calls its own
yaml file as below:CENTOS 7
Ubuntu 18.04 / 20.04
tasks/install_centos.yaml
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---
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- name: Install on CentOS 7
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block:
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- name: Install required packages
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package:
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name:
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- yum-utils
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- device-mapper-persistent-data
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- lvm2
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state: present
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- name: Create docker-ce package repository
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get_url:
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url: "https://download.docker.com/linux/centos/docker-ce.repo"
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dest: /etc/yum.repos.d/docker-ce.repo
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owner: root
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group: root
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mode: '0644'
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- name: Install containerd.io
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package:
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name: containerd.io
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state: present
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when: ansible_distribution_major_version | int == 7
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tasks/install_ubuntu.yaml
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---
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- name: Install containerd on Ubuntu 18.04 / 20.04
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apt:
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name: containerd
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update_cache: yes
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when: (ansible_distribution_version.split(".") | join == "1804") or
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(ansible_distribution_version.split(".") | join == "2004")
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containerd version is not defined in the current version of the Ansible role. In the near future, I can add it to provide more stability but for now, I will go with the latest version always.
Configuration
Once the binary is installed, we need to create the configuration file under
/etc/containerd/config.toml. Then we will need to enable and restart the service so the new configuration can be read by the daemon. Since the configuration step is common on all operating systems, I created a single play and include it in the main play. Let's take a look at the configuration code:tasks/configure.yaml
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---
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- name: Create /etc/containerd
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file:
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path: /etc/containerd
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state: directory
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mode: '0755'
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- name: Check if /etc/containerd/config.toml exists
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stat:
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path: /etc/containerd/config.toml
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register: containerd_config
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- name: Copy containerd configuration
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shell: "containerd config default > /etc/containerd/config.toml"
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args:
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warn: no
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tags: ['skip_ansible_lint']
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when: not containerd_config.stat.exists
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notify: restart containerd
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- name: Enable containerd
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service:
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name: containerd
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enabled: true
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Putting things together
All the above steps are included in the main playbook of the role as below:
tasks/main.yml
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- name: Handle prereqs
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include_tasks: prereq.yaml
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- name: Install containerd
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include_tasks: "install_{{ ansible_distribution | lower }}.yaml"
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- name: Configure containerd
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include_tasks: configure.yaml
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Calling this role will enable us to install containerd on supported operating systems. Now we can continue with installing kubeadm, kubelet, and kubectl.