2. Kubernetes cluster¶

2.1. Introduction¶

This document aims to explain how to construct the Exastro IT Automation's deploy destination, the Kubernetes cluster, using Kubespray.

2.2. Pre-requisites¶

The user must have an Ansible execution environment that can use Kubespray.
The user must have somewhere to install the Kubernetes cluster (This guide uses the following OS: Red Hat Enterprise Linux 8).

2.3. Kubernetes cluster structure¶

This guide follows steps noted on the official website. The steps might change depending on the Kubernetes version.

Official site: https://kubernetes.io/ja/docs/setup/production-environment/tools/kubespray/

2.3.1. Preparing the Ansible environment¶

Install tools¶

Install the following tools to the Kubespray execution environment.

Change to root user
リスト 2.1 Command¶
```
sudo su -
```
Install Python3.9
リスト 2.2 Command¶
```
yum -y install python39
```
Install pip3.9
リスト 2.3 Command¶
```
pip3.9 install ruamel-yaml
```
Install git
リスト 2.4 Command¶
```
yum -y install git
```

注釈

The steps can be skipped if the different softwares are already installed.

Configure HOST¶

Next, we will register the destination inforamtion to the HOSTS.

※In this guide, we will use 3 Kubernetes clusters.

リスト 2.5 Command¶

vi /etc/hosts

リスト 2.6 hosts¶

# Add Kubernetes cluster information
168.1.1 ha-conf-k8s-01.cluster.local ha-conf-k8s-01
168.1.2 ha-conf-k8s-02.cluster.local ha-conf-k8s-02
168.1.3 ha-conf-k8s-03.cluster.local ha-conf-k8s-03

注釈

Chabnge the Cluster names and IP addresses accordingly.

Create SSH key¶

リスト 2.7 Command¶

ssh-keygen -t rsa

Deploy the SSH key ( /root/.ssh/id_ras.pub ) in the cluster.

Install Kubespray¶

Install Kubespray using git clone.

リスト 2.8 Command¶

git clone https://github.com/kubernetes-sigs/kubespray.git -b release-2.23

cd kubespray/

pip3.9 install -r requirements.txt

If it outputs Successfully installed, Kubespray has been installed successfully.

2.3.2. Kubernetes cluster preparation¶

Follow the following steps for all the Kubernetes cluster environments.

Activating IPv4 forwarding¶

Change to Root user
リスト 2.9 Command¶
```
sudo su -
```

Rewrite /etc/sysctl.conf

Add the following line; net.ipv4.ip_forward=1

リスト 2.10 Command¶

vi /etc/sysctl.conf

リスト 2.11 sysctl.conf¶

# sysctl settings are defined through files in
# /usr/lib/sysctl.d/, /run/sysctl.d/, and /etc/sysctl.d/.
#
# Vendors settings live in /usr/lib/sysctl.d/.
# To override a whole file, create a new file with the same in
# /etc/sysctl.d/ and put new settings there. To override
# only specific settings, add a file with a lexically later
# name in /etc/sysctl.d/ and put new settings there.
#
# For more information, see sysctl.conf(5) and sysctl.d(5).
+net.ipv4.ip_forward=1

Install/Deactivate firewall

リスト 2.12 Command¶

dnf install firewalld

disable firewalld

stop firewalld

status firewalld

Deactivate SELinux

Confirm current status

リスト 2.13 Command¶

getenforce

The next step can be skipped if it says "Disabled".

Configure the SELINUX=disabled option

リスト 2.14 Command¶

vi /etc/selinux/config

リスト 2.15 sysctl.conf¶

# This file controls the state of SELinux on the system.
# SELINUX= can take one of these three values:
#       enforcing - SELinux security policy is enforced.
#       permissive - SELinux prints warnings instead of enforcing.
#       disabled - No SELinux policy is loaded.
+SELINUX=disabled
# SELINUXTYPE= can take one of these two values:
#       targeted - Targeted processes are protected,
#       mls - Multi Level Security protection.
SELINUXTYPE=targeted

|Reboot the system after finishing configuring the settings.

リスト 2.16 Command¶

reboot

Check that it says "Disabled".

リスト 2.17 Command¶

getenforce

2.3.3. Install Kubernetes¶

In the Ansible execution environment, follow the following steps to install Kubernetes to the Kubernetes cluster environments.

Create hosts.yml¶

The Kubernetes clusters are created based on the contents of the hosts.yml file.

First, follow the steps below to create the hosts.yml file.

Change to Root user
リスト 2.18 Command¶
```
sudo su -
```
Change the directory to the git cloned Kubespray folder.
リスト 2.19 Command¶
```
cd kubespray/
```
Copy the sample inventory file.
リスト 2.20 Command¶
```
cp -rfp inventory/sample inventory/k8s_cluster
```
Configure the IP variable for the Kubernetes clusters
リスト 2.21 Command¶
```
declare -a IPS=(192.168.1.1 192.168.1.2 192.168.1.3)
```

Create hosts.yml

リスト 2.22 Command¶

CONFIG_FILE=inventory/k8s_cluster/hosts.yml python3.9 contrib/inventory_builder/inventory.py ${IPS[@]}

Confirm hosts.yml
リスト 2.23 Command¶
```
cat inventory/k8s_cluster/hosts.yml
```

Edit the hosts.yml file¶

Replace the contents of the hosts.yml with the information that will create the Kubernetes clusters.

In this guide, we will configure the Kubernetes clustesr to work as Controle planes and work nodes.

リスト 2.24 hosts.yml¶

all:
  hosts:
    v2ha-k8s-node1:
      ansible_host: 192.168.1.1
      ip: 192.168.1.1
      access_ip: 192.168.1.1
    v2ha-k8s-node2:
      ansible_host: 192.168.1.2
      ip: 192.168.1.2
      access_ip: 192.168.1.2
    v2ha-k8s-node3:
      ansible_host: 192.168.1.3
      ip: 192.168.1.3
      access_ip: 192.168.1.3
  children:
    kube_control_plane:
      hosts:
        v2ha-k8s-node1:
        v2ha-k8s-node2:
        v2ha-k8s-node3:
    kube_node:
      hosts:
        v2ha-k8s-node1:
        v2ha-k8s-node2:
        v2ha-k8s-node3:
    etcd:
      hosts:
        v2ha-k8s-node1:
        v2ha-k8s-node2:
        v2ha-k8s-node3:
    k8s_cluster:
      children:
        kube_control_plane:
        kube_node:
    calico_rr:
      hosts: {}

Configure proxy¶

If the user needs to use a proxy, they must edit the file below.

inventory/k8s_cluster/group_vars/all/all.yml

Install Kubernetes¶

Execute Kubesparay and install Kubernetes to the Kubernetes cluster environments.

リスト 2.25 Command¶

ansible-playbook -i inventory/k8s_cluster/hosts.yml --become --become-user=root cluster.yml --private-key=~/.ssh/id_rsa -e "download_retries=10" | tee ~/kubespray_$(date +%Y%m%d%H%M).log

This step may take 20-30 minutes depending on the environment and the number of clusters.

Confirm Kubernetes environment¶

After the previous step has finished, connect to the created Kubernetes cluster environment and run the following command to check the control planes and worker nodes.

リスト 2.26 Command¶

kubectl get nodes

If the results displays something similar to the example below, you are finished.

リスト 2.27 Results¶

NAME             STATUS   ROLES           AGE     VERSION
v2ha-k8s-node1   Ready    control-plane   8m48s   v1.27.7
v2ha-k8s-node2   Ready    control-plane   7m28s   v1.27.7
v2ha-k8s-node3   Ready    control-plane   7m17s   v1.27.7

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