Completek8s Classroomnotes 12/Aug/2023

Installing kubernetes using kube-spray

• kube-spray can help us installing k8s cluster using ansible
• input:
  • atleast 2 instances with ip addresses
  • user should have sudo permission on both instances
• Steps:
  • Ensure you have keypair in your local system ssh-keygen
  • Now create at least 3 vms with atleast 2 vcpu and 4 GB RAM
  • upload id_rsa from your laptop into master node
  • ensure connectivity is working as shown in the class

Installation

• clone kube-spray cd ~ && git clone https://github.com/kubernetes-sigs/kubespray.git
• ensure apt packages are up to date sudo apt update
• install pip3 and venv

sudo apt install python3-venv python3-pip -y

• Install ansible Refer Here

cd ~
VENVDIR=kubespray-venv
KUBESPRAYDIR=kubespray
python3 -m venv $VENVDIR
source $VENVDIR/bin/activate
cd $KUBESPRAYDIR
pip3 install -U -r requirements.txt
ansible --version

• Update Ansible inventory file with inventory builder

cp -rfp inventory/sample inventory/mycluster
declare -a IPS=(10.0.0.4 10.0.0.5 10.0.0.6)
CONFIG_FILE=inventory/mycluster/hosts.yaml python3 contrib/inventory_builder/inventory.py ${IPS[@]}

• Review and change parameters under inventory/mycluster/group_vars

cat inventory/mycluster/group_vars/all/all.yml
cat inventory/mycluster/group_vars/k8s_cluster/k8s-cluster.yml

• Review generated inventory file

vi inventory/mycluster/hosts.yaml

• Now lets reset the cluster to remove unncessary components

ansible-playbook -i inventory/mycluster/hosts.yaml  --become --become-user=root reset.yml

• Now lets install kubernetes cluster using kube spray

ansible-playbook -i inventory/mycluster/hosts.yaml  --become --become-user=root cluster.yml

Exercise

• Find out what step 6 means Refer Here
• How to use kubectl from a different system like laptop in the case of kubeadm or kubespray ?

Role Based Access control (RBAC)

• In k8s you need to be authenticated before you are allowed to make a request to an API Resource.
• A cluster administrator has access to all resources and operations and is easiest way to operate with admin account, but sharing it with everyone poses security risk admin access for everyone
• RBAC defines policies for users, groups and processes by allowing and disallowing access to manage API resoruces.
• RBAC helps in implementing use-cases such as
  • Establishing a system for users with different roles to access set of k8s resources
  • Controlling process running in a Pod and Operations they can perform via k8s api
  • Limiting visibility of certain resources in namespaces
• Three building blocks of k8s RBAC
  • Subject: The user or process that wants to access a resource
  • Resource: The k8s api resource (eg Pod, Deployment, StatefulSet, …)
  • Verb: The Operation that can be performed on a resource
    
• note: kubectl auth can-i helps in finding whether you have access on resource to perform some operation Refer Here