Linux Conquering Cloud: Kubernetes

Showing posts with label Kubernetes. Show all posts

Monday, April 10, 2023

Kubernetes(k8s) Sample Commands - 02

Following are a few of the kubectl commands for managing Kubernetes clusters:

kubectl get nodes -o=jsonpath='{XX}'

This command retrieves information about the nodes in the cluster using the jsonpath output format. Replace {XX} with the desired path.

kubectl get nodes -o=custom-columns=<Column name>

This command retrieves information about the nodes in the cluster using custom columns output format. Replace <Column name> with the desired column name

--sort-by=

This option is used to sort the output based on a specified field.

kubectl get node node01 -o json > /opt/outputs/node01.json

This command retrieves information about a specific node and saves it as a JSON file.

kubectl get nodes -o jsonpath='{.items[*].status.nodeInfo.osImage}' > /opt/outputs/nodes_os.txt

This command retrieves the OS image of all the nodes in the cluster and saves it in a text file.

kubectl config view --kubeconfig=my-kube-config -o jsonpath="{.users[*].name}" > /opt/outputs/users.txt

This command retrieves the names of all users in the kubeconfig file and saves it in a text file.

kubectl get pv --sort-by=.spec.capacity.storage > /opt/outputs/storage-capacity-sorted.txt

This command retrieves the capacity of all persistent volumes and sorts the output by storage capacity.

kubectl config view --kubeconfig=my-kube-config -o jsonpath="{.contexts[?(@.context.user=='aws-user')].name}" > /opt/outputs/aws-context-name

This command retrieves the context name for a specific user in the kubeconfig file.

kubectl run test-nslookup --image=busybox:1.28 --rm -it --restart=Never -- nslookup nginx-resolver-service

This command creates a pod named test-nslookup and runs a DNS lookup on nginx-resolver-service.

kubectl run test-nslookup --image=busybox:1.28 --rm -it --restart=Never -- nslookup nginx-resolver-service > /root/CKA/nginx.svc

This command creates a pod named test-nslookup and redirects the output of the DNS lookup to a file.

K get nodes -o jason | jq -c paths |grep type

This command retrieves the paths of all fields in the node objects in the cluster that contain the word "type".

kubectl create deployment --image=nginx nginx --replicas=4 --dry-run=client -o yaml > nginx-deployment.yaml

This command creates a deployment named nginx with 4 replicas and saves the deployment manifest as a YAML file. The --dry-run=client flag is used to simulate the deployment without actually creating it.

Monday, August 8, 2022

PodMan

Podman is a container engine that allows you to create, run, and manage containers on a Linux host. It is similar to other container runtimes such as Docker, Rocket, Drawbridge, and LXC. Podman has a command-line interface that is similar to Docker, making it easy to switch from Docker to Podman.

If you're new to Podman, here are some basic commands that will help you get started:

podman login -u username -p password registry.access.redhat.com: Log in to a container registry.
podman pull <image-name>: Download a container image.
podman ps -a: List all containers, both running and stopped.
podman search <image-name>: Search for a container image.
podman images: List all container images.
podman run <image-name> echo 'Hello world!': Run a container with a specific image and command.
podman run -d -p 8080 httpd: Run a container with an image in the background and map port 8080.
podman port -l: Display the port details of the last used container.
podman run -it ubi8/ubi:8.3 /bin/bash: Run a container and enter into its bash shell.
podman run --name MySQL-custom -e MYSQL_USER=Ruser -e MYSQL_PASSWORD=PASS -e MYSQL_ROOT_PASSWORD=PASS -d MySQL: Run a container with a custom name and environment variables.
podman ps --format "{{.ID}} {{.Image}} {{.Names}}": List containers with custom output formatting.

In Podman, you can create both root and rootless containers. Root containers run with elevated privileges, while rootless containers run without elevated privileges and are isolated from the host system.

Here are some commands to create and manage root and rootless containers using Podman:

sudo podman run --rm --name asroot -ti httpd /bin/bash: Run a container as root.
podman run --rm --name asuser -ti httpd /bin/bash: Run a container as a regular user.
podman run --name my-httpd-container httpd: Run a container with a custom name.
podman exec httpd-container cat /etc/hostname: Run a command inside a running container.
podman stop my-httpd-container: Stop a running container.
podman kill -s SIGKILL my-httpd-container: Send a custom kill signal to a running container.
podman restart my-httpd-container: Restart a container that has been stopped.
podman rm my-httpd-container: Remove a container.
podman rm -a: Remove all containers.
podman stop -a: Stop all running containers.
podman exec mysql /bin/bash -c 'mysql -uuser1 -pmypa55 -e "select * from items.Projects;"': Run a command inside a running container.

Sharing a local directory with a container is a common task in containerization. Podman makes this process simple by allowing you to mount a local directory to a container using the -v option.

Create a local directory with proper SELinux permissions

mkdir /home/student/dbfiles
podman unshare chown -R 27:27 /home/student/dbfiles
sudo semanage fcontext -a -t container_file_t '/home/student/dbfiles(/.*)?'
sudo restorecon -Rv /home/student/dbfiles
ls -ldZ /home/student/dbfiles

The mount the path with -v location_in_local:location_in_container

podman run -v /home/student/dbfiles:/var/lib/mysql rhmap47/mysql
podman unshare chown 27:27 /home/student/local/mysql

Port management

Port management is an important aspect of containerization, and Podman provides a simple way to manage ports for containers. You can use the -p option to map ports between the container and the host system.

Here's an explanation of the commands used in port management with Podman:

podman run -d --name apache1 -p 8080:8080 httpd: Run a container with the httpd image, map port 8080 on the host system to port 8080 in the container, and name the container apache1.
podman run -d --name apache2 -p 127.0.0.1:8081:8080 httpd: Run a container with the httpd image, map port 8081 on the localhost interface of the host system to port 8080 in the container, and name the container apache2.
podman run -d --name apache3 -p 127.0.0.1::8080 httpd: Run a container with the httpd image, map a random port on the localhost interface of the host system to port 8080 in the container, and name the container apache3.

podman port apache3: Display the port details of the apache3 container.

In the first command, the -p option is used to map port 8080 on the host system to port 8080 in the container. This means that if you access port 8080 on the host system, you will be accessing the container's port 8080.

In the second command, the -p option is used to map port 8081 on the localhost interface of the host system to port 8080 in the container. This means that if you access port 8081 on the localhost interface of the host system, you will be accessing the container's port 8080.

In the third command, the -p option is used to map a random port on the localhost interface of the host system to port 8080 in the container. This means that a random port on the host system will be mapped to the container's port 8080.

The podman port command displays the port details of a container, including the mapping between the container's ports and the host system's ports.

By using these commands, you can easily manage ports for containers in Podman.

Podman Image Management

Podman is available on a RHEL host with the following entry in /etc/containers/registries.conf file:

[registries.search]
registries = ["registry.redhat.io","quay.io"]

podman save [-o FILE_NAME] IMAGE_NAME[:TAG]: Save an image to a file. You can use the -o option to specify the output file name. For example, podman save -o mysql.tar quay.io/mysql:latest saves the quay.io/mysql:latest image to a file named mysql.tar.
podman load [-i FILE_NAME]: Load an image from a file. You can use the -i option to specify the input file name. For example, podman load -i mysql.tar loads the mysql.tar file and creates an image.
podman rmi [OPTIONS] IMAGE [IMAGE...]: Remove one or more images. You can use the -a option to remove all images. For example, podman rmi -a removes all images.
podman commit [OPTIONS] CONTAINER [REPOSITORY[:PORT]/]IMAGE_NAME[:TAG]: Create a new image from a container. You can use the -a option to specify the author name. For example, podman commit -a 'Your Name' httpd httpd-new creates a new image named httpd-new from the httpd container with author name Your Name.

Here's an explanation of the few of the Podman commands:

podman diff container-name: This command shows the differences between the container's current state and its original state at the time of its creation. The diff subcommand tags any added file with an A, any changed ones with a C, and any deleted file with a D. This is useful for troubleshooting issues or for auditing the changes made to a container.
podman tag [OPTIONS] IMAGE[:TAG] [REGISTRYHOST/][USERNAME/]NAME[:TAG]: This command is used to tag an image with a new name or repository. You can use the [REGISTRYHOST/][USERNAME/] part to specify the registry where you want to tag the image. For example, podman tag mysql-custom devops/mysql tags the mysql-custom image with the name devops/mysql.
podman rmi devops/mysql:snapshot: This command removes an image with the specified name and tag. For example, podman rmi devops/mysql:snapshot removes the devops/mysql image with the snapshot tag.
podman push [OPTIONS] IMAGE [DESTINATION]: This command pushes an image to a specified destination, such as a container registry. You can use the [DESTINATION] part to specify the registry where you want to push the image. For example, podman push quay.io/bitnami/nginx pushes the quay.io/bitnami/nginx image to the specified registry.

Friday, August 5, 2022

Kubernets Components

Kubernetes, also known as K8s, is a popular container orchestration tool that automates the deployment, scaling, and management of containerized applications. The Kubernetes environment is made up of several core components that work together to provide a scalable and robust container management system. While there are other optional components available, these core components are essential to the Kubernetes environment.

Kubernetes API Server: The Kubernetes API server acts as the primary management hub for the Kubernetes cluster. It exposes the Kubernetes API, which is used by other components to interact with the cluster. The API server validates and processes API requests, and updates the cluster state accordingly.
etcd: etcd is a distributed key-value store that stores the configuration data and state of the Kubernetes cluster. It provides a reliable and consistent data store that is used by the Kubernetes API server and other components to store and retrieve data.
kubelet: The kubelet is responsible for managing and monitoring individual nodes (worker machines) in the Kubernetes cluster. It communicates with the Kubernetes API server to ensure that the containers running on a node are healthy and running as intended.
kube-proxy: The kube-proxy is responsible for managing network communication within the Kubernetes cluster. It sets up and maintains network routes and load balancing for Kubernetes services running on the cluster.
Kubernetes Scheduler: The Kubernetes scheduler is responsible for scheduling workloads (containers) onto worker nodes in the cluster. It considers factors such as resource availability, workload constraints, and affinity rules to make optimal scheduling decisions.

Data Plane: Worker Nodes, Where the Pods or Containers with workload run
Control Plane: Master Node, where the k8s components run

Following are the Components of the Control Plane

Apiserver

Apiserver service act as the connection between all the components in the Control Plane and Data Plane
Orchestrating all operations in the cluster
Expose the K8s API which end users use for operation and monitoring
Collect data from Kubelet for Monitoring
Authenticates - Validates - retrieve data
Give data or do the operations with data
Pass data to kubelet to perform operations in the Worker node

etcd

etcd service is mainly used for the storage of all the details. Etcd is basically a key-value pair data store.
Store Data not limited to the following details

Registry
Nodes
Pods
Config
Secrets
Accounts
Roles
-- other components as well

Kube scheduler

Identify the right worker nodes in which containers can be deployed and give data back to API Servers, then kubelet get data from API server and deploys the container.
Keeps on monitoring the API Server for operations
Identify the right worker node for mentioned operation and give it back to API Server
Filter nodes
Ranks nodes :

Resource requirements, resources left after container placement
Taints and Tolerations
Node Selectors/Affinity
Labels and Selectors
Resource limits
Manual Scheduling
Daemon Sets
Multiple Schedulers
Scheduler Events

Kube-controller-Manager

Watch Status
Remediate Situations
Monitor the state of the system and try to bring it to the desired state

Following are the Components of the Data Plane

Kubectl

Client used to connect to API Server

Kubelet

Agent runs on each Worker nodes
Listens to the Kube APIs and Performs the Operation
give back data to Kube API Server for monitoring of operation

Kube-proxy

Enable communication between services in Worker nodes
Pod-Network

by Default All pods connect to each other

Create Iptable rules to allow communication between pods and services

Friday, January 28, 2022

Kubernetes(k8s) with Containerd Using Ansible Over Ubuntu Machines

Kubernetes is a popular container orchestration system that provides a powerful platform for managing containerized applications. Containerd is a lightweight, yet powerful container runtime that provides the underlying infrastructure for many Kubernetes deployments. In this, we can see how to set up Kubernetes with Containerd using Ansible over Ubuntu machines.

Environment

Ubuntu VM's running on Vmware
K8s with Containerd Runtime

User Creation

Asks for the User Name which has to be created
Create's the user
Adds a dedicated Sudo entry
Setting up Password less sudo for user
Copy the local uses ssh key to server for password less auth
Print the details
Updates the System
Steps added for the Package Cleaning as well.

- hosts: all
  become: yes

  vars_prompt:
   - name: "new_user"
     prompt: "Account need to be create in remote server."
     private: no

  tasks:
    - name: creating the user {{ new_user }}.
      user:
        name: "{{ new_user }}"
        createhome: yes
        shell: /bin/bash
        append: yes
        state: present  

    - name: Create a dedicated sudo entry file for the user.
      file:
        path: "/etc/sudoers.d/{{ new_user }}"
        state: touch
        mode: '0600'
        
    - name: "Setting up Sudo without Password for user {{ new_user }}."
      lineinfile:
        dest: "/etc/sudoers.d/{{ new_user }}"
        line: '{{ new_user }}  ALL=(ALL) NOPASSWD: ALL'
        validate: 'visudo -cf %s'

    - name: Set authorized key for user copying it from current {{ new_user }}  user.
      authorized_key:
         user: "{{ new_user }}"
         state: present
         key: "{{ lookup('file', lookup('env','HOME') + '/.ssh/id_rsa.pub') }}"

    - name: Print the created user.
      shell: id "{{ new_user }}"
      register: new_user_created
    - debug:
        msg: "{{ new_user_created.stdout_lines[0] }}"

    
    - name: Remove Docker packages
      apt:
        name: docker-ce docker-ce-cli containerd.io
        state: absent
        purge: yes

    - name: Remove Docker directories
      file:
        path: "{{ item }}"
        state: absent
      with_items:
        - /etc/docker
        - /var/lib/docker
        - /var/run/docker.sock

    - name: Remove containerd packages
      apt:
        name: containerd
        state: absent
        purge: yes

    - name: Remove containerd directories
      file:
        path: "{{ item }}"
        state: absent
      with_items:
        - /etc/containerd
        - /var/lib/containerd
        
    - name: "Update cache & Full system update"
      apt:
        update_cache: true
        cache_valid_time: 3600
        force_apt_get: true

Package Installation in Master and Worker Nodes

Copy the local host files to all the server for name resolution
update the hostnames of the machines based on the names in host file
Temporary Swap off
Swap off in fstab
Create a empty file for containerd module.

Configure module for containerd.

Create a empty file for kubernetes sysctl params.

Configure sysctl params for Kubernetes.

Apply sysctl params without reboot

Installing Prerequisites for Kubernetes

Add Docker’s official GPG key

Add Docker Repository

Install containerd.

Configure containerd.

Creating containerd Config file

Enable containerd service, and start it.

Add Google official GPG key

Add Kubernetes Repository

Installing Kubernetes Cluster Packages.

Enable service kubelet, and enable persistently

Reboot all the Kubernetes nodes.

- hosts: "master, workers"
  remote_user: ansible
  become: yes
  become_method: sudo
  become_user: root
  gather_facts: yes
  connection: ssh
  
  tasks:
   - name: Copying the host file
     copy:
      src: /etc/hosts
      dest: /etc/hosts
      owner: root
      group: root

   - name: "Updating hostnames"
     hostname:
      name: "{{ new_hostname }}"

   - name: Make the Swap inactive
     command: swapoff -a

   - name: Remove Swap entry from /etc/fstab.
     lineinfile:
       dest: /etc/fstab
       regexp: swap
       state: absent

   - name: Create a empty file for containerd module.
     copy:
       content: ""
       dest: /etc/modules-load.d/containerd.conf
       force: no

   - name: Configure module for containerd.
     blockinfile:
       path: /etc/modules-load.d/containerd.conf 
       block: |
            overlay
            br_netfilter

   - name: Create a empty file for kubernetes sysctl params.
     copy:
       content: ""
       dest: /etc/sysctl.d/99-kubernetes-cri.conf
       force: no

   - name: Configure sysctl params for Kubernetes.
     lineinfile:
       path: /etc/sysctl.d/99-kubernetes-cri.conf 
       line: "{{ item }}"
     with_items:
       - 'net.bridge.bridge-nf-call-iptables  = 1'
       - 'net.ipv4.ip_forward                 = 1'
       - 'net.bridge.bridge-nf-call-ip6tables = 1'

   - name: Apply sysctl params without reboot.
     command: sysctl --system

   - name: Installing Prerequisites for Kubernetes
     apt: 
       name:
         - apt-transport-https
         - ca-certificates
         - curl
         - gnupg-agent
         - vim
         - software-properties-common
       state: present

   - name: Add Docker’s official GPG key
     apt_key:
       url: https://download.docker.com/linux/ubuntu/gpg
       state: present
       
   - name: Add Docker Repository
     apt_repository:
       repo: deb [arch=amd64] https://download.docker.com/linux/ubuntu bionic stable
       state: present
       filename: docker
       update_cache: yes

   - name: "Update cache & Full system update"
     apt:
        update_cache: true
        upgrade: dist
        cache_valid_time: 3600
        force_apt_get: true

   - name: Install containerd.
     apt: 
       name:
         - containerd.io
       state: present

   - name: Configure containerd.
     file:
       path: /etc/containerd
       state: directory

   - name: Enable containerd service, and start it.
     systemd: 
       name: containerd
       state: restarted
       enabled: yes
       daemon-reload: yes

   - name: Add Google official GPG key
     apt_key:
       url: https://packages.cloud.google.com/apt/doc/apt-key.gpg
       state: present

   - name: Add Kubernetes Repository
     apt_repository:
       repo: deb http://apt.kubernetes.io/ kubernetes-xenial main 
       state: present
       filename: kubernetes
       mode: 0600

   - name: "Update cache & Full system update"
     apt:
        update_cache: true
        upgrade: dist
        cache_valid_time: 3600
        force_apt_get: true

   - name: Installing Kubernetes Cluster Packages.
     apt: 
       name:
         - kubeadm
         - kubectl
         - kubelet
       state: present

   - name: Enable service kubelet, and enable persistently
     service: 
       name: kubelet
       enabled: yes

   - name: Reboot all the kubernetes nodes.
     reboot:
      msg: "Reboot initiated by Ansible"
      connect_timeout: 5
      reboot_timeout: 3600
      pre_reboot_delay: 0
      post_reboot_delay: 30
      test_command: whoami

Master Configuration

Pulls all needed images
Reset Kubeadm if its already configured
Initialize K8s cluster
Create Directory for Kube config file in master
Create a local kube config file in master
Copy the kube config file to ansible local server
Genarates the Kube toke for workers and stores it
Copy the token to master's tmp directory
Copy the toke to ansible local tmp direcotry
Initialize the pod network with fannel
Copy the output to mater file
Copy the output to ansible local server

- hosts: master
  remote_user: ansible
  become: yes
  become_method: sudo
  become_user: root
  gather_facts: yes
  connection: ssh
  tasks:

  - name: Pulling images required for setting up a Kubernetes cluster
    shell: kubeadm config images pull

  - name: Resetting kubeadm
    shell: kubeadm reset -f
    register: output

  - name: Initializing Kubernetes cluster
    shell: kubeadm init --apiserver-advertise-address=$(ip a |grep ens160|  grep 'inet ' | awk '{print $2}' | cut -f1 -d'/') --pod-network-cidr 10.244.0.0/16 --v=5
    register: myshell_output

  - debug: msg="{{ myshell_output.stdout }}"

  - name: Create .kube to home directory of master server
    file:
       path: $HOME/.kube
       state: directory
       mode: 0755

  - name: Copy admin.conf to user's kube config to master server
    copy:
       src: /etc/kubernetes/admin.conf
       dest: $HOME/.kube/config
       remote_src: yes

  - name: Copy admin.conf to user's kube config to ansible local server
    become: yes
    become_method: sudo
    become_user: root
    fetch:
       src: /etc/kubernetes/admin.conf
       dest: /Users/rahulraj/.kube/config
       flat: yes
       
  - name: Get the token for joining the nodes with Kuberentes master.
    shell: kubeadm token create  --print-join-command
    register: kubernetes_join_command
  
  - debug:
     msg: "{{ kubernetes_join_command.stdout_lines }}"

  - name: Copy K8s Join command to file in master
    copy:
     content: "{{ kubernetes_join_command.stdout_lines[0] }}"
     dest: "/tmp/kubernetes_join_command"

  - name: Copy join command from master to local ansible server
    fetch:
      src: "/tmp/kubernetes_join_command"
      dest: "/tmp/kubernetes_join_command"
      flat: yes

  - name: Install Pod network
    shell: kubectl apply -f https://raw.githubusercontent.com/coreos/flannel/master/Documentation/kube-flannel.yml
    register: myshell_output

  - name: Copy the output to master file
    copy:
     content: "{{ myshell_output.stdout }}"
     dest: "/tmp/pod_network_setup.txt"

  - name: Copy network output from master to local ansible server
    fetch:
      src: "/tmp/pod_network_setup.txt"
      dest: "/tmp/pod_network_setup.txt"
      flat: yes

Worker Configuration

Copy the token from ansible local file to worker nodes
Reset the kubeadm
Join the Worker node to Master by running the command

- hosts: workers
  remote_user: ansible
  become: yes
  become_method: sudo
  become_user: root
  gather_facts: yes
  connection: ssh
  tasks:

   - name: Copy token to worker nodes.
     become: yes
     become_method: sudo
     become_user: root
     copy:
       src: /tmp/kubernetes_join_command
       dest: /tmp/kubernetes_join_command
       mode: 0777 
   - name: Resetting kubeadm
     shell: kubeadm reset -f
     register: output

   - name: Join the Worker nodes with the master.
     become: yes
     become_method: sudo
     become_user: root
     command: sh /tmp/kubernetes_join_command
     register: joined_or_not
   - debug:
      msg: "{{ joined_or_not.stdout }}"

K8s should be up with the worker nodes now.

Friday, January 21, 2022

Setting up MetalLB Load Balancer with Kubernetes k8s.

When we are deploying the Kubernetes in the local development environment and if we need to publish the services through load balancer services then Metallb load balancer is one of the easiest solutions we can use. All we need is a set of IP range from our network which metal lb can use.

Following are the k8s configurations that need to be applied on the cluster.

Below is the config map which mentions the IPs which can be used for the load balancers.

apiVersion: v1
kind: ConfigMap
metadata:
  namespace: metallb-system
  name: config
data:
  config: |
    address-pools:
    - name: default
      protocol: layer2
      addresses:
      - 172.16.2.80-172.16.2.90

Below is the ansible-playbook I used to deploy the metal load balancer on the k8s cluster.

Initialize the master with Metallb Clusters
Copy the metallb Configuration to master
Kube apply the configuration on master.

- hosts: master
  remote_user: ansible
  become: yes
  become_method: sudo
  become_user: root
  gather_facts: yes
  connection: ssh
  tasks:
  - name: Initializing Metallb cluster
    shell: kubectl apply -f https://raw.githubusercontent.com/google/metallb/v0.8.3/manifests/metallb.yaml
    register: myshell_output

  - name: Copying the Metallb config file
    copy:
     src: /Users/rahulraj/workspace/vmware-ansible/k8s/playbook/metallb-congif.yml
     dest: $HOME/metallb-congif.yml


  - name: Configuring Metallb cluster
    shell: kubectl apply -f $HOME/metallb-congif.yml
    register: myshell_output

For testing it we shall deploy a sample Nginx and expose it through load balancer type services.

k create deployment nginx-deployments --image=nginx --replicas=3 --port=80
k expose deployment nginx-deployments --port=80 --target-port=80 --type=LoadBalancer

Output should be like following

kubectl get svc

NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE

kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 25h

nginx-deployments LoadBalancer 10.100.137.154 172.16.2.80 80:30973/TCP 13h

Thursday, January 20, 2022

Kubernetes(k8s) With Ansible Over Ubuntu Machines with Docker

Kubernetes(k8s) is a popular container orchestration system that provides a powerful platform for managing containerized applications. Docker is a lightweight, yet powerful container runtime that provides the underlying infrastructure for many Kubernetes deployments. In this, we can see how to set up Kubernetes with Docker using Ansible over Ubuntu machines.