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Updating Ubuntu Hostname After Cloning a Disk

Step 1: Change the Hostname

Update the hostname using the hostnamectl command:

sudo hostnamectl set-hostname NEW_HOSTNAME

Step 2: Update /etc/hostname

Edit the file manually:

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How to Join a Node into a MicroK8s Cluster as a Worker

MicroK8s provides an easy way to create lightweight Kubernetes clusters. This guide explains how to join a new node as a worker in an existing MicroK8s cluster using the --worker flag.

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1. On the Control Plane (Primary Node)

Run the following command to generate a join token:

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How to Set Up NFS Server on Ubuntu

Install NFS Server

First, install the NFS kernel server:

sudo apt install nfs-kernel-server

Start the NFS service:

sudo systemctl start nfs-kernel-server.service

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How to re-generate K8s SSL Certificates on MicroK8s

Issue

You might encounter the following error when you the IP addresses is changed on the host machine:

Unable to connect to the server: x509: certificate is valid for <internal IPs>, not <external IP>

Solution

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Adding Users with Role Policy in Argo CD

Step 1: Login to Argo CD

You can log in to Argo CD or bash into the Argo CD pod running in Kubernetes:

argocd login <ARGOCD_SERVER> --username admin --password <ADMIN_PASSWORD>

Step 2: Create a User

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Fixing K8s Node UnHealthy after Re-boot Issue

Issue:

Nodes in the Kubernetes cluster may remain in an "Unhealthy" state on the control plane/master node after they are restarted. This problem occurs because the nf_conntrack module, which is essential for network connection tracking, is not automatically loaded on reboot.

Solution:

To ensure nodes reconnect properly after a restart, you need to make sure the nf_conntrack module is loaded at boot on all workers nodes thought this command;

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Fixing Network Driver Issues on Ubuntu 20.04

If you encounter missing network drivers when installing Ubuntu on new machines, you might notice that network cards are listed as (UNCLAIMED) when you execute the command:

lshw -c network

This indicates that your device requires Hardware Enablement (HWE).

About Hardware Enablement (HWE)

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Install Let's Encrypt SSL Certificate on Kubernetes Cluster (Microk8s)

Install Cert Manager

sudo microk8s kubectl apply -f https://github.com/jetstack/cert-manager/releases/download/v1.15.1/cert-manager.yaml

Create a Cluster Certiticate Issuer

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Allow Root User Access via SSH

1. Reset Ubuntu Root Password

Ensure you set a strong password:

sudo passwd root

2. Install OpenSSH Server and Client

Update the system and install both SSH components:

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Install Docker on Linux (Ubuntu)

To install Docker run the command:

curl -sSL https://get.docker.com/ | sudo sh

Check version if working correctly:

docker --version