English on Ayoub's Blog

Day 0 - linux primitives that make k8s possible

Thu, 19 Mar 2026 23:33:57 +0100

so what what happen when we install k8s ?

when we install k8s actually we get this processes we can separate them logically (they are not separated physically like not namespaces or something) they are just have a different roles :

Our Physical Machine (or VM)
│
├── Control plan processes ← just Linux processes
│ ├── etcd (a process)
│ ├── kube-apiserver (a process)
│ ├── kube-scheduler (a process)
│ └── kube-controller-manager (a process)
│
└── Worker Node processes ← also just Linux processes
 ├── kubelet (a process)
 ├── kube-proxy (a process)
 └── containerd (a process)

so what is a node ?

a node it’s just a machine (VM/ cloud instance) that k8s know about it and can schedule a work onto it

etcd

Thu, 19 Mar 2026 23:31:51 +0100

setup

i have 3 VMs: vm1, vm2 and vm3

Node	IP Address
node1	172.31.253.147
node2	172.31.250.205
node3	172.31.253.194

step1: Install etcd on ALL 3 Nodes and create the data dir

let’s verify the version and create the data directory

step2: Create the etcd systemd Service

we do the same thing for other VMs changing just the ip add for example for node1

Containerd under the hood

Fri, 06 Mar 2026 00:00:47 +0100

Phase 1: runc Raw — Zero Tooling

so what we’ll do in this phase is exactly what containerd does internally

me (manually) vs containerd (automatically) ─────────────────────────────────────────────────────────

Create rootfs → pulls image layers
Write config.json → generates OCI bundle
Call runc run → calls runc via shim
Watch cgroups appear → same thing happens

first i installed containerd so it’s automatically we can see that we have runc but not crun, (so the default OCI implementation in containerd is runc)

containerd vs OCI, and the k8s architecture

Wed, 04 Mar 2026 00:00:00 +0000

what is the different between containerd and OCI (open container initiative)

writing …

k8s architecture

thanks @djalal for explications <3 writing …

Docker runtime stack, build cache and volumes

Tue, 03 Mar 2026 23:52:59 +0100

Docker runtime stack

1- docker cli

translate commands to rest api and send it over unix socket


docker run ngnix ===> POST /container/create {"Image":"nginx:latest", ....}

===> sent to: /var/run/docker.sock

so we can talk to dockerd with it


curl --unix-socket /var/run/docker.sock http://localhost/containers/json

2- dockerd

it’s an orchestrator

manage images (pull, build)
manage volume (create net, mount)
manage network (bridge creation, port mapping)

docker run delegated to containerd not here !!

Container Filesystem

Sun, 08 Feb 2026 23:56:04 +0100

Crafting My Own Storage Engine-Part 01: Java I/O Fundamentals

Tue, 13 Jan 2026 19:37:47 +0100

The “Page” Abstraction

so the ByteBuffer acts like a staging area where we serialize our Java objects (the Page object) into raw bytes and keep them in RAM using methods like putInt

and after that, we need to persist the data to disk — meaning we write those bytes into a file so the data survives after the program stops

so we have one large file, and since all pages have a fixed size, if we want to write the data for pageId = 14, we simply compute the offset 4096 * 14 and write the buffer at that position using the write method

Contains Duplicate (LeetCode 217)

Thu, 11 Dec 2025 00:42:08 +0100

Contains Duplicate (LeetCode 217)

the link of the problem here

Given an integer array nums, return true if any value appears at least twice in the array, and return false if every element is distinct.

Example 1: Input: nums = [1,2,3,1] Output: true Explanation: The element 1 occurs at the indices 0 and 3.

Example 2: Input: nums = [1,2,3,4] Output: false Explanation: All elements are distinct. Example 3: Input: nums = [1,1,1,3,3,4,3,2,4,2] Output: true

Part 1 - Building a Mini Spring Framework (v0.1)-Dependency Injection Basics

Wed, 10 Dec 2025 23:14:46 +0100

The problem Spring solves

easy right ? let’s see :)

imagine you are building an e-commerce backend, and you have OrderService that needs to process payments

the naive approach is: inside the OrderService you write for example

PaymentProcess process = new PaypalService();

if your boss comes and says “we’re switching the contract from PayPal to Stripe” what do you have to do to your code?

The answer is use an interface

public interface PaymentProcess {
	void pay(double amount);
}

and the OrderService looks like

Fixing Flyway Database Connection Errors in Docker

Thu, 20 Nov 2025 12:19:05 +0100

Before reading this blog i suggest you have a quick look at how Docker Compose starts services especially how databases take time to initialize before they start accepting connections.

so basically, when you work with microservices, each service has its own database (in my case: patient-db, doctor-db…). and when Spring Boot starts, Flyway tries to run the migration scripts immediately.

But there is a problem:

Flyway is much faster than PostgreSQL.
PostgreSQL says: “I’m starting…”
Flyway says: “I want to connect now.”
PostgreSQL says: “Wait wait wait hold on…”
Flyway says: “Connection refused.”

COMPUTER NETWORKS AND THE INTERNET

Tue, 14 Oct 2025 21:59:25 +0200

Our devices like PC, smartphones … in the vocab of computer networks are called “hosts” or “end systems”.
the TCP and IP are the most important protocols in the computer networks that control the sending and receiving of information within the Internet
TCP: Transmission Control Protocol.
IP: Internet Protocol.

Collection Interfece

Tue, 14 Oct 2025 01:15:28 +0200

the collection interface extends Iterable interface from java.lang we have a method boolean add(E e) that return true if the collection changed (the elem e added) and false if not boolean addAdd(Collection < ? extends E> c) , that take a collection of type E of subtype of E and return true if the collection changed (all elm added)

So if you have a Collection<Animal> and another Collection<Dog>,
you can add the Dogs into the Animal collection because Dog extends Animal.

Create My Own JCF-week1

Sat, 11 Oct 2025 00:59:35 +0200

JCF: Java Collection Framework Hierarchy

_Bfore starting implementing JCF should you know the Iterable interface

1. Iterable

Iterable interface is a builtin interface in java it allow us using “for-each” loop thanks to Iterator method

let’s take an example if you work with arrays in java and suppose you create an new array

int[] arr = new Interger[]{1,2,3}

and you want to make the forEach loop like this for(int n : arr) => this will give you a compiler error

MicroServices With Go and kuber

Wed, 08 Oct 2025 08:45:00 +0200

coming soon :)

The OS Manages The Hardware

Wed, 17 Sep 2025 17:09:33 +0200

1) Layered view of a computer system

the os is a piece of software that is setting between the applications programs and the hardware

the role of the os is

Protect the hardware from misuse by runaway the applications
provide application with simple and uniform mechanisms

2) Abstractions provided by an operating system

files are abstraction for I/O devices virtual memory is an abstraction for the main memory + I/O devices Processes are abstraction for processor + main memory + I/O devices

Doubly Linked Lists

Mon, 08 Sep 2025 23:23:40 +0200

In this blog we’ll see how we can implementing a doubly linked list if you haven’t seen the Singly Linked List yet it’s better to check it here first, because the concept is almost the same with just a few changes.

the main difference is in the node itself this time a node referenced by the next node and the prev node as you can see in this image

let’s implemented in java

Leet-Code-Day001

Thu, 04 Sep 2025 23:34:00 +0200

you can see the problem here Merge Two Sorted Lists

The idea is that we have two sorted singly linked lists and we want a single merged linked list containing all the elements from the two original lists in sorted order like this:

before looking at the steps of the solution, let’s see the implementation of the singly linked list with int value (you can see the generic version here Singularly Linked List )

Circularly Linked List

Thu, 04 Sep 2025 00:02:05 +0200

Before to read about circularly linked lists i suggest to go to read bit about Singly Linked List, to better understanding circularly linked lists(CLL)

so basically a CLL is a Singly linked list and instead of the its tail (last node of the list) point on null its point of the first element of the list (head). like this

Singly Linked List

Tue, 12 Aug 2025 00:00:00 +0000

Before you read this if you want a deep dive on Singly LinkedList and DSA with java in general please read the “Chapter 3. Fundamental Data Structures” p.122 by MICHEAL T.GOODRICH

1. Node

First let’s define a node, so a node it’s a data structure that can store an object and point to another node

like this

we can define it in java like

public class Node<E> {

 private E data;
 private Node<E> next;

 public Node(E data){
 this.data = data;
 this.next = null;
 }

 public E getData() {
 return data;
 }

 public void setData(E data) {
 this.data = data;
 }

 public Node<E> getNext() {
 return next;
 }

 public void setNext(Node<E> next) {
 this.next = next;
 }

 public String toString(){
 return "("+data+") =>(null)";
 }
}

As you can see in the code, the constructor of the Node initializes the next pointer to null, which is what we want.

Obsidian + Hugo + GitHub Pages Blog Setup Guide

Sun, 10 Aug 2025 00:00:00 +0000

Overview

This setup creates an automated blog workflow where you write in Obsidian, push to GitHub, and GitHub Actions automatically builds and deploys your Hugo site.

Phase 1: Local Setup

Step 1: Install Required Tools

Install Hugo

# Windows (using Chocolatey)
choco install hugo-extended

# macOS (using Homebrew)
brew install hugo

# Linux (using Snap)
sudo snap install hugo

Install Git (if not already installed)
- Download from git-scm.com
Install Obsidian