Ayman Bagabas


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© 2019 Ayman Bagabas

Dynamic DNS using DDclient

16 Feb 2019 0 Comments

DDclient is a service used to update dynamic DNS entries on many services. It is useful if you need a DDNS client that can work with pretty much any DNS service. Most distributions provide DDclient in their official repositories. It is available on Debian-based systems, Fedora, Archlinux, and many more.

In my case, I need DDclient for my NextcloudPi server that runs on a Raspberry Pi 3B hooked up to a storage device. This server gives me access to my files anywhere anytime as long as it has a working internet connection. I’m using a free DNS service from Dynu and in their website, they go in details of how you would set up dynamic DNS using DDclient. It turns out that they use a dyndns2 protocol by www.dyndns.com to provide this service.

Now after installing DDclient, the client can configure it under /etc/ddclient.conf where you can set the update interval, server address (in this case dynu.com), username and password, etc.

use=web, web=checkip.dynu.com/, web-skip='IP Address'

As you can see I’m using dynu.com server. Different DNS services would have different configurations.

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Writing a Chip-8 emulator

17 Sep 2018 0 Comments

If you ever played retro games on modern computers, then you probably know what an emulator is. Chip-8 is an interpreted programming language that was created originally by Joseph Weisbecker. Chip-8 programs get interpreted by a virtual machine. It offers a very simple monochrome graphics and uses a 4Kb of memory. It has the “8” part because all the system’s components, like CPU registers, have a size of 8 bits or 1 byte.

What is an Emulator?

The idea of an emulator is the same across any operating system. You basically try to translate the instructions of one system to another. The process of translation is done in three main parts:

  • Fetching opcodes
  • Decoding opcodes
  • Executing opcodes

These three steps happen in the CPU which is the main component of a system. The first step is to read operation codes from the program, then the CPU tries to decode these codes and then executes them accordingly.


Space Invaders

Before you get very excited, you really have to understand how the system works and behaves. Get familiar with your binary and hexadecimal conversions. A hex viewer may come handy when debugging a program.

CPU and Memory

Chip-8 is a simple system that has 16 CPU registers, each takes information up to 8 bits (1 byte). The program counter, I register, opcode placeholder, and a stack pointer, all have a size of 16 bits (2 bytes). Memory is a 4Kb memory where the first 512Kb is reserved for the interpreter which, this makes most programs written for the Chip-8 start at location 512. A minimal of 16 level stack pointer is required and it is used to store return locations from the program counter register.


There are two timers both countdown from 60 to 0. Delay timer is used for program events and its value can be set and read. And a sound timer which plays a beep whenever it reaches 0. After every operation execution, both timers get subtracted by 1.


The Chip-8 uses 16 keys of input, (0x0-0xF) which are usually mapped to:

1 2 3 C        1 2 3 4
4 5 6 D   --\  Q W E R
7 8 9 E   --/  A S D F
A 0 B F        Z X C V

Usually ‘2’, ‘4’, ‘8’, and ‘6’ are used for directions.


The Chip-8 has a 32x64 pixels monochrome display. It draws graphics on the screen using sprites. “A sprite is a group of bytes which are a binary representation of the desired picture.” And they may take up to 15 bytes. Chip-8 provides a set of predefined sprites for representing hexadecimal digits from 0 to F. For example:

  "1" |	Binary   | Hex
  *   | 00100000 | 0x20
 **   | 01100000 | 0x60
  *   | 00100000 | 0x20
  *   | 00100000 | 0x20
 ***  | 01110000 | 0x70

  "F" | Binary   | Hex
****  | 11110000 | 0xF0
*     | 10000000 | 0x80
****  | 11110000 | 0xF0
*     | 10000000 | 0x80
*     | 10000000 | 0x80

These sprites should be stored in the reserved interpreter area 0-512 of memory.


Start with the big picture, how does your computer works? After you boot your computer it starts initializing components and devices. This includes inputs, outputs, graphics, CPU, etc. Then it loads the system and starts executing instructions sequentially. The main loop should look something like this:

#include // Chip-8 system
#include // Input
#include // Graphics

int main(int argc, char **argv) {


    while(systeIsRunning) {
        // Execute instruction

        // Refresh display if flag is set
        if (drawFlag)
        // Play beep if flag is set
        if (playSound)

        // Set input and set keys states
    return 0;

Chip-8 should implement ways to load and execute instructions:

void initChip8() {
    // initialize system
    // memory
    // registers
    // stack
    // graphics

void loadROM(file) {
    // read file into memory
    // starting from location 512Kb
    // or 0x200 in hex

void executeOP() {
    // fetch opcode
    opcode = (memory[pc] << 8) + memory[pc + 1];
    // decode opcode
    switch (opcode & 0xF000) {
        // execute opcode
        case 0x0:
            if (opcode == 0x00E0)
            elseif (opcode == 0x00EE)
                // return from subroutine
        case 0x1:
        case 0xF:

    // timers
    if (delay_timer > 0)
    if (sound_timer > 0) {
        if (sound_timer == 1)

Input and graphics depend on the libraries you will be using. I went with SDL2 for these two since it is cross-platform, very well known, and has a lot of documentation. You can refer to my Chip-8 implementation here.

What next?

Well, I really learned a lot from this project. Next, I want to extend this project to have a terminal based UI using ncurses. Or maybe work on a more complex system like the NES?


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Arch Linux on Matebook X Pro

23 Jul 2018 0 Comments

Recently, I got a new laptop, Huawei Matebook X Pro. It has an i7 8th Gen. Intel CPU, 16Gib of RAM, 512Gib of SSD storage, Nvidia MX150 GPU with 2Gib of DRAM, and a beautiful HiDPI and touchscreen. It also comes with a fingerprint sensor. The first thing I did was installing Arch Linux, because well I am a Linux user! In the end, everything was working properly except:

  1. Two out of four speakers. See UPDATE1 down below
  2. The fingerprint sensor.
  3. Some keys in the Fn row. See UPDATE2

The installation was very straightforward and like every other Arch Linux installation process. I followed their installation guide. After the installation is complete, everything was working properly except for some minor issues.


First, disable secure boot from the BIOS menu by pressing F2 while booting. Then have your Arch Linux installation media ready, then you can access the boot menu by holding F12 while booting. Once you boot into Arch Linux live boot image, you will notice that the font is too small, you can change that to use a large font with setfont latarcyrheb-sun32, or you could use any other font you like.

Multi-lib repositories

You probably want to enable multi-lib repos to support 32-bit software. Just uncomment that in /etc/pacman.conf or add the following:

Include = /etc/pacman.d/mirrorlist


I used Grub for the bootloader. Obviously, you want to use Grub for UEFI systems. For the ESP location, I had mine set to /boot/efi just to follow other Linux distors approach. Because of the HiDPI screen that comes with this laptop, Grub would very tiny to see, a quick fix is to set the GRUB_GFXMODE variable to something like 1600x1200x32. The available values can be fetched from Grub command line by executing videoinfo. Edit your /etc/default/grub file to include these lines:


If you are dual-booting you should install the package os-prober to make Grub detect Windows partitions. Don’t forget to regenerate grub.cfg using:

# grub-mkconfig -o /boot/grub/grub.cfg

After Installation

Because I have a dual-boot setup with Windows, I ran into a little problem after partitioning Windows partition. However, it was easily fixed using ntfs-3g package which includes the tool ntfsfix. After you complete the installation and boot into Arch, just run the tool with -b to fix bad sectors and -d to clear dirty flag:

# ntfsfix -b -d /dev/nvme0n1p3

In my case, my Windows partition was /dev/nvme0n1p3, you should change that based on your partition name. You can use lsblk or blkid to list all your partitions.

AUR helper

One of Arch Linux beauties is AUR, where you can easily get any Linux package installed with ease. I used the tool aurman which is IMO one of the safest ones out there. Here is the full list of AUR helpers. To install aurman:

$ git clone https://aur.archlinux.org/aurman.git
$ cd aurman
$ makepkg -si

Desktop Environment

Since this device comes with a touch-enabled and HiDPI screen, I decided to go with Gnome because it supports these two things pretty well.

# pacman -S gnome gnome-extra

This would automatically install Gnome with Wayland. Wayland doesn’t require any further configuration or drivers.

Nvidia driver & Bumblebee

The MBXP comes with Intel UHD Graphics 620 and NVIDIA Geforce MX150. If you are planning to use the Nvidia card for gaming, rendering, or anything your best two options are using Prime technology with Nouveau (open source NVIDIA driver), or use NVIDIA proprietary driver with Bumblebee. I decided to go with the later because it offers better performance. Install Bumblebee

# pacman -S bumblebee bbswitch nvidia mesa acpi_call lib32-virtualgl lib32-nvidia-utils

Enable Bumblebee service and add user to Bumblebee group:

# systemctl enable bumblebeed.service
# gpasswd -a $USER bumblebee

You probably need to Enable NVIDIA card during shutdown to avoid issues with using it. Now we need to tell Bumblebee to use bbswitch for card switching. Edit /etc/bumblebee/bumblebee.conf to include this:


Sometimes Bumblebee doesn’t detect the card which results in an error. You need to define the card BusID in /etc/bumblebee/xorg.conf.nvidia, just uncomment the line where it has “BusID” and set it to the actual device ID. You can get that using lspci. In my case, it was “PCI:01:00:0”.

Power Saving

I was able to get a great 8-10 hours of battery with low brightness. I am using TLP for managing power saving.


Install TLP:

# pacman -S tlp tlp-rdw

Enable TLP:

# systemctl enable tlp.service
# systemctl enable tlp-sleep.service
# systemctl mask systemd-rfkill.service
# systemctl mask systemd-rfkill.socket
# systemctl enable NetworkManager-dispatcher.service

And since TLP enables NetworkManager by default, there is no need to enable that. You want to set TLP default mode to the battery. Edit /etc/default/tlp to have these settings:

# Operation mode when no power supply can be detected: AC, BAT.

# Operation mode select: 0=depend on power source, 1=always use TLP_DEFAULT_MODE

Also since we are using Bumblebee with Nvidia you have to make sure that TLP doesn’t enable power management for the card which can break auto switching with Bumblebee. You should avoid using powertop --auto-tune since it enables power management resulting in breaking Bumblebee. Make sure you have these lines in /etc/default/tlp to exclude the Nvidia card from power management:

RUNTIME_PM_DRIVER_BLACKLIST="amdgpu nouveau nvidia radeon"

Again make sure that you have the correct bus id for your card.


In /etc/modprobe.d/audio_powersave.conf add to enable audio power saving:

options snd_hda_intel power_save=1


Since this laptop comes with Intel Wireless 8265, we can use iwlwifi power saving options. Add these options in /etc/modprobe.d/iwlwifi.conf:

options iwlwifi power_save=1 d0i3_disable=0 uapsd_disable=0
options iwldvm force_cam=0

Intel GPU

Power saving options for Intel GPU, just stick this line in /etc/modprobe.d/i915.conf.

options i915 enable_guc=3 enable_fbc=1

Suspend and Hibernate

Personally, I prefer hibernating my machine whenever I do not use it for a long time, that is why I use suspend-then-hibernate. Suspend to RAM works out of the box, but hibernate requires some work. First, make sure you have either a swap partition or swap file. I went with swap file just because it does not require partitioning. According to Redhat Recommended System Swap Space, 1.5 of system RAM is the recommended amount of swap for hibernation which is 24Gb in this case.

# fallocate -l 24G /swapfile
# chmod 600 /swapfile
# mkswap /swapfile
# swapon /swapfile

Now define that within /etc/fstab for auto mounting:

/swapfile none swap defaults 0 0

In order for hibernate to work, you have to define where the system should look for the resume image in your Linux partition. You can define that in the kernel parameter in your bootloader resume=UUID=ce6dd35a-08d5-4b49-a46c-eff1de8937ce. Here I am using partition UUID, you can get that with sudo blkid. Since I am using a swap file, I also have to define a resume_offset=645120 which is the location of the swap file in the partition. You can get that using sudo filefrag -v /swapfile. Finally, add resume hook after udev and i915 module in /etc/mkinitcpio.conf. Regenerate initramfs sudo mkinitcpio -P.


  • Add pcie_aspm=force kernel parameter to enable ASPM (Active State Power Management).
  • Disable watchdog, add blacklist iTCO_wdt to /etc/modprobe.d/nowatchdog.conf.
  • Take a look at Improving Performance and Power Management.
  • Regenerate initramfs sudo mkinitcpio -P.
  • Regenerate grub.cfg sudo grub-mkconfig -o /boot/grub/grub.cfg.
  • Install Plymouth.
  • Enable auto-brightness aurman -S iio-sensor-proxy.


  • Config files used in this post etc.zip.

UPDATE 1 - fix sound

You can fix the sound issue with hdajackretask which is part of alsa-tools package then follow this picture and click on “Install boot override”:


You might need to set “connectivity” to “internal” to get it working. Finally, recreate your initramfs sudo mkinitcpio -P and reboot.


  • Missing hotkeys micmute, wlan, and pc manager now work using this driver. It will be part of linux 4.21 along with the speakers fix and micmute LED.
  • Some people reported slow network connection with the above settings. To fix that, drop uapsd_disable=0 from /etc/modprobe.d/iwlwifi.conf.
  • Also if you were using full disk encryption, don’t forget to add the speakers fix firmware files to /etc/mkiniticpio.conf like this: FILES=(/usr/lib/firmware/hda-jack-retask.fw).

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Suspend then hibernate in systemd 239

18 Jul 2018 0 Comments

In systemd 239, they have added a new service that handles suspending then hibernating after a given amount of time. This is easier than using external scripts since it comes built-in with this version of systemd. You can check systemd version with systemctl --version.

First, you have to define the delay time before the system wakes up and go into hibernation and that should be defined in /etc/systemd/sleep.conf


Here, what we care about is the last line HibernateDelaySec where you can define delayed time. As you see, I have it set to 15 minutes after suspending.

Lastly, we need to override the default suspend to execute suspend-then-hibernate instead of regular suspend:

# ln -s /usr/lib/systemd/system/systemd-suspend-then-hibernate.service /etc/systemd/system/systemd-suspend.service

This will make systemd executes suspend-then-hibernate instead of suspend every time suspend is invoked.




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Minesweeper using HTML5

13 May 2018 0 Comments

Obviously, everyone was born before the year 2000 knows the famous classic game ‘Minesweeper’. To me, I knew this game when I was little at the time where Windows XP was ruling everywhere. It is funny because at that time I did not know exactly how the game is played. That time the game was some kind of a luck game to me where you try to eliminate all the squares except the ones with mines until you either win or lose :laughing:.

Until recently, a friend pointed out that they saw a video of a guy who made a fully perfect AI to solve the game. I liked the idea so I decided to make one. I started by learning how the game works and it turned out to be very simple. There is a certain number of mines in the game and the player has to discover where these mines are to win the game. Every square has a weight that shows how many mines they are within the surrounding 8 squares of that particular square. If the weight was zero the game will reveal all the surrounding squares except the ones with the mines, otherwise, it will reveal the square itself. Although things did not go very well with the idea, I ended up making the game only.

How does it work?

With the help of HTML5 canvas element, you can draw geometric objects. We can achieve this dynamically using JavaScript. First, we create a canvas element in the page:

<canvas id="example" width="500" height="500">Any text here will get displayed if the browser does not support HTML5 canvas</canvas>

Then we use JavaScript to create objects and control their properties:

var canvas = document.getElementById("example");
var context = canvas.getContext("2d");
context.fillStyle = 'red';
context.fillRect(0, 0, 10, 10);

This will create a square with side equals to 10 and a position of (0, 0). Easy and simple.


Coming from an Object-Oriented Programming mentality, I wanted the ability to create classes just because I am used to it this way :smiley:. I was surprised when I knew that you can mimic creating classes in JavaScript .

I started by questioning what attributes each square has? And I came up with these: isMine, isFlagged, isDown, x, y, and weight. isMine tells if a square is a mine. isFlagged is when a square is being flagged or marked. isDown if a square is revealed. x and y hold the location in the game. weight is a number greater than zero where it holds how many mines within its surrounding squares. With these attributes I came with this JS class:

class square {
    constructor(x, y) {
        this.x = x;
        this.y = y;
        this.isDown = false;
        this.isMine = false;
        this.isDown = false;
        this.weight = 0;
    get x() { return this._x; }
    set x(value) { this._x = value; }
    get y() { return this._y; }
    set y(value) { this._y = value; }
    get weight() { return this._weight; }
    set weight(value) { this._weight = value; }
    get isDown() { return this._isDown; }
    set isDown(value) {
        this._isDown = value;
        if (this.isMine) {
            end = true;
    get isMine() { return this._isMine; }
    set isMine(value) { this._isMine = value; }
    get isFlagged() { return this._isFlagged; }
    set isFlagged(value) {
        this._isFlagged = value;
        if (value)
            numberofmines = (numberofmines <= 0) ? 0: numberofmines - 1;

The game does not have a loop, it contains two main functions. The first one is called to initialize the game environment like setting mouse event handler. Here is where all the magic happens, whenever the user clicks the first click the timer starts and it passes the click to the game. If it was inside the game frame where the squares are located it will register a click for that square. Otherwise, it will start a new game. Which is the second function, the previous function is only called once. This one is called to clear all the previous data in the game and create a start a new game. Obviously, this is done with the help of other functions to make it a little more organized.

Source code

The source code is available at JSMinesweeper or you can try it out here .

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