What "Linux Operating System" do you use? (INCOMPLETE)

This post is to help you learn the basics of everything so you can see the full picture. If you have no idea what you're doing or if you're new to Linux, this post is for you. There are a billion different misconceptions, misunderstandings, and incorrect interpretations of concepts related to Linux, and in this post, we'll debunk them. I'm disappointed by the fact that nobody has written something like this before. There are plenty of YouTubers and content creators who post multiple videos a week, but none of them talk about this stuff. Absolutely pathetic! This guide will assume you're a Windows user. If you're a macOS user, you shouldn't have made it to my blog.

Note that I'll only be touching the surface of everything with very brief descriptions to keep things simple. The goal here is to help you see the full picture, not to master everything.

At the very low level, you have your hardware.

Linux Kernel

An operating system is not just one software. They consist of multiple major components. At the core is the kernel. This is what directly communicates with your hardware and exposes them through something called system calls (commonly referred to as "syscalls"). Every time a program needs to read a file, allocate memory, or send network data, it's the kernel that actually does it on behalf of that program.

Your "Windows 11 Operating System" uses Microsoft's proprietary Windows NT kernel, which you cannot legally or technically modify. In "Linux" systems, the kernel is Linux, created by Linus Torvalds. This is an open source project (licensed under GPLv2), meaning you can inspect its code, patch it, recompile it, and even redistribute own version.

On top of that, the kernel is what handles process scheduling, memory management, file systems, networking and all the other low level operating system related functions.

Device Drivers

Just above the kernel sits device drivers. These are small programs that tell the kernel how to talk to your specific hardware, like graphic cards, wifi adapaters and what not. In Linux, many drivers are built directly into the kernel or distributed as loadable kernel modules (LKMs) that can be dynamically added or removed (sometimes at runtime, without requiring restarts).

Graphics Drivers

One commonly talked about topic related to drivers in Linux is the graphics drivers for NVIDIA and AMD GPUs. If your GPU is AMD, the built-in drivers should have you covered.

Back in the day, AMD's Linux driver support wasn't always great. Years ago, AMD provided a closed-source driver called fglrx, which was often buggy and hard to maintain. Eventually, AMD realized that open collaboration with the Linux community was the best way to go. Therefore, they open-sourced large parts of their driver stack, and today the AMDGPU driver (maintained directly in the Linux kernel) and Mesa's open-source 3D stack deliver fantastic performance. As a result of this, if you own an AMD GPU, most modern distributions should support it out of the box without you having to install anything. It will just work!

If you have an NVIDIA GPU, your life gets a little complicated. You have two options:

1. The proprietary NVIDIA driver provided by NVIDIA themselves.
2. The Nouveau open-source driver, maintained by the Linux community.

If you just want to get on with life, you should consider using the proprietary driver over the open-source one. If you have ethical or freedom-related reasons, use the open-source driver. But if you're new to Linux and you want to use your hardware to its fullest potential, use the proprietary driver (like I do). While the latest versions of Nouveau and the proprietary driver might seem similar, the proprietary driver still tends to perform better and gives you access to all the advanced features of your GPU like CUDA, NVENC and full 3D acceleration.

NVIDIA has refused to fully open-source their driver stack multiple times, and this has long been a pain in the pass in the Linux community. The situation between NVIDIA and Linux has been so frustrating that Linus Torvalds himself once famously said, "Fuck you, NVIDIA". This video can be found here.

Wi-Fi Adapters

Another commonly talked about area is WiFi adapters. Most of them should work out of the box with the generic drivers included in the Linux kernel. Modern distros ship with a wide range of wireless drivers pre installed, so in many cases your Wi-Fi will just work out of the box.

If it doesn't, your next step is to check whether there's a package available for your adapter (we'll talk more about packages later). Many vendors and community maintainers publish driver packages that can be installed directly using your distro's package manager. They are usually named like broadcom-wl or rtl8821ce-dkms and so on.

If you can't find an official package, try searching online (especially on GitHub) to see if someone from the community has written or ported a driver for your chipset. If you find one, you can usually compile it from source and pray for it to work.

If you've tried all that and still can't get it to work, just give up at this point. Buy a new WiFi adapter that supports linux out the box to use

Init System

In the boot process of a linux system, once the kernel loads, a special userspace program called the "init system" starts. The kernel launches this with a PID (Process ID) of a 1. This acts like the root of all other processes. An init system is responsible for orchestrating the boot process. It starts all the other system services, handles shutdown and reboot sequences, and managed all the system services.

In linux systems, there are multiple init systems. At the very beginning, everything used the "SysV Init" system - short of System V Init. This was built to function like Unix System V. This uses 0-6 different run levels to define boot states and to make things simple, it is script based. All the init scripts are stored inside /etc/init.d/. Here, all the services launch sequencially (via those scripts) - therefore, resulting in a slower startup times. This init system is simple and easy to use but it lacks a lot of modern features like parallel startup of processes and the ability to monitor services.

Around 2006, Canonical released Upstart - a modern alternative to SysV. This performed faster comparatively and was event based. This gave the ability to perform certain things when an event was triggered - such as "when a device appears".

In late 2014, systemd was released. This is not just a basic init system, it is a complete system manager with modern highly sophisticated features. It introduced features like parallel startup of processes, service supervision (auto restart and service dependency ordering/management), a unified centralized logging system, a consistent configuration file format, timers and socket activation. Canonical discontinued upstart and adopted systemd for their linux distribution named Ubuntu. Most modern linux distributions use systemd as their init system.

Systemd works with service files, called units (basically configuration files). They define how a component behaves. By convention, each unit file is given a suffix to suggest the component type. Let's take a look at some of those.

• .service: These are used to contain information about individual services. They are also called daemons.
• .timer: These are used to perform shceduled jobs.
• .mount: These are used for file system mounts.
• .target: This is basically a group of services to start. An example is graphics.target, which starts all the graphics related services.

A simple .service unit file can be found below. As you can see below, using things like After=, you can handle dependencies easily. Here, the After=network.target will ensure that this service will start only after network.target component has been started. A list of all these directives can be found here in the official documentation.

[Unit]
Description=MyApp Service
After=network.target

[Service]
ExecStart=/apps/myapp/executable
WorkingDirectory=/apps/myapp
Restart=always
User=serviceuser
Group=servicegroup

[Install]
WantedBy=multi-user.target

To communicate with systemd, you should use the systemctl command line utility. This blog post covers the basic usage of services with systemd along with the basic usage of the systemctl command.