Merge pull request #223 from network-charles/patch-1

What is Ubuntu Desktop made of?

Author: edibotopic

ubuntu-desktop/explanation/what-ubuntu-is-made-from.md

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+# What is Ubuntu Desktop made of?
+
+Ubuntu Desktop has millions of users today. As a new user, you might be curious to know what Ubuntu Desktop is made of.
+This guide explains the Ubuntu desktop environment, the types of applications it runs, how package managers work, and more.
+
+## Desktop environment
+
+The Ubuntu Desktop environment provides a Graphical User Interface (GUI) for interacting with Ubuntu.
+The GUI determines the visual appearance of the desktop and the user experience of interacting with its tools and applications.
+Ubuntu Desktop ships with the GNOME desktop environment by default. Other alternative desktop environments include:
+
+- KDE Plasma
+- XFCE
+- LXQt
+- MATE
+- Budgie
+
+Ubuntu Desktop comes in [different flavors](https://ubuntu.com/desktop/flavours), each with its own desktop environment.
+Flavours are unique and opinionated offerings of Ubuntu, with their own visual style and applications.
+For example, the Kubuntu flavor uses the KDE Plasma desktop environment by default, while Ubuntu Studio is specially designed for content creation.
+
+A desktop environment consists of different independent components, including:
+
+- **Windows manager**: This manages a window that pops up when you open a terminal or any application at all.
+- **User app**: These are default applications in the desktop environment.
+- **File manager**: This is a UI environment for interacting with files.
+
+Ubuntu Server is essentially Ubuntu Desktop without the desktop environment and some specialised applications installed for server management. Some of these applications include:
+
+- OpenSSH server
+- ping
+
+However, you can [install a GUI](https://documentation.ubuntu.com/aws/aws-how-to/instances/launch-ubuntu-desktop/#install-ubuntu-desktop-and-the-snap-store),
+on Ubuntu Server, and this is possible if your hardware supports graphics components.
+	
+## Applications
+
+These are comprised of system and user applications.
+
+- **System application**: The system applications interact with the operating system. Examples are the App Center and GNOME Terminal.
+- **User applications**: They are used to perform day-to-day activities and have permissions to the operating system restricted. Examples are Firefox and Calculator.
+
+## Package manager
+
+A package manager is used to manage your application lifecycle, including install, upgrade, update and remove. You can do this using a GUI applications or with the command line.
+
+- **The GUI**: Ubuntu Desktop comes pre-installed with an application store called the App Center. It provides a graphical interface that allows you to search for apps and install them.
+- **Command line**: Packages can be installed from the terminal using `apt` or `snap` commands:
+  - **apt (Advanced Package Tool)**: This is the default package manager on all Debian-based systems like Ubuntu.
+  - **snap**: Another built-in package management tool on Ubuntu, which includes all dependencies in a contained environment called a "snap".
+
+## Display server
+
+This ensures that GUI applications can communicate with graphics-related hardware and input devices, including the keyboard, mouse, and touchscreen.
+
+
+The display server consists of a communication protocol and a display server.
+
+- Protocol: Enables communication between the GUI applications and the display server. Examples are [X11](https://en.wikipedia.org/wiki/X_Window_System_core_protocol) and [Wayland](https://wayland.freedesktop.org/docs/html/).
+- Display server: Implements the protocol. Examples are [X.Org](https://www.x.org/wiki/) and [Weston](https://wayland.pages.freedesktop.org/weston/).
+
+Users of Ubuntu Desktop can currently choose between X11 and Wayland.
+
+## Services
+
+These are system applications running in the background. They often automatically start when Ubuntu Desktop boots. You can
+manage them using the `systemctl` command-line tool. These applications manage your Wi-Fi, Bluetooth, File System, and other settings.
+
+To list all your services, run:
+
+```shell
+systemctl list-units --all --type=service
+```
+
+## Shell
+
+A shell is a program that uses a non-graphical way to interact with the operating system. You can access it by launching
+a Terminal application.
+
+For example, you can run the following:
+
+- `pwd`: Shows your working directory. 
+- `ls`: Lists files in your current directory.
+See [The Linux command line for beginners](https://ubuntu.com/tutorials/command-line-for-beginners#1-overview) for more information about Linux commands.
+
+The terminal prompt ends with `$` for non-root users and `#` for root users.
+
+There are several types of shells available, including:
+
+- sh
+- bash
+- fish
+- zsh
+
+Tasks can be automated using shell scripts. To do that, define your task in a shell script that ends with a `.sh` file extension. Then, make the script executable and run it.
+For example, you can write a script that greets you with hello and displays the time.
+
+## Kernel
+
+This ensures that the Ubuntu operating system can communicate with the entire hardware. It's stored in a disk drive and loaded into RAM when Ubuntu Desktop boots.
+
+You can run Ubuntu Desktop in a virtual machine, which means both your host (such as Windows or macOS) and the Ubuntu Desktop guest run separate kernels.
+Check the path to where the Ubuntu Desktop kernel binary is stored by running:
+
+```bash
+ls /boot/vmlinuz-$(uname -r)
+```
+
+Examples of processes involving the kernel include:
+
+- When a display server is launched, its protocol communicates with the kernel, which then directs the request to the GUI-related hardware (GPU, frame buffer, etc.).
+- Storage and CPU resources can be allocated to a launched application running [outside the kernel](https://en.wikipedia.org/wiki/User_space_and_kernel_space).
+- An application can be loaded to run inside the kernel using [Extended Berkeley Packet Filter (eBPF)](https://documentation.ubuntu.com/server/explanation/intro-to/ebpf/).