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I am trying to understand what is the use of Xorg. I got confused with lots of words like window manager display manager login manager etc.

After that i got some links in stackexchange Terminology reconciliation: Display manager vs. session manager, Windowing system vs. Window manager It also making me confused.

I tried to install arch linux with the help of wiki. I never installed xorg. And i got only a terminal with login user name and password. Then what is the use of Xorg, xinitrc window manager display manager etc.

Little I google I came to know like windows manager is responsible for position , windows border close button etc. Then my question is what order it execute? What is use of each of these things? Can I run a GUI application without these all things? What are the mandatory service required for GUI applications? Why I asked this question is dwm suckless utility, when we install we install only xorg.

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    Please tell me why this question is down voted – Vipin Jun 3 '19 at 5:21
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    Probably because you are asking about an explanation of the whole concept of graphical user interface (GUI) on Unix. – RalfFriedl Jun 3 '19 at 5:30
  • I don't want the whole concept i have only three question. What order it execute? what all element involved. What all optional? Left-out part i can find myself. For a kick start i need these 3 question answer – Vipin Jun 3 '19 at 6:03
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    Is this your first Gnu/Linux? If so then I recommend that you start with a distro that is simple to install. – ctrl-alt-delor Jun 3 '19 at 6:46
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    @ctrl-alt-delor this is not the first linux. I used ubuntu earlier. And it came as a package. Nothing i could able to understand more. From past 6 to 7 month shifted to arch Linux. And exploring this linux through there wiki. I came across with project suckless utilities. So gone through some steps. Just under it better i asked these three questions. – Vipin Jun 3 '19 at 6:58
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The display manager, as the name says, manages a "display" (or sometimes several), in the world of X that is a monitor/keyboard/mouse combination somewhere. Decades ago there were multiple such "displays" attached to a single machine; today it is rare to see more than one (and multi-seat gets handled a bit differently).

The display manager can start the X server for that display, will restart it if it fails, and also (usually) presents a login screen to the user. So in that sense it is a "login manager" (though I've never heard the term "login manager" used).

So the display manager is started first. xdm is one of the oldest display managers, both Gnome and KDE have their own display manager (gdm and kdm), and there are others like e.g. lightdm.

The X server is a program that allows X clients (application programs) to put content on a display. Clients talk to the server locally or (rarely today) over the network using the X protocol.

The X server is started by the display manager, but you can also start the X server manually (often with a program called startx) if you don't use a display manager.

There are no variations for the X server (simplifying a bit). However, modern distros increasingly use Wayland as an alternative to the X server.

A Window Manager (WM) is a special X client with privileges that allow it to control the windows of other applications to some degree. It will paint decorations (like title bars) around those windows, it will implement key bindings to manipulate windows, it will deal with requests to iconify, minimize, maximize, or otherwise change the size of the windows, etc.

There are many different window managers, which one to use depends on your taste. The window manager is usually started by the display manager when it executes (default or customized) scripts during the login of a specific user. So each user can have a different window manager.

On modern distros, you never have to deal with all of that yourself (unless you want to): You can just pick a Gnome or KDE desktop (or other variants), and everything will be installed and configured for you.

Or you can mix and match, and install those parts you want of you don't want to use any of the "big" desktops (for example, I use xdm and fvwm). But then you need to understand the parts a lot better.

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  • First Xorg: This is the canvas that everything is drawn on, plus the keyboard and mouse.
  • Then display manager: This is a login manager.
  • Then a window manager: This manages the windows, allows user to move, resize, etc.
  • Other desktop tools may also be run: panels (the strip at the top/bottom/side) etc.

The system is (see dictionary) everything.

I would recommend trying some experiments. Here is a suggested challenge (you will learn much doing it, and it should take 1→3 hours (tell be after how long it took)).

If you are logged in then you can skip the display manager, and bring up X11 (xorg), with just a terminal. From there you can launch other programs such as xeyes, and/or a window manager. You can then run some more programs, and exit the window manager, and start a different one.

step one (hover to see)

ctrl-alt-F2
export DISPLAY=:1
sudo xorg $DISPLAY -retro &
go back to ctrl-alt-F2 to start an xterm.

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  • Thank you so much for you answer. Just a clarification, It means i can start a display server. Then after i can install dwm. No need login manager and desktop environment etc? – Vipin Jun 3 '19 at 7:07
  • Yes display-manager (the login-manager) is a convenience: it logs you in, and starts everything. The desktop environment is what you can create manually. The practical minimum is X11 (xorg) and a window manager), the absolute minimum is X11(xorg). Start with the obsolete minimum (if you are doing it to learn). – ctrl-alt-delor Jun 3 '19 at 7:11
  • I will try this challenge – Vipin Jun 3 '19 at 7:11

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