Display Servers: X11 and Wayland
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Video Transcription
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>> Hey Cybrarians.
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>> Welcome back to the Linux+ course here at the Cybrary.
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>> I'm your instructor Rob Goelz.
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In today's lesson, we're going to
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be discussing Display Servers.
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Upon completion of today's lesson,
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you are going to be able to understand the importance of
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display servers in providing a GUI environment.
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We're also going to learn about the X11
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and Wayland display servers and then finally,
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we'll be able to explain how
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X11 and Wayland servers operate.
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Display server is just something that handles
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communication between the user interface,
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IEU typing on your keyboard,
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using your mouse and looking at the screen,
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and the back and the Kernel of the operating system.
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Communication is handled by a display server protocol,
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and that protocol can operate over a network.
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We'll see that later in this module when we
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talk about console redirection.
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Now display servers also
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run something called a compositor.
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in this program is what arranges
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the display elements within a window to create an image.
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When we drag a window around,
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what we actually are doing is working with
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the compositor to move that around on the screen.
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Now displays servers don't actually provide a desktop,
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that is generally done by a desktop environment,
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which will be covered in the next lesson.
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Now the X11 Display Server,
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we actually talked about this briefly in Module 13,
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but the X11 Display Server software
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was created by MIT in 1984.
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It's sometimes referred to as the X Windows Server,
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or X Windows System or just X. X11 is
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a legacy system that's still supported by the
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X.org foundation is open source.
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X11 is actually just X Windows System version
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11 or X11 for short.
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Now X11 does provide
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basic GUI operations such as resizing,
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clicking, and moving GUI programs on the screen.
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But the way that it actually does that is
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by calling out to a compositor.
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We can see that over on
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the right-hand side in the image here
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that's courtesy of Wayland free desktop. org website.
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What we see is the client's that are using
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the X server to get a GUI on the server.
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This server is calling for
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the compositor when you're trying to
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move stuff around on the screen
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to redraw the screen for you.
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Then the X Servers,
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really just the middleman between the client,
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that compositor and the backend with the kernel.
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KMS, evdev and the kernel itself.
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X11 includes drivers so
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that everything can interact with each other,
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so it has drivers for
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the system hardware such as the mouse,
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video card, keyboard monitor,
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all the stuff that you're going to need.
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Now X11 has configuration files
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to look at and they're stored in a
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couple of different places.
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The first place /etc/X11/xorg.conf, that's
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the default location and then you may also see in
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some cases that several configuration files may be
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stored in /etc/X11/xorg.conf.d,
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that's just a directory where a lot
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of configuration files are stored
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if they're broken out across
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many different configuration files.
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In general though, if you're just looking at
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the default xorg.conf file,
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it's going to have a lot of sections in it.
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We have a couple of them over
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here on the right-hand side.
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For example, we have the files section which shows
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the locations of all the files that X11 needs to run.
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There's also a section for input devices and the
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handles the input for things like mouse and keyboards.
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In fact, here we see that we have one input device,
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the keyboard, and another input
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device setting for the mouse.
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There's also a modes section of this file that
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handles display modes, resolutions,
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and refresh rates on monitors
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and the screen section that has
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configuration settings for the video card
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and the monitor as well.
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In general though, don't touch X11 config,
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it's tricky, it's really easy to mess up.
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It's generally just installed
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as part of a graphical desktop.
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Again, we'll talk about desktop environments
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in the next lesson,
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but if you do for any reason,
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have to modify it,
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use the x.org- configure command.
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It's going to detect all of
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the hardware and create a new configuration file,
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and that will be put into /root/ xorg.conf.new.
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The Wayland Display Server was created in 2009.
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It was generally just intended to replace
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X11 because it's designed to be simpler,
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more secure, and easier to develop and maintain then X11.
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It's, also more lightweight
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because it has newer kernel features
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than what there was previously
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available to the X11 environment.
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Today, Wayland is actually
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the default display server for Fedora,
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which is an RPM based distribution,
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and is also supported in GNOME.
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Wayland is actually an umbrella term.
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It's the name for the protocol,
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so it covers the display server compositor in
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the windows server as
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one overarching term for all of them.
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Now if you look at the Wayland layout here,
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what Wayland likes to say is that
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the compositor is the display server.
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The display server doesn't have to call out to
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a separate compositor to arrange windows elements.
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There's a name for the compositor
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in Wayland is called Weston,
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but it's just all part of the same thing.
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We can see that here on
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the right-hand side in the image we have,
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again, courtesy of Wayland.
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We have two clients that are
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talking to the Wayland compositor,
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which is also the display server,
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and that just talks between the clients
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and into the back-end to the KMS evdev and the kernel.
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There's no need to call out to compositor because it's
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all handled through the same thing.
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Now, Wayland's Compositor does provide a basic desktop.
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It's swappable, but that's just meant as
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a reference for developers to create their own.
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It's not meant to be a full fledged a
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development environment or desktop
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environment for anyone to use.
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Many desktop environments create
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their own compositor even if they use Wayland.
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For example, in CentOS,
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Wayland is just configured to be
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part of the GNOME Desktop Manager.
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With that, in this lesson,
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we covered the importance of display servers
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and providing a GUI environment,
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and then we talked about the X11 and
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Wayland display servers and how they operate.
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Thanks so much for being here and I look
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forward to seeing you in the next lesson.
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