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Consider an industrial computer (say "embedded system"),

  • equipped with a linux server OS (no desktop)
  • running just a SINGLE application process (a single non-root user)
  • attached to an high resolution screen
  • attached with a keyboard

The computer fully dedicated to a SINGLE application process/user,

  • running in background (to be defined) and started at boot
  • run some I/O logics
  • get some user inputs (keystrokes/digits) from the keyboard
  • has to display some text/images on a screen attached to the computer

BTW, for text display details see also the related question: display big texts (on a graphic mode?) without a desktop environment).

    linux server host (no desktop env)
    +-------------------------------------------+
    |                                           |
    |                                           +--------> Digital inputs
    |   +--------------+                        <--------- Digital outputs
    |   | graphic card |                        |
    +---+------+-------+--------------------^---+
               |                            |
               | HDMI / VGA                 | USB
+--------------v---------------+    +-------+--------+
| Please contact the operator. |    |                |
+------------------------------+    +----------------+
      screen (TTY console?)              keyboard

How can the (background) process print text (in text-terminal mode or in graphic mode) on the attached (dedicated) screen, and get keystrokes from the keyboard?

OUTPUT

For output, I presume that one solution is that the process prints output texts as images, directly writing on the framebuffer (by example using program fbi.

But how if I would use the screen as a stdout of the (background) process? In this case I guess I need to "uncouple" the root TTY from the attached screen (that's possible?), allowing the user process to get the full control of the screen. It make sense?

INPUT

How can I take keystrokes from the keyboard? Using the stdin? Reading the keyboard device directly?

BTW, I presume to access the computer for any (root) need, over SSH.

Any suggestion?

Giorgio Robino
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    Maybe you'd want to replace getty with the program you want to run (or something that relays the input to your program)? https://raymii.org/s/tutorials/Run_software_on_tty1_console_instead_of_login_getty.html – rudib Nov 22 '20 at 12:24
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    Or you use cat /dev/tty1 (but this will block whatever is running in it frim getting the input). https://stackoverflow.com/questions/31440833/how-to-redirect-input-from-another-tty – rudib Nov 22 '20 at 12:41
  • Your question is confusing, it contains contradictions: Headless (meaning no display), and a description of a display. Please edit to remove any jargon words, and just say what you want. – ctrl-alt-delor Nov 22 '20 at 13:45
  • Are you asking. How can I set up a system with a single graphical application, but no window-manager, start-button, task-bar, etc? – ctrl-alt-delor Nov 22 '20 at 13:46
  • @ctrl-alt-delor headless === linux server (no desktop). Where is the contradiction? Anyway I removed the term headless if confuses. – Giorgio Robino Nov 22 '20 at 15:00
  • "high resolution screen" the head. Maybe because it looks like a head and the computer part looks like shoulders (on a desktop configuration). Am I grokking you correctly? – ctrl-alt-delor Nov 22 '20 at 18:15
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    Does this help? https://doc.qt.io/archives/4.6/qt-embedded-running.html You can run a single app that's its own server process as well using embedded Qt ... – tink Nov 23 '20 at 01:32

1 Answers1

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If you are asking. How can I set up a system with a single graphical application, but no window-manager, start-button, task-bar, etc?

Then.

You just need to not run the desktop: Window manager, and panel. There are just other processes. The process that starts the X11 server, will also start these. You just need to change the configuration.

ctrl-alt-delor
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  • Yes, I'd avoid desktop, form some reasons. I don't want: windows manager multi users. No X11 server. No background related processes. What's your solution/proposal? Configuration of what? – Giorgio Robino Nov 22 '20 at 15:05
  • Is the app just text? if it is graphical, then you need an X11 server (or wayland, or ..) – ctrl-alt-delor Nov 22 '20 at 18:16