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Hi folks. I guess this might be a fairly basic question, but as I am still a bit confused about some of the basics, I thought I would ask some ...
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  1. #1
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    Terminal, CLI, console, shell, desktops sessions etc....


    Hi folks. I guess this might be a fairly basic question, but as I am still a bit confused about some of the basics, I thought I would ask some nice people as googling is coming up with answers, but confusing me further!

    My problem: I have installed openSuse 11.0, and am very pleased with it, it is far better than other (failed) attempts I have made to emigrate to linuxland. I would like to follow a step by step course in linux. I have found a couple of these course on the interweb, but I think I should be starting from runlevel 3. Now; is this called shell, CLI, or console?
    I know that if I open a terminal from KDE or gnome, the interface and 90% of commands are the same but, switching user, su, root and extra terminals are different, certainly alt+n commands are different, adding users seems to be different as far as I can see as well. Working as a different users for instance is giving me a headache, working through a course yesterday I found I was still logged on in a number of places, but I do not know how to log off!
    Unfortunately, the courses I have are natch, on the web. Can I have a full KDE session going as well as a session as another user in runlevel 3, and switch between the two? I would like to refer to the course, switch to the other user, try the examples, and switch back again to check if I go wrong, move on to next lesson etc. If this is not possible is there a way to display html from runlevel 3? Or if I cut the entire courses to some kind of document, can I show it formatted from there? I hope you can understand my daft questions, any pointers or links to resources explaining in noob terms the differences between the various concepts in the title, I would be grateful!

  2. #2
    Linux Engineer GNU-Fan's Avatar
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    Hello,

    "runlevel 3" in Suse just means that all basic system programs (called services) are running and that the system is set up to deal with multiple users simultaneously. One service that is not started in this runlevel is the graphical interface.

    "runlevel 5" in Suse means "runlevel 3" and some more services (graphics) are running. So 3 is a subset of 5 here.

    Therefore you will not need to bring the system down to level 3 in order to learn something yet.

    A shell is a computer program that accepts user commands and does the according action. One of such actions would be to start another program. (The shell cares about loading it into memory from the harddrive and tells the kernel to execute it).
    A shell can be graphic, like the KDE or GNOME desktop. And there are text shells like BASH that accept typed commands. The latter can also be called "Command Line Interface", or CLI.

    "Konsole" is the name of a program from KDE which displays text in a window within the graphical user interface. When this program is started, a CLI shell is started along with it and "connected" to this window. So you can type text into the window and this text is interpreted and obeyed by a shell.

    "Console" is a synonym for "text based user interface". The concept can be understood from the application's point of view. If a program wants to give out a text message, it just says to the system "write the line 'hello'" to _standard output_.
    The system then is responsible for printing it in the right place. You as an user see the difference between the "Konsole" application or a shell session in runlevel 3. For you it matters whether this is just another window on your desktop, a line printer or black and white fullscreen text.

    But for the application it is just the same: Something which text can be sent to.

    Hope this clears things a little.
    Debian GNU/Linux -- You know you want it.

  3. #3
    Linux Guru techieMoe's Avatar
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    Quote Originally Posted by WakouonSuSe View Post
    I have found a couple of these course on the interweb, but I think I should be starting from runlevel 3. Now; is this called shell, CLI, or console?
    Runlevel 3 on most versions of Linux (except Slackware) is a non-graphical command-line interface (CLI). You communicate by using a shell program (BASH usually). Sometimes this is also called a console, though that's a term that can be used for other things. So... the answer to your question is "all of the above." Hope that doesn't confuse you further.

    Working as a different users for instance is giving me a headache, working through a course yesterday I found I was still logged on in a number of places, but I do not know how to log off!
    Generally speaking, you can log off whatever your current user by typing logoff on the command line.

    Unfortunately, the courses I have are natch, on the web. Can I have a full KDE session going as well as a session as another user in runlevel 3, and switch between the two?
    Yes. I'm sure someone will correct me if I'm wrong, but I believe the keystrokes are CTRL+ALT+F1 to swap to a runlevel 3 terminal session, and CTRL+ALT+F7 to get back to your graphical X Session. You can have multiple terminal sessions with CTRL+ALT+F2/F3/F4/etc.

    If this is not possible is there a way to display html from runlevel 3?
    There are several text-mode web browsers out there. The most popular are lynx and links (no relation).
    Registered Linux user #270181
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  4. #4
    Linux Engineer GNU-Fan's Avatar
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    Quote Originally Posted by techieMoe View Post
    Yes. I'm sure someone will correct me if I'm wrong, but I believe the keystrokes are CTRL+ALT+F1 to swap to a runlevel 3 terminal session
    Actually you are not going into runlevel 3. Changing a runlevel implies logging out all interactive sessions. Instead the graphical system (the X11 server) is told to suspend the active graphical display (screen) and detach from all input (keyboard, mouse...).
    Then the xserver hands control over the screen and the input to the kernel, which gives you the fullscreen text session. (But in contrast to runlevel 3, the xserver keeps running in the background). On pressing (e.g.) CTRL+ALT+F7, the xserver claims back control of the graphics card.
    Debian GNU/Linux -- You know you want it.

  5. #5
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    Brilliant guys! I am not sure fully understood all of your answers, but these hints allow me to do exactly what I required. Respek innit!

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