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learner
Asked: 2014-09-20 23:09:49 +0800 CST

What is a desktop environment, session and shell?

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This is how all happened. I was trying to search good screen recorder and found on some website that recordMyDesktop will work well under GNOME *Shell. So I tried searching in google "how to find whether I'm using gnome shell". The first link directed me to official gnome wesite there it showed a message as below. enter image description here So I thought it is something to do with desktop environment and continue browsing as below.

In this question I tried first answer to find my desktop environment, but the command DESKTOP_SESSION gave me "command not found". So I tried 5th answer by Nadiw. The command and output are as below.

ls /usr/bin/*session
/usr/bin/ck-launch-session  /usr/bin/gnome-session

So it is confirmed I'm using GNOME but it is not showing as desktop environment instead its showing "session", by which I got confused.

Hence I tried third answer by Luis Alvarado from this post. The command and output are as below

echo $XDG_CURRENT_DESKTOP
Unity

Now I found this totally irrelevant. My questions are

  1. If the desktop environment is Unity how can it use a session of GNOME and GNOME shell.

  2. How GNOME shell is different from bourne shell, t shell and others

  3. Or if one of the outputs I'm getting is wrong? Then how to find which DE i'm using? And which is the default DE for Ubuntu 14.04.

  4. On which of these factors I should depend while downloading a software? Whether it is Desktop Environment or session or shell?

14.04

2 Answers

  1. Best Answer

    DESKTOP_SESSION is not a command, it's a variable. You can do echo $DESKTOP_SESSION to see what the value is, just like with XDG_CURRENT_DESKTOP:

    $ echo $DESKTOP_SESSION 
gnome
$ echo $XDG_DESKTOP_SESSION

$ echo $XDG_CURRENT_DESKTOP
GNOME

    (I'm using GNOME Shell. Yes, I did not get any output for XDG_DESKTOP_SESSION. This is a known bug.)

    This output is not irrelevant:

    $ echo $XDG_CURRENT_DESKTOP
Unity

    It is the most relevant bit of information you have, that you are running the Unity shell.

    1. To install Gnome Shell:

      sudo apt-get install gnome-shell

      See the third of the reference links for screenshots for selecting Gnome Shell.

    2. The interface, the part that you interact with, is called a shell. The Bourne shell and other classic shells are command line shells. Gnome Shell, Unity, etc. are graphical shells.
    3. The default Desktop Environment for Ubuntu is GNOME 3, with the Unity shell and other modifications. Because the base is GNOME, you'll see some output which is true for GNOME Shell as well, for the various tests.
    4. Usually, none. The answer to this is very complicated and application-dependent. Have a look at the fifth linked question.

    As for the browser error, if it persists after you start using Gnome Shell, see the FAQ.

    Also see:

    1. What is the relationship between Unity, Gnome, Gnome 3, Compiz, Metacity, and LightDM?
    2. What kinds of desktop environments and shells are available?
    3. How do I install and use the latest version of GNOME?
    4. What is the default desktop environment for Ubuntu 13.10?
    5. When installing packages (particularly those with graphical UIs) how do you determine which is fitting for your distribution?
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  2. To answer your question number 2, a shell is command interpret. You communicate with OS through shell. In GNOME and Unity you do it graphically, by clicking on stuff, and in Bourne shell - by text commands entered into terminal

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