Multiple X ( Desktop ) Sessions in Ubuntu

[Bob Jonkman]

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John wrote:
> ...a black blank screen that cannot be released, even with 
> ctrl+alt+backspace or ctrl+alt+delete.

Ctrl+Alt+Backspace hasn't been implemented in Ubuntu for about five
years.  Now the preferred way to restart X is with the Secure Access
Key, SysRq+Alt+K

There's a document on the various System Request keystrokes at
http://www.debian-administration.org/article/457/The_magic_sysreq_options_introduced

And the Internet is full of documents on how to restore
Ctrl+Alt+Backspace:
https://ixquick.com/do/metasearch.pl?query=ubuntu+ctrl-alt-backspace

- --Bob.


On 14-01-22 03:11 PM, John Moniz wrote:
> On 01/21/2014 10:25 PM, Aruna Hewapathirane wrote:
>> I was testing window managers and having a hard time comparing 
>> each due to constantly having to log-off and sign back in as 
>> another user with a different window manager and then something 
>> sweet happened. I came across a article and now I am flipping
>> back and forth between virtual terminals that have gnome-classic,
>> LXDE, Openbox and Awesome and it's amazing.
>> 
>> The article is here: 
>> http://www.doknowevil.net/2010/10/13/multiple-x-desktop-sessions-in-ubuntu/
>>
>>
>>
>>
>>
>> 
and for those of us who are lazy the content is right below,
>> seriously you should try this it blew me away :)
>> 
>> -------------------------------------------------------------------------------------------------------------------------------------------
>>
>>
>>
>>
>>
>> 
This post has a lot to do with graphics but there are no graphics.
>> It’s a walk-through explanation and and proof of concept of some
>>  very interesting features of Linux as a desktop operating
>> system.
>> 
>> If you aren’t familiar with X, than this webpage might confuse
>> you <http://www.x.org>, the X Window System 
>> <http://en.wikipedia.org/wiki/X_Window_System> is what draws the
>>  GUI (graphical user interface) for Ubuntu. On top of this, you
>> may have a Window Manager or Desktop Environment 
>> <http://xwinman.org/>, such as Gnome (Ubuntu default) or KDE 
>> (Kubuntu).
>> 
>> When you boot up Ubuntu, it creates a set of “virtual terminals”.
>>  These VTs are accessible via a key combination of clt+alt+f1-12.
>>  VT7 (ctrl+alt+f7) is the default and it handles X’s “screen 0″.
>> If you play around, with the key combination, you’ll notice you
>> drop into consoles with a login prompt (f1-6) or a blank screen 
>> (f8-f12, don’t worry if you see USB errors 
>> <https://bugs.launchpad.net/ubuntu/+source/linux/+bug/256767>).
>> 
>> These virtual terminals used to be handled by X which was slower
>>  and more prone to crash (citation needed) but since Ubuntu 8.04,
>>  this has been handled by “Kernel Mode” 
>> <https://wiki.ubuntu.com/X/KernelModeSetting>, where this 
>> management is handled by the kernel. You can switch to another 
>> virtual terminal and create another X session.
>> 
>> Typically in Linux, you could switch to another VT, login [as 
>> another user] and type $ *startx — :1* (special argument ‘|--|‘ 
>> marks the end of client arguments and the beginning of server 
>> options, :1 defines screen 1). This will work in Ubuntu but the 
>> part where I found it failing was switching between this newly 
>> created X session and back to my original :0 on VT7.
>> 
>> The way I found to do this in Ubuntu seems a bit 
>> counter-intuitive. Before I explain, you should create a new
>> user, if you don’t have another already. You can do this by going
>> to System > Administration > Users and Groups.
>> 
>> To create a second X session in Ubuntu, go to your logout menu 
>> (default top right) and select “switch user”, and login as
>> another user (you don’t want to create an error in the user
>> environment). When you login as another user, Ubuntu creates a
>> screen :1 on VT8. This means, you can change back to VT7 with
>> ctrl+alt+f7, then back to VT8 with ctrl+alt+f8. I /suspect/ this
>> is the reason VT8-12 show up as blank screens instead of login
>> terminals. Ubuntu seems to be leveraging the power of virtual
>> terminals for “user switches”.
>> 
>> I haven’t noticed much in performance loss doing this and the 
>> other big question is practicality. Why would you ever do this? 
>> Perhaps you are testing software and want isolated test cases or 
>> you want a dedicated user for games with a more streamlined
>> window manager and want to be able to flip back and forth.
>> 
>> -------------------------------------------------------------------------------------------------------------
>>
>
>>
>>
>>
>> 
> We use this method at home daily for one simple task. My wife and I
>  each have our own profile the first one to log on gets VT7, the
> next gets VT8. She switches to her profile using 'switch user', my 
> prederence is ctrl+alt+f7/8.
> 
> One annoyance that I have with a similar task in Ubuntu, and maybe
>  it's only on my machine, is that logging out of one user will
> result in a black blank screen that cannot be released, even with 
> ctrl+alt+backspace or ctrl+alt+delete. Whenever more than one user
> is logged on, we have to leave them on until it's time to shut
> down.
> 
> The above problem does not seem to occur on my mother-in-law's 
> machine using Ubuntu, or even in this one when using a different 
> distro.
> 
> John.
> 
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