SOLVED! Thanks for your help, as in many things, the problem is in the details:

aptitude shows what the problem is:

Unua:~# aptitude install x2goserver
The following NEW packages will be installed:
  libnx-xcomposite1{a} libnx-xdmcp6{a} libnx-xfixes3{a} libnx-xinerama1{a} libnx-xpm4{a} nxagent{ab} x2goagent{a} x2goserver x2goserver-extensions{a}
  x2goserver-xsession{a}
0 packages upgraded, 10 newly installed, 0 to remove and 2 not upgraded.
Need to get 2,182 kB of archives. After unpacking 7,347 kB will be used.
The following packages have unmet dependencies:
 nxagent : Depends: libnx-xdamage1 (< 2:3.5.0.32-0x2go1+git20160614.734+jessie.main.1.1) but 2:3.5.0.32-0x2go1+git20160614.734+wheezy.main.1 is installed.
           Depends: libnx-xrandr2 (< 2:3.5.0.32-0x2go1+git20160614.734+jessie.main.1.1) but 2:3.5.0.32-0x2go1+git20160614.734+wheezy.main.1 is installed.
           Depends: libnx-xtst6 (< 2:3.5.0.32-0x2go1+git20160614.734+jessie.main.1.1) but 2:3.5.0.32-0x2go1+git20160614.734+wheezy.main.1 is installed.
------------------
Now you will see that it says IS INSTALLED. Meaning: there are remants of old libs still hanging around from the wheezy install.
Now let's see what apt-get says:

The following packages have unmet dependencies:
 nxagent : Depends: libnx-xdamage1 (< 2:3.5.0.32-0x2go1+git20160614.734+jessie.main.1.1) but 2:3.5.0.32-0x2go1+git20160614.734+wheezy.main.1 is to be installed
           Depends: libnx-xrandr2 (< 2:3.5.0.32-0x2go1+git20160614.734+jessie.main.1.1) but 2:3.5.0.32-0x2go1+git20160614.734+wheezy.main.1 is to be installed
           Depends: libnx-xtst6 (< 2:3.5.0.32-0x2go1+git20160614.734+jessie.main.1.1) but 2:3.5.0.32-0x2go1+git20160614.734+wheezy.main.1 is to be installed

This is plain simple wrong. I checked and these libs are in fact installed, so I removed them and now I could install x2goserver without a problem.
apt-get is saying that they will be installed, but not that THEY ARE installed, kind of misleading.
I have had the experience in the past, that aptitude just does a little more, is a little more intelligent and can sometimes help you out of a pinch that apt-get left you in.

Thanks for the suggestion and help, the problem was solved really fast.

Markus

On Thu, Oct 6, 2016 at 11:12 PM, Robert Dinse <nanook@eskimo.com> wrote:

     Might also try Synaptic and try the Fix Broken option.  It has sorted
out dependencies that I haven't been able to before.

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   Knowledgeable human assistance, not telephone trees or script readers.
 See our web site: http://www.eskimo.com/ (206) 812-0051 or (800) 246-6874.

On Thu, 6 Oct 2016, Matt Weatherford wrote:

Date: Thu, 6 Oct 2016 23:07:09 -0700
From: Matt Weatherford <mbw@u.washington.edu>
To: Nigra Truo <nigratruo@gmail.com>
Cc: x2go-user@lists.x2go.org
Subject: Re: [X2Go-User] Cannot install X2goserver on Debian 8,
    stuck in dependency hell



Nigra,

this sounds like a really, really messy apt dependency problem.  Im not sure that this question is in scope for the x2golist,
as many of us use x2go server on Debian 8 Jessie without any issues

Can you back up your server config files (/etc, /var) and do a fresh install of debian 8 ?
That is probably going to be the safest thing to do for the long run.

That said, if you really want to try to untangle this huge ball of twine, you could try "apt-get install aptitude" and then use
"aptitude install x2goserver" to see if aptitude will tell you more information about the problem and the dependencies.

you can also "apt-get install apt-show-versions"  a tool I find helpful... then

apt-show-versions | grep x2go
apt-show-versions | grep nx

this might be interesting to look at & give you more info on where to start.

Matt





On 10/6/16 8:16 PM, Nigra Truo wrote:
Hi,


I just upgraded a server to Debian 8 and had X2goserver running on it before, but purged all the config and everything, because some things were not working properly, now I can't install it anymore, it refuses with these errors:

# apt-get install x2goserver
Reading package lists... Done
Building dependency tree... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
 x2goserver : Depends: x2goagent (>= 2:3.5.0.25-0~) but it is not going to be installed
E: Unable to correct problems, you have held broken packages.

-------------------------------------------------------
Trying to install that, it unravels an endless tale of dependency hell:
-------------------------------------------------------


Unua:~# apt-get install x2goserver x2goagent
Reading package lists... Done
Building dependency tree... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
 x2goagent : Depends: nxagent (>= 2:3.5.0.32-0x2go1+git20160614.734+jessie.main.1)
             Depends: nxagent (< 2:3.5.0.32-0x2go1+git20160614.734+jessie.main.1.1)
E: Unable to correct problems, you have held broken packages.
Unua:~# apt-get install x2goserver x2goagent nxagent
Reading package lists... Done
Building dependency tree... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
 nxagent : Depends: libnx-xdamage1 (< 2:3.5.0.32-0x2go1+git20160614.734+jessie.main.1.1) but 2:3.5.0.32-0x2go1+git20160614.734+wheezy.main.1 is to be installed
           Depends: libnx-xrandr2 (< 2:3.5.0.32-0x2go1+git20160614.734+jessie.main.1.1) but 2:3.5.0.32-0x2go1+git20160614.734+wheezy.main.1 is to be installed
           Depends: libnx-xtst6 (< 2:3.5.0.32-0x2go1+git20160614.734+jessie.main.1.1) but 2:3.5.0.32-0x2go1+git20160614.734+wheezy.main.1 is to be installed
E: Unable to correct problems, you have held broken packages.

--------------------------------------------------------------------
Here is my sources.list file: I don't understand why this is not working :-( Why is it still referring to wheezy? There is no mention anymore in sources.list file
-------------------------------------------------------
#deb http://www.debian-multimedia.org/ squeeze main non-free
deb http://www.deb-multimedia.org jessie main non-free


#Jessie official
deb http://httpredir.debian.org/debian jessie main contrib non-free
deb-src http://httpredir.debian.org/debian jessie main contrib non-free

deb http://httpredir.debian.org/debian jessie-updates main contrib non-free
deb-src http://httpredir.debian.org/debian jessie-updates main contrib non-free

deb http://security.debian.org/ jessie/updates main contrib non-free
deb-src http://security.debian.org/ jessie/updates main contrib non-free


# X2Go Repository (release builds)
deb http://packages.x2go.org/debian jessie main
# X2Go Repository (sources of release builds)
deb-src http://packages.x2go.org/debian jessie main



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