On Thu, 14 Sep 2017 04:57:05 +0530
Arun Isaac <arunisaac@systemreboot.net> wrote:

> Thomas Danckaert writes:
> 
> > Hi Guix,
> >
> > since the change to networkmanager, I've been running into the 
> > following problem: when I connect to a wireless network using 
> > networkmanager, I can no longer start graphical applications 
> > (starting any program fails with “cannot open display :0.0” and 
> > similar messages).
> >
> > AFAIU, the cause is that networkmanager changes my hostname (after 
> > DHCP?), in my case to “new-host2” or something similar, and this 
> > seems to break the X session.  When I manually restore the hostname 
> > with “sudo hostname <original-hostname>”, the problem is solved.
> > Is there anyway to disable this behaviour for networkmanager?  
> 
> I have the exact same problem too. If somebody has a solution, I'd
> like to hear about it.

I created /etc/hostname and put the machines hostname in it, and I
don't think I've had the issue since. Perhaps try that?