> hostnamectl set-hostname fedora.local.home.ionic.de
>
> Then, I edited /etc/hosts and added:
>
> 192.168.122.128 fedora fedora.local.home.ionic.de
>
> This leads to exactly the problem you described.
>
>
> If I change "fedora" to resolve to 127.0.0.1 instead (with
> fedora.local.home.ionic.de staying on 192.168.122.128), I can connect via X2Go
> again.
>
> Can you confirm this?

Just making this one change to the /etc/hosts file didn't change anything. However when I used the hostnamectl command I was able to get the dialog box asking me to continue or terminate what had to be 15 sessions. After terminating them all I got the X2Go screen for about 3 seconds and then it quit with the following segfault:

Nov 10 13:58:11 sobolev /usr/bin/x2goruncommand[2728]: dbus wrapper available as /usr/bin/dbus-run-session

Nov 10 13:58:12 sobolev kernel: glxinfo[2769]: segfault at 0 ip 00007f31b6cc4627 sp 00007fffb61bc838 error 4 in libX11-xcb.so.1.0.0[7f31b6cc4000+1000]

Nov 10 13:58:12 sobolev systemd[1]: Started Process Core Dump (PID 2773/UID 0).

Nov 10 13:58:12 sobolev systemd-coredump[2774]: Process 2769 (glxinfo) of user 1000 dumped core.#012#012Stack trace of thread 2769:#012#0 0x00007f31b6cc4627 XGetXCBConnection (libX11-xcb.so.1)#012#1 0x00007f31b838eb46 __glXInitialize (libGLX_indirect.so.0)#012#2 0x00007f31b838a4a4 GetGLXPrivScreenConfig (libGLX_indirect.so.0)#012#3 0x00007f31b838b375 glXChooseVisual (libGLX_indirect.so.0)#012#4 0x000055f5cc3c2b6a main (glxinfo)#012#5 0x00007f31ba57b88a __libc_start_main (libc.so.6)#012#6 0x000055f5cc3c32fa _start (glxinfo)

Nov 10 13:58:13 sobolev abrt-server[2836]: Deleting problem directory ccpp-2017-11-10-13:58:12.853273-2769 (dup of ccpp-2017-11-10-13:54:22.364670-28375)

Nov 10 13:58:13 sobolev abrt-notification[2946]: Process 28375 (glxinfo) crashed in XGetXCBConnection()

Nov 10 13:58:13 sobolev kernel: mate-session[2731]: segfault at 0 ip 00007f3ffb453627 sp 00007ffeda962b68 error 4 in libX11-xcb.so.1.0.0[7f3ffb453000+1000]

Nov 10 13:58:13 sobolev systemd[1]: Started Process Core Dump (PID 2975/UID 0).

Nov 10 13:58:14 sobolev systemd-coredump[2976]: Process 2731 (mate-session) of user 1000 dumped core.#012#012Stack trace of thread 2731:#012#0 0x00007f3ffb453627 XGetXCBConnection (libX11-xcb.so.1)#012#1 0x00007f3ffc2b9b46 __glXInitialize (libGLX_indirect.so.0)#012#2 0x00007f3ffc2b54a4 GetGLXPrivScreenConfig (libGLX_indirect.so.0)#012#3 0x00007f3ffc2b5d11 glXQueryServerString (libGLX_indirect.so.0)#012#4 0x00007f40098b8939 epoxy_glx_version (libepoxy.so.0)#012#5 0x00007f400cbeb869 gdk_x11_screen_init_gl (libgdk-3.so.0)#012#6 0x00007f400cbebc3a _gdk_x11_screen_update_visuals_for_gl (libgdk-3.so.0)#012#7 0x00007f400cbf4965 _gdk_x11_screen_init_visuals (libgdk-3.so.0)#012#8 0x00007f400cbf1990 _gdk_x11_screen_new (libgdk-3.so.0)#012#9 0x00007f400cbe154d _gdk_x11_display_open (libgdk-3.so.0)#012#10 0x00007f400cbb5c13 gdk_display_manager_open_display (libgdk-3.so.0)#012#11 0x00007f400d0a4f50 gtk_init_with_args (libgtk-3.so.0)#012#12 0x000055e55977eace main (mate-session)#012#13 0x00007f400ac7588a __libc_start_main (libc.so.6)#012#14 0x000055e55977f66a _start (mate-session)

Nov 10 13:58:14 sobolev /usr/bin/x2gofeature[2987]: x2gofeature called with options: X2GO_RUN_EXTENSIONS

Nov 10 13:58:14 sobolev /usr/share/x2go/x2gofeature.d/x2goserver-extensions.features[2993]: x2goserver-extensions.features called with options: X2GO_RUN_EXTENSIONS

Nov 10 13:58:14 sobolev /usr/bin/x2goserver-run-extensions[3000]: x2goserver-run-extensions called with options: localguy-51-1510340283_stDMATE_dp32 post-runcommand

Nov 10 13:58:14 sobolev /usr/bin/x2gofeature[3021]: x2gofeature called with options: X2GO_DESKTOPSHARING

Nov 10 13:58:14 sobolev /usr/share/x2go/x2gofeature.d/x2goserver-extensions.features[3041]: x2goserver-extensions.features called with options: X2GO_DESKTOPSHARING

Nov 10 13:58:14 sobolev /usr/share/x2go/x2gofeature.d/x2goserver.features[3047]: x2goserver.features called with options: X2GO_DESKTOPSHARING

Nov 10 13:58:15 sobolev abrt-server[2995]: Deleting problem directory ccpp-2017-11-10-13:58:14.112723-2731 (dup of ccpp-2017-11-10-13:54:24.515378-28338)

Nov 10 13:58:15 sobolev /usr/share/x2go/x2gofeature.d/x2goserver-xsession.features[3054]: x2goserver-xsession.features called with options: X2GO_DESKTOPSHARING

Weirdly, this seems not to happen if the hostname is *not* set to a FQDN. I have

a machine that is working flawlessly with such a setup:

hostname: shortname
/etc/hosts: shortname or FQDN not set
dns: returning public IPv4 and IPv6 addresses for FQDN; shortname will be
extended to FQDN automatically (and hence also resolves to these public addresses)

In this scenario, connecting via X2Go works just fine, even though neither
address is 127.0.0.1.

Just to confirm the /etc/hosts file now looks like this:

127.0.0.1 localhost localhost.localdomain localhost4 localhost4.localdomain4

::1 localhost localhost.localdomain localhost6 localhost6.localdomain6

#150.108.64.57 sobolev.dsm.fordham.edu sobolev

150.108.64.57 sobolev.dsm.fordham.edu 127.0.0.1

150.108.64.65 mandelbrot.dsm.fordham.edu mandelbrot

150.108.64.52 dsm.dsm.fordham.edu dsm