tigervncserver crashes unless started with sudo

Question

I've installed the following pkgs:

ii  tigervnc-common                          1.10.1+dfsg-1                        amd64        Virtual network computing; Common software needed >
ii  tigervnc-standalone-server               1.10.1+dfsg-1                        amd64        Standalone virtual network computing server
ii  tigervnc-viewer                          1.10.1+dfsg-1                        amd64        Virtual network computing client for X
ii  tigervnc-xorg-extension                  1.10.1+dfsg-1                        amd64        Virtual network computing X server extension

I've run vncserver and configured a passwd and added no additional configurations.

(This is with an already working VNC session) Command without sudo:

root@kali:~# vncserver -localhost

New 'kali.'"'':2 (root)' desktop at :2 on machine kali.'"''

Starting applications specified in /etc/X11/Xvnc-session
Log file is /root/.vnc/kali.'"'':2.log

Use xtigervncviewer -SecurityTypes VncAuth -passwd /root/.vnc/passwd :2 to connect to the VNC server.


vncserver: Failed command '/etc/X11/Xvnc-session': 256!

=================== tail -15 /root/.vnc/kali.'"'':2.log ===================

Xvnc TigerVNC 1.10.0 - built Dec 30 2019 14:38:21
Copyright (C) 1999-2019 TigerVNC Team and many others (see README.rst)
See https://www.tigervnc.org for information on TigerVNC.
Underlying X server release 12006000, The X.Org Foundation


Sun Jan 12 18:52:25 2020
 vncext:      VNC extension running!
 vncext:      Listening for VNC connections on local interface(s), port 5902
 vncext:      created VNC server for screen 0
X connection to :2 broken (explicit kill or server shutdown).
 ComparingUpdateTracker: 0 pixels in / 0 pixels out
 ComparingUpdateTracker: (1:-nan ratio)
Killing Xtigervnc process ID 4108... which seems to be deadlocked. Using SIGKILL!

===========================================================================

Starting applications specified in /etc/X11/Xvnc-session has failed.
Maybe try something simple first, e.g.,
        tigervncserver -xstartup /usr/bin/xterm

When running with sudo and this works:

root@kali:~# sudo vncserver -localhost

New 'kali.'"'':2 (root)' desktop at :2 on machine kali.'"''

Starting applications specified in /etc/X11/Xvnc-session
Log file is /root/.vnc/kali.'"'':2.log

Use xtigervncviewer -SecurityTypes VncAuth -passwd /root/.vnc/passwd :2 to connect to the VNC server.

I'm root for both - so I'm looking to understand why sudo makes the difference

Answer 1

create executable file ~/.vnc/xstartup with the next content:

#!/bin/bash

PATH=/usr/bin:/usr/sbin
unset SESSION_MANAGER
unset DBUS_SESSION_BUS_ADDRESS
exec startxfce4 &

for the exec value check your desktop session with:

ls /usr/share/xsessions/

there you'll find .desktop files like:

cinnamon2d.desktop  cinnamon.desktop  gnome.desktop  gnome-xorg.desktop  
kodi.desktop

Open the file with the desktop environment you are interested in for your vnc session and check Exec variable there, for me it was cinnamon-session-cinnamon. So my ~/.vnc/xstartup looked like this:

#!/bin/bash

PATH=/usr/bin:/usr/sbin
unset SESSION_MANAGER
unset DBUS_SESSION_BUS_ADDRESS
exec cinnamon-session-cinnamon &

after this vncserver should start without any sudo requirements, at least, it did in my case. I guess the absence of the executable prevents vncserver from starting, but with sudo privileges it manages to start with default settings pulled from some files accessible for sudoers only.