There is a major issue with Ubuntu partly due to BulletproofX and the X window system, which requires the presence of a monitor for X window to start. If the monitor is switched off, or is not connected, then Ubuntu / X would not be able to detect it and thus would go into “low graphics mode”. So, basically your GDM would not start.
There are two scenarios in which the monitor is not connected / switched off
- You wish to save energy and thus switch off the monitor, and then remotely reboot the machine
- You have Ubuntu running as a Server and thus no dedicated monitor is connected to it and you remotely reboot the machine. Specially, if you have automatic login enabled along with Remote Desktop (vino/vnc) enabled, and rely on Network Manager to start your session (through Wifi perhaps). In this case, Ubuntu would go into low graphics mode, and your network manager would not be able to assign you an IP, and you have lost complete remote access to the machine. Isn’t it pathetic?
I am still not aware on how to take care of the first part, that is, monitor switched off intentionally by you.
However, if you are running Ubuntu as a server and have/need a GUI, then the solution is here. Thanks to nikgare / http://ubuntuforums.org/showpost.php?p=7681232&postcount=8 for the pointer.
- Modify
/etc/X11/xorg.confand remove all content and add the following
Section "Device"
Identifier "Configured Video Device"
Driver "vesa"
EndSectionSection "Monitor"
Identifier "Generic Monitor"
HorizSync 58-62
VertRefresh 75-117
EndSectionSection "Screen"
Identifier "Default Screen"
Device "Configured Video Device"
Monitor "Generic Monitor"
DefaultDepth 24
SubSection "Display"
Depth 24
Modes "1024x768"
EndSubSection
EndSection
- You also may want to disable Bulletproof-X by modify /etc/gdm/gdm.conf and commenting out the line
#FailsafeXServer=/etc/gdm/failsafeXServer
Now reboot, and X would start without monitor plugged in.
Vivek's blog 
Thank you so much, that was really helpful for me! 🙂
YOU ARE MY HERO!!!
IT WORKS! Also on gentoo 😉
the only true guide.
thank U Vivek Kapoor, u save my day
That was exactly my problem.
Thank you very much.
Configurazione di un server x11vnc « Linux StickIt
It does not work on Ubuntu 11.10. I am running amd 64 version. Any other suggestions?
It doesn’t work on debian squeeze with kde 3.5…
This is quite retarded, logon actually works if you leave vga cable plugged in without monitor : ))
some VGA cables have monitor ident pins 4, 11 shorted to ground, one of mine does, another does not, which identifies any monitor to the PC as colour+1024/768 capable. May not work on newer machines that look for a serial ident.
It magically works on my machine (Ubuntu 10.10) XD, thank you!
I’ll give it a go tonight.. im running linux mint xfce and I’ve been trying to manage the thing via teamviewer. No success so far.. hopefully this will turn things around.
I am really not sure it’d work now as that was for a quite an old version of Ubuntu. Update us if it works now as well!