GNOME Bugzilla – Bug 338606
"Failed to start X" screen on tty2
Last modified: 2006-05-08 18:01:56 UTC
This bug has been opened on https://launchpad.net/distros/ubuntu/+source/gdm/+bug/29236 "The "Failed to start X" screen appears on tty2, which is OK by itself. But when the boot process finishes init will launch a getty on top of the "Failed to start X" screen. There are interesting side effects for this, if the user logs in the session works just fine until the user presses tab. At that point the gdm dialog will take precedence and hijacks the tty. Long story short, it might be good to launch the dialog to some other tty, the initial idea (AFAIK) was to launch the dialog in last+1 tty, but since gdm startup was moved up in the boot up, tty2 is not occupied at the time of the error itself. This has been checked with Dapper (upgraded from Breezy) ... > by default gdm uses tty7, you are saying that when you do ctrl-alt-F2 you get the gdm screen? ... Maybe i wasn't too clear about the problem: - Ubuntu boots - gdm fails to start and displays the error dialog - getty is launched on top of the error dialog Now, dialog takes some keypresses while others go to getty. The problem is that the dialog and getty get started on the same tty." Should XKeepsCrashing dialog be on tty7 too?
That happens only on boot. Restarting gdm from the command line then uses tty7 correctly. Any pointer on how to figure what is happening?
How would you suggest we fix this problem? Not use tty + 1 for messages that indicate GDM was having a failure starting up? Perhaps rip out the dialogs completely and just print messages to stderr? I'd accept a patch to fix this.
Sebastien, this sounds like a hard bug to look into. Why don't you turn on debug in GDM and see what gdm messages get sent to syslog. Attach the output to this bug report and I'll look at it too. Perhaps we can figure out what is going on. Also it would help me understand better if you explained more about how the system is configured. Could you explain in more detail about the init sequence that leads to the problem. Why does it fail and why does getty and GDM end up running on the same display? If this is causing problems for you, perhaps it would make sense to rip out the GDM code that pops up error dialogs when fatal errors happen. All these error messages basically say "can not run GDM for xyz reason" so it would probably be just fine to send such messages as normal console output. The number of users who are able to start X but fail to start GDM so the pop-up can be displayed in the first place is probably very small.
Sorry for the slow reply, I've a lot to do with the next Ubuntu version at the moment and sort of lag on bugs which has not to fix for that one. I'll try to get debug logs soon, but I think there was nothing really specific about the issue when I tried. What do you mean about the init sequence? I tried to "break" xorg by using a wrong driver name to xorg.conf so xorg doesn't start correctly. On boot gdm tries to start and then the ncurse fallback dialog is displayed on tty2 then some seconds later the getty prompt is displayed on it too. If I log to the system and restart gdm then the ncurse dialog is displayed on tty7 correctly, so it must be a race somewhere. Where is the gdm logic than determines what tty to use? You speak about users that are able to start X but not gdm to get the dialog, do we speak about the same dialog? The case pointed is gdm not starting correctly by xorg doesn't start correctly on the user installation
Reading back over my comments, I think I am a bit confused about the problem. You say that GDM fails to start the X server, but then you talk about the user logging into a session. Is this session on a different tty? Does the conflict happen on this other tty? At first I was thinking that the problem may be related to how GDM pops up dialog boxes to inform the user of various problems (calls to gdm_error_box), but if the Xserver isn't starting then its probably not popping up dialogs. It would be helpful if I had a better understanding of how GDM is messing up the tty's.
The issue seems to be fixed now, maybe due to a gdm update since 2.14.0 or to some Ubuntu change. Still describing what was happening before: - modify xorg.conf to use a wrong driver name by example - restart - xorg fails to start, gdm uses /etc/gdm/XKeepsCrashing - the ncurse box "Failed to start the X server (your graphical interface). It is likely that it is not set up correctly. Would you like to view the X server output to diagnose the problem?" is displayed on tty2 - wait a few seconds, the getty prompt is displayed on tty2, you can still read the dialog but "enter" doesn't do anything so it's not possible to display the xorg log from it Now the dialog is displayed on tty7 correctly. Closing the bug for now, I'll reopen with debug details if that happens again