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Thread: Lightdm fails at startup

  1. #1
    Join Date
    Jan 2013
    Beans
    23

    Lightdm fails at startup

    Hi! I would need some help to understand what's happening better, please. I have a recurring problem. On startup, my computer boots, but when the time comes for the greeter screen to appear, the Ubuntu Studio image just disappears and the screen turns black. Then I have to use the following commands (after pressing ctrl+alt+f1) to be able to log in using the user graphical interface.

    Code:
    sudo service lightdm stop
    sudo service lightdm start
    Once I do that, I can access the greeter and log in normally. I tried to look at lightdm's logs from my normal session, but they looked normal, so I restarted and copied the logs in a different folder before restarting lightdm. Here is what the log looks like:

    Code:
    [+0.00s] DEBUG: Logging to /var/log/lightdm/lightdm.log
    [+0.00s] DEBUG: Starting Light Display Manager 1.4.0, UID=0 PID=1530
    [+0.00s] DEBUG: Loaded configuration from /etc/lightdm/lightdm.conf
    [+0.00s] DEBUG: Using D-Bus name org.freedesktop.DisplayManager
    [+0.00s] DEBUG: Registered seat module xlocal
    [+0.00s] DEBUG: Registered seat module xremote
    [+0.00s] DEBUG: Adding default seat
    [+0.00s] DEBUG: Starting seat
    [+0.00s] DEBUG: Starting new display for greeter
    [+0.00s] DEBUG: Starting local X display
    [+0.01s] DEBUG: Using VT 7
    [+0.01s] DEBUG: Activating VT 7
    [+0.01s] DEBUG: Logging to /var/log/lightdm/x-0.log
    [+0.01s] DEBUG: Writing X server authority to /var/run/lightdm/root/:0
    [+0.01s] DEBUG: Launching X Server
    [+0.01s] DEBUG: Launching process 1574: /usr/bin/X :0 -core -auth /var/run/lightdm/root/:0 -nolisten tcp vt7 -novtswitch
    [+0.01s] DEBUG: Waiting for ready signal from X server :0
    [+0.01s] DEBUG: Stopping Plymouth, no displays replace it
    [+0.41s] DEBUG: Process 1574 terminated with signal 6
    [+0.41s] DEBUG: X server stopped
    [+0.41s] DEBUG: Removing X server authority /var/run/lightdm/root/:0
    [+0.41s] DEBUG: Releasing VT 7
    [+0.41s] DEBUG: Display server stopped
    [+0.41s] DEBUG: Stopping display
    [+0.41s] DEBUG: Display stopped
    [+0.41s] DEBUG: Stopping X local seat, failed to start a display
    [+0.41s] DEBUG: Stopping seat
    [+0.41s] DEBUG: Seat stopped
    [+0.41s] DEBUG: Acquired bus name org.freedesktop.DisplayManager
    Does anybody have an idea of what's happening? I have bumblebee and CUDA installed.

  2. #2
    Join Date
    Jan 2013
    Beans
    23

    Re: Lightdm fails at startup

    Well, I'd really like to know what was wrong, but it's too late now. I wondered if reinstalling Xorg, lightdm and lightdm-gtk-greeter would fix the problem, and it did. What annoys me is that now I can no longer replicate the bug and won't know what was wrong. If anybody has an idea of what could potentially cause that, please tell me, even if this thread is technically solved.

  3. #3
    Join Date
    May 2010
    Location
    uk
    Beans
    9,374
    Distro
    Xubuntu 14.04 Trusty Tahr

    Re: Lightdm fails at startup

    Hi

    Code:
    [+0.01s] DEBUG: Waiting for ready signal from X server :0 
    [+0.01s] DEBUG: Stopping Plymouth, no displays replace it
    I'm wondering if dbus is not running at this point ? It does not seem to be getting a response from dbus at that point.

    Let's try something.

    Open a terminal and type

    Code:
    sudo nano /etc/init/lightdm.conf
    Look for the line that says

    Code:
    exec lightdm
    before it put a sleep statement so it becomes

    Code:
    sleep 5
    exec lightdm
    Press

    ctrl + o and ctrl + x

    to save and exit.

    This will add a 5 second delay to your boot time.

    Reboot the system.

    Code:
    sudo reboot
    If you still get the same issue, try a delay of 10 and then 15.

    After that give up because i'm wrong

    And thanks because you have inspired me to have a look at the lightdm source code

    EDIT: Doh. I wish you had waited That'll teach me not to refresh a page for an hour or so.

    Kind regards
    Last edited by matt_symes; February 28th, 2013 at 04:04 AM.
    If you believe everything you read, you better not read. ~ Japanese Proverb

    If you don't read the newspaper, you're uninformed. If you read the newspaper, you're mis-informed. - Mark Twain

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  4. #4
    Join Date
    Jan 2013
    Beans
    23

    Re: Lightdm fails at startup

    Hey, thanks a lot for your help! After my second restart, the problem came back, and your solution does work, so it's very fortunate that you posted that! I find the problem itself kinda weird, tho. Technically, it shouldn't be because my computer is slow, I have an i7 3720QM, and I just tried out 1 second delay, and it worked.
    Last edited by jonathanfv; February 28th, 2013 at 06:01 AM.

  5. #5
    Join Date
    May 2010
    Location
    uk
    Beans
    9,374
    Distro
    Xubuntu 14.04 Trusty Tahr

    Re: Lightdm fails at startup

    Hi

    Excellent. I'm glad that helped

    It makes sense of what i was looking at in the source code as well so we both benefited.

    Kind regards
    If you believe everything you read, you better not read. ~ Japanese Proverb

    If you don't read the newspaper, you're uninformed. If you read the newspaper, you're mis-informed. - Mark Twain

    Thinking about becoming an Ubuntu Member?

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