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Thread: Black screen after login after 18.04 > 20.04 upgrade (on virtualbox)

  1. #1
    Join Date
    Sep 2006
    Location
    Bucharest, Romania
    Beans
    44
    Distro
    Kubuntu 6.10 Edgy

    Black screen after login after 18.04 > 20.04 upgrade (on virtualbox)

    Hi,

    I was happily running Ubuntu 18.04 (64 bit) in a VirtualBox VM (Windows 10 being the host), and today I decided to upgrade to 20.04. So after an upgrade check, when Ubuntu told me I could upgrade, I decided to do it, and after the upgrade was done and a reboot, I got the login screen. After logging in, the screen went black. Yay!

    I tried to reinstall the VirtualBox guest additions CD. Unfortunately, inserting the drive from VirtualBox doesn't work; shared folders worked, however, so I unpacked the ISO in a shared folder and ran VBoxLinuxAdditions.run from there. After a reboot, I still get the black screen.

    In Xorg.0.log I see this error:

    Code:
    [    26.488] (EE) Failed to load module "vboxvideo" (module does not exist, 0)
    Then later:
    Code:
    [    26.656] (EE) modeset(0): glamor initialization failed
    With 'ps axf', I see this process tree for the X server:

    Code:
       1941 ?        SLsl   0:00 /usr/sbin/lightdm
       1974 tty7     Ssl+   0:02  \_ /usr/lib/xorg/Xorg -core :0 -seat seat0 -auth /var/run/lightdm/root/:0 -nolisten tcp vt7 -novtswitch
       2204 ?        Sl     0:00  \_ lightdm --session-child 12 19
       2274 ?        Ss     0:00      \_ /bin/bash /usr/sbin/lightdm-session /usr/lib/gnome-flashback/gnome-flashback-metacity
       2383 ?        S      0:00          \_ xhost +si:localuser:stefan
    Maybe xhost is hanging there? If I try to strace the process, it seems to be blocked reading something.

    I was using gnome-flashback previously, maybe that can lead to problems?

    EDIT: I can get to X if I boot the previous kernel, the one from 18.04 (from the grub menu I went to Advanced and selected the second kernel).
    Last edited by phormion; October 7th, 2020 at 01:50 PM.

  2. #2
    Join Date
    Sep 2006
    Location
    Bucharest, Romania
    Beans
    44
    Distro
    Kubuntu 6.10 Edgy

    Re: Black screen after login after 18.04 > 20.04 upgrade (on virtualbox)

    The problem seems to have fixed itself after a very usual VirtualBox workaround: power off the VM and power it back on. This always seems to act differently than a restart, and maybe it makes sense - the power off and on sequence probably starts a new VM process. Now I can boot the latest kernel fine (though I'm somewhat reluctant to reboot again ). I'll monitor this and mark the problem as fixed if all goes well.

  3. #3
    Join Date
    Nov 2012
    Location
    Halloween Town
    Beans
    Hidden!
    Distro
    Xubuntu Development Release

    Re: Black screen after login after 18.04 > 20.04 upgrade (on virtualbox)

    Thread moved to Virtualisation.

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