gdm unusable after upgrading to 15.10

[Martin Smith]

Hi there -- I figured I'd try 15.10 a few days before release, and when gdm is the default greeter, I see no login prompt and I have to CTRL-ALT-F1 to get to a terminal. As far as I can tell, there's nothing interesting in the logs in /var/log or /var/log/gdm. I just get a blank, black screen.

As a side note, I'm seeing the error messages described in https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1492764, but I don't think they are the root cause for a missing X-server (AFAICT, there's no X server starting).

Please advice on how I can troubleshoot further. `dkg-reconfigure gdm` and choosing lightdm yields a GUI login prompt in lightdm.

ProblemType: Bug
DistroRelease: Ubuntu 15.10
Package: gdm 3.16.2-0ubuntu2
ProcVersionSignature: Ubuntu 4.2.0-11.13-generic 4.2.1
Uname: Linux 4.2.0-11-generic x86_64
ApportVersion: 2.19-0ubuntu1
Architecture: amd64
Date: Mon Sep 28 20:15:50 2015
InstallationDate: Installed on 2014-07-02 (453 days ago)
InstallationMedia: Ubuntu 14.04 LTS "Trusty Tahr" - Release amd64 (20140417)
SourcePackage: gdm
UpgradeStatus: Upgraded to wily on 2015-09-29 (0 days ago)

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Justin Nichols (jnichols21)]

We're coming up on a month with this issue reported and now post-launch of Wily. Can we get an update on this? Thanks in advance.

[Daniel Elstner (daniel-elstner)]

Interestingly, for me the experience was exactly the other way around: Switching from lightdm to gdm made it work again.
This makes me suspect that the act of switching itself is what makes it work again -- which hints at some configuration issue.

[Evan R (emanguy1)]

When I was fishing around in /etc/gdm/custom.conf I noticed this line:

[daemon]
# Uncomment the line below to force the login screen to use Xorg
#WaylandEnable = false

After doing a bit of research I found this: https://wiki.archlinux.org/index.php/GDM#Use_Xorg_backend which says that by default, GDM 3.16+ uses Wayland as the default display server. I installed the xwayland package and GDM started working again. Apparently xwayland isn't one of GDM's dependencies, given my "apt-cache rdepends gdm" output.

[Justin Nichols (jnichols21)]

Installing xwayland did not seem to solve it for me. Upon reboot, gdm still just loads a grey screen. I cannot even seem to CTRL+ALT+F1 to get to another tty session in order to fix it. I have to boot to recovery, remount as read-write and then dpkg-reconfigure lightdm back to using lightdm.

[JP (vectorpoem)]

"Interestingly, for me the experience was exactly the other way around: Switching from lightdm to gdm made it work again.
This makes me suspect that the act of switching itself is what makes it work again -- which hints at some configuration issue."

This was not the case for me - switching to LightDM and back did not work.

[Tony Mansson (tony-mansson)]

For me the gvm blackscreen could be fixed by installing ubuntu-gnome-desktop and then running "sudo dpkg-reconfigure lightdm". However, this created an endless login loop for all users. The way to fix the endless loop problem was to select the Mate desktop environment before logging in. Then everything worked. Choosing Compiz or Metacity Window Manager keeps you looping.

[Warren (wseverin)]

I, too, have this problem. No login screen after upgrade to 15.10 from 15.04.

I have now spent 36 hours trying to get this upgrade to work. I've tried everything I can find cruising the net. Nothing works. I've gone back and forth between gdm and lightdm. I've uninstalled and reinstalled ubuntu-desktop. All that nonsense and a lot more. I've restored file system backups to the original 15.04 and reapplied the update several times. Nothing in the syslog to suggest the problem.

At this point I give up. I'm going back to 15.04 and will stay there until somebody confirms a fix.

The real fix might just be that Canonical stops with these 6-month releases that don't work and goes to 1-year releases that do.

[Tyler Crandall (tjcrandall-t)]

I found the best "solution" for me was to simply add the latest Mint repo to my sources.list.d/ directory and install the mdm package, which is a fork of gdm, and I've since commented out the minto repo.

mdm has worked without any problems for me. I'll switch back to gdm (or not) when this is working again.

[mjjank (mjjank)]

For me changing form gdm to lightdm worked. Funny, becouse when I was using 15.04 I switched form lightdm to gdm from this same reason.

[Natron (natron-gmx)]

Could someone check if installing this helps?

sudo apt-get install ubuntu-gnome-default-settings

After installing ubuntu-gnome-desktop, gdm did work again. Therefore I tried to find out which exact packet is fixing it for me and ubuntu-gnome-default-settings seems to be the one.

[Natron (natron-gmx)]

I now installed only ubuntu-gnome-default-settings on a second PC with the same problem and changed back to gdm. It worked there as well. So a fix for this problem seems to be contained in this packet.

[JP (vectorpoem)]

(Re)installing ubuntu-gnome-default-settings and then running "sudo dpkg-reconfigure gdm" to switch back to gdm (from lightdm) worked for me.

This is a nasty, renders-system-unusable bug though and it should not be de-prioritized just because there's a workaround that worked for 2 users.

[Dana Goyette (danagoyette)]

More specifically, the critical file from ubuntu-gnome-default-settings is:
/usr/share/glib-2.0/schemas/20_ubuntu-gnome-default-settings.gschema.override

If you remove that file and update schemas (one way is "dpkg-reconfigure libglib2.0-0"), gdm won't start properly.
If you re-add the file and update schemas, gdm starts working.

Also noteworthy: the gdm log file is now (null)-greeter.log instead of :0-greeter.log.

[Hans109h (hans109h)]

I am following this bug as I had some similar oddities after upgrading from U.Gnome 15.04 to 15.10. During the install I elected to keep the existing copy of /etc/gdm/custom.conf because I had made changes to the "list users" section that I wanted to keep.

Today I decided to replace my existing copy with the dpkg-dist copy, and low and behold, using that conf got everything back to normal. Just commenting in case it helps others.

[Huang yun (7415069-1)]

aptitude install adwaita-icon-theme-full

[Huang yun (7415069-1)]

这是一个非常坑爹的 bug 啊，经过很多次的安装、对比和验证，结论是缺少 adwaita-icon-theme-full 包
安装过程：
1、最小安装 Ubuntu 15.10 Server 版（64位）
2、aptitude install xorg xwayland
3、aptitude install gnome-shell gnome-shell-extensions gdm
4、aptitude install gnome-session-wayland
5、aptitude install adwaita-icon-theme-full
6、reboot

......
最小化桌面系统 ok

[Jacob Maher (jake-maher-10)]

I found this bug after trying to swap to GDM on ubuntu 15.10. I have overcome it thanks to people working through this.
It seems that whatever the `ubuntu-gnome-default-settings` package does seems to help also un-comment-ing `WaylandEnable=false` in /etc/gdm/custom.conf is what needs to be done about it

The latter may only be because I use NVIDIA proprietary drivers

[Sto (stojano)]

still an issue... :(

[Tim (darkxst)]

Can anyone still affected by this please attach the output of `journalctl`. Saying that your system boots to a blank screen is not particularly helpful, there there could be numerous reasons causing that, such as hardware specific driver bugs, dependency issues etc.

The recommended way to run GNOME desktop is to install:
sudo apt-get install ubuntu-gnome-desktop^
While installing the bits and pieces standalone should work, it doesnt get anywhere near as much testing as the complete packageset above.

re Wayland comments:
The gdm wayland greeter is not available by default and gdm automatically falls back to the X backend in this case (so no need to mess with custom.conf here). if you want to use gdm wayland or just wayland in general you must install: gnome-session-wayland , xwayland by itself is not enough.

ubuntu-gnome-default-settings:
I have no idea why this package being missing would affect gdm. Though if it is indeed the schema overrides that fixes it perhaps it is caused by the ubuntu overlay scrollbars or otherwise one of the default settings points to a missing file/font perhaps.
This package is pulled in by default when using ubuntu-gnome-desktop

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.