Bug#800327: gdm3: greeter does not start on nvidia

[Bart Vanhaute]

Package: gdm3
Version: 3.14.2-2
Severity: important

After a recent update, the greeter for gdm3 does not start anymore. Instead the
infamous 'Oh no something went wrong" is displayed, with a "Logout" button that
cycles back to that same error page.

When I configure automatic login, I get a working session, so gnome-session
appears to be working correctly.

I did some debugging, and found out that /usr/lib/gnome-session/gnome-session-
check-accelerated-helper fails. I ran the program under strace as user Debian-
gdm and noticed the following :

stat("/dev/nvidiactl", {st_mode=S_IFCHR|0660, st_rdev=makedev(195, 255), ...})
= 0
open("/dev/nvidiactl", O_RDWR)          = -1 EACCES (Permission denied)


So it looks like that device is not accessible for user Debian-gdm

$ ls -l /dev/nvidiactl
crw-rw---- 1 root video 195, 255 Sep 27 21:16 /dev/nvidiactl
$ groups Debian-gdm
Debian-gdm : Debian-gdm


Adding the user Debian-gdm to group video fixes the problem.



-- System Information:
Debian Release: stretch/sid
  APT prefers unstable
  APT policy: (500, 'unstable'), (1, 'experimental')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 4.2.0-1-amd64 (SMP w/8 CPU cores)
Locale: LANG=en_GB.UTF-8, LC_CTYPE=en_GB.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages gdm3 depends on:
ii  accountsservice                       0.6.40-3
ii  adduser                               3.113+nmu3
ii  dconf-cli                             0.24.0-2
ii  dconf-gsettings-backend               0.24.0-2
ii  debconf [debconf-2.0]                 1.5.57
ii  gir1.2-gdm3                           3.14.2-2
ii  gnome-session [x-session-manager]     3.16.0-1
ii  gnome-session-bin                     3.16.0-1
ii  gnome-settings-daemon                 3.16.3-1
ii  gnome-shell                           3.16.3-2
ii  gnome-terminal [x-terminal-emulator]  3.18.0-1
ii  gsettings-desktop-schemas             3.18.0-1
ii  libaccountsservice0                   0.6.40-3
ii  libaudit1                             1:2.4.4-3+b1
ii  libc6                                 2.19-22
ii  libcanberra-gtk3-0                    0.30-2.1
ii  libcanberra0                          0.30-2.1
ii  libgdk-pixbuf2.0-0                    2.32.0-1
ii  libgdm1                               3.14.2-2
ii  libglib2.0-0                          2.46.0-1
ii  libglib2.0-bin                        2.46.0-1
ii  libgtk-3-0                            3.16.6-1
ii  libpam-modules                        1.1.8-3.1
ii  libpam-runtime                        1.1.8-3.1
ii  libpam-systemd                        226-3
ii  libpam0g                              1.1.8-3.1
ii  librsvg2-common                       2.40.10-1
ii  libselinux1                           2.3-2+b1
ii  libsystemd0                           226-3
ii  libwrap0                              7.6.q-25
ii  libx11-6                              2:1.6.3-1
ii  libxau6                               1:1.0.8-1
ii  libxdmcp6                             1:1.1.2-1
ii  libxrandr2                            2:1.5.0-1
ii  lsb-base                              9.20150917
ii  metacity [x-window-manager]           1:3.17.2-4
ii  mutter [x-window-manager]             3.16.3-1
ii  policykit-1                           0.105-12
ii  tinywm [x-window-manager]             1.3-9
ii  twm [x-window-manager]                1:1.0.9-1
ii  ucf                                   3.0030
ii  x11-common                            1:7.7+9
ii  x11-xserver-utils                     7.7+5
ii  xterm [x-terminal-emulator]           320-1

Versions of packages gdm3 recommends:
ii  at-spi2-core               2.16.0-1
ii  desktop-base               8.0.2
ii  gnome-icon-theme           3.12.0-1
ii  gnome-icon-theme-symbolic  3.12.0-1
ii  x11-xkb-utils              7.7+2
ii  xserver-xephyr             2:1.17.2-1.1
ii  xserver-xorg               1:7.7+9
ii  zenity                     3.18.0-1

Versions of packages gdm3 suggests:
ii  gnome-orca            3.16.2-2
ii  libpam-gnome-keyring  3.16.0-4

-- debconf information:
  gdm3/daemon_name: /usr/sbin/gdm3
* shared/default-x-display-manager: gdm3