Ubuntu – GDM and Lightdm don’t work after update; KDM is ok

14.04gdmkdmlightdm

After updating Ubuntu (apt-get update, apt-get upgrade and apt-get dist-upgrade) last Tuesday, GDM stopped working, and the startup hangs on the Ubuntu logo. Lightdm also don't work (same happens). If I start GDM manually from commandline, it opens and shows the time, accessibility options, and so on, but with no login and password form; and if I start Lightdm, it opens in low-graphics mode and the mouse cursor doesn't appear. So I used the TTY console to install KDM, which works as expected.

I've tried to purge and reinstall both GDM and Lightdm, but no success.
Editing /etc/X11/default-display-manager, using dpkg-reconfigure, dpkg --configure -a also didn't help.

(I have Ubuntu 14.04 with Xfce desktop and had GDM as display manager. Dual boot with Windows 7.)

These are the logs I believe that can be useful, but I can post other logs if needed:

This is the part of dpkg.log that lists the updates done that day:

2014-05-20 00:33:02 startup archives unpack
2014-05-20 00:33:15 upgrade vlc-plugin-pulse:i386 2.1.2-2build2 2.1.4-0ubuntu14.04.1
2014-05-20 00:33:15 status half-configured vlc-plugin-pulse:i386 2.1.2-2build2
2014-05-20 00:33:15 status unpacked vlc-plugin-pulse:i386 2.1.2-2build2
2014-05-20 00:33:15 status half-installed vlc-plugin-pulse:i386 2.1.2-2build2
2014-05-20 00:33:15 status triggers-pending vlc-nox:i386 2.1.2-2build2
2014-05-20 00:33:15 status half-installed vlc-plugin-pulse:i386 2.1.2-2build2
2014-05-20 00:33:16 status half-installed vlc-plugin-pulse:i386 2.1.2-2build2
2014-05-20 00:33:16 status unpacked vlc-plugin-pulse:i386 2.1.4-0ubuntu14.04.1
2014-05-20 00:33:16 status unpacked vlc-plugin-pulse:i386 2.1.4-0ubuntu14.04.1
2014-05-20 00:33:16 upgrade vlc-plugin-notify:i386 2.1.2-2build2 2.1.4-0ubuntu14.04.1
2014-05-20 00:33:16 status half-configured vlc-plugin-notify:i386 2.1.2-2build2
2014-05-20 00:33:16 status unpacked vlc-plugin-notify:i386 2.1.2-2build2
2014-05-20 00:33:16 status half-installed vlc-plugin-notify:i386 2.1.2-2build2
2014-05-20 00:33:16 status half-installed vlc-plugin-notify:i386 2.1.2-2build2
2014-05-20 00:33:16 status half-installed vlc-plugin-notify:i386 2.1.2-2build2
2014-05-20 00:33:17 status unpacked vlc-plugin-notify:i386 2.1.4-0ubuntu14.04.1
2014-05-20 00:33:17 status unpacked vlc-plugin-notify:i386 2.1.4-0ubuntu14.04.1
2014-05-20 00:33:17 upgrade vlc:i386 2.1.2-2build2 2.1.4-0ubuntu14.04.1
2014-05-20 00:33:17 status half-configured vlc:i386 2.1.2-2build2
2014-05-20 00:33:17 status unpacked vlc:i386 2.1.2-2build2
2014-05-20 00:33:17 status half-installed vlc:i386 2.1.2-2build2
2014-05-20 00:33:17 status triggers-pending mime-support:all 3.54ubuntu1
2014-05-20 00:33:17 status half-installed vlc:i386 2.1.2-2build2
2014-05-20 00:33:18 status triggers-pending man-db:i386 2.6.7.1-1
2014-05-20 00:33:18 status triggers-pending bamfdaemon:i386 0.5.1+14.04.20140409-0ubuntu1
2014-05-20 00:33:18 status half-installed vlc:i386 2.1.2-2build2
2014-05-20 00:33:18 status triggers-pending desktop-file-utils:i386 0.22-1ubuntu1
2014-05-20 00:33:18 status half-installed vlc:i386 2.1.2-2build2
2014-05-20 00:33:18 status triggers-pending gnome-menus:i386 3.10.1-0ubuntu2
2014-05-20 00:33:18 status triggers-pending mime-support:all 3.54ubuntu1
2014-05-20 00:33:18 status half-installed vlc:i386 2.1.2-2build2
2014-05-20 00:33:18 status unpacked vlc:i386 2.1.4-0ubuntu14.04.1
2014-05-20 00:33:18 status unpacked vlc:i386 2.1.4-0ubuntu14.04.1
2014-05-20 00:33:19 upgrade libvlccore7:i386 2.1.2-2build2 2.1.4-0ubuntu14.04.1
2014-05-20 00:33:19 status half-configured libvlccore7:i386 2.1.2-2build2
2014-05-20 00:33:19 status unpacked libvlccore7:i386 2.1.2-2build2
2014-05-20 00:33:19 status half-installed libvlccore7:i386 2.1.2-2build2
2014-05-20 00:33:19 status half-installed libvlccore7:i386 2.1.2-2build2
2014-05-20 00:33:19 status unpacked libvlccore7:i386 2.1.4-0ubuntu14.04.1
2014-05-20 00:33:19 status unpacked libvlccore7:i386 2.1.4-0ubuntu14.04.1
2014-05-20 00:33:20 upgrade vlc-data:all 2.1.2-2build2 2.1.4-0ubuntu14.04.1
2014-05-20 00:33:20 status half-configured vlc-data:all 2.1.2-2build2
2014-05-20 00:33:20 status unpacked vlc-data:all 2.1.2-2build2
2014-05-20 00:33:20 status half-installed vlc-data:all 2.1.2-2build2
2014-05-20 00:33:21 status triggers-pending hicolor-icon-theme:all 0.13-1
2014-05-20 00:33:21 status half-installed vlc-data:all 2.1.2-2build2
2014-05-20 00:33:23 status half-installed vlc-data:all 2.1.2-2build2
2014-05-20 00:33:23 status unpacked vlc-data:all 2.1.4-0ubuntu14.04.1
2014-05-20 00:33:23 status unpacked vlc-data:all 2.1.4-0ubuntu14.04.1
2014-05-20 00:33:24 upgrade vlc-nox:i386 2.1.2-2build2 2.1.4-0ubuntu14.04.1
2014-05-20 00:33:24 status half-configured vlc-nox:i386 2.1.2-2build2
2014-05-20 00:33:24 status unpacked vlc-nox:i386 2.1.2-2build2
2014-05-20 00:33:24 status half-installed vlc-nox:i386 2.1.2-2build2
2014-05-20 00:33:25 status half-installed vlc-nox:i386 2.1.2-2build2
2014-05-20 00:33:25 status unpacked vlc-nox:i386 2.1.4-0ubuntu14.04.1
2014-05-20 00:33:25 status unpacked vlc-nox:i386 2.1.4-0ubuntu14.04.1
2014-05-20 00:33:26 upgrade libvlc5:i386 2.1.2-2build2 2.1.4-0ubuntu14.04.1
2014-05-20 00:33:26 status half-configured libvlc5:i386 2.1.2-2build2
2014-05-20 00:33:26 status unpacked libvlc5:i386 2.1.2-2build2
2014-05-20 00:33:26 status half-installed libvlc5:i386 2.1.2-2build2
2014-05-20 00:33:26 status half-installed libvlc5:i386 2.1.2-2build2
2014-05-20 00:33:26 status unpacked libvlc5:i386 2.1.4-0ubuntu14.04.1
2014-05-20 00:33:26 status unpacked libvlc5:i386 2.1.4-0ubuntu14.04.1
2014-05-20 00:33:27 upgrade network-manager-gnome:i386 0.9.8.8-0ubuntu4 0.9.8.8-0ubuntu4.1
2014-05-20 00:33:27 status half-configured network-manager-gnome:i386 0.9.8.8-0ubuntu4
2014-05-20 00:33:27 status unpacked network-manager-gnome:i386 0.9.8.8-0ubuntu4
2014-05-20 00:33:27 status half-installed network-manager-gnome:i386 0.9.8.8-0ubuntu4
2014-05-20 00:33:27 status triggers-pending gconf2:i386 3.2.6-0ubuntu2
2014-05-20 00:33:27 status half-installed network-manager-gnome:i386 0.9.8.8-0ubuntu4
2014-05-20 00:33:27 status triggers-pending libglib2.0-0:i386 2.40.0-2
2014-05-20 00:33:27 status half-installed network-manager-gnome:i386 0.9.8.8-0ubuntu4
2014-05-20 00:33:27 status half-installed network-manager-gnome:i386 0.9.8.8-0ubuntu4
2014-05-20 00:33:27 status half-installed network-manager-gnome:i386 0.9.8.8-0ubuntu4
2014-05-20 00:33:27 status half-installed network-manager-gnome:i386 0.9.8.8-0ubuntu4
2014-05-20 00:33:28 status half-installed network-manager-gnome:i386 0.9.8.8-0ubuntu4
2014-05-20 00:33:28 status unpacked network-manager-gnome:i386 0.9.8.8-0ubuntu4.1
2014-05-20 00:33:28 status unpacked network-manager-gnome:i386 0.9.8.8-0ubuntu4.1
2014-05-20 00:33:28 upgrade libnm-gtk-dev:i386 0.9.8.8-0ubuntu4 0.9.8.8-0ubuntu4.1
2014-05-20 00:33:28 status half-configured libnm-gtk-dev:i386 0.9.8.8-0ubuntu4
2014-05-20 00:33:28 status unpacked libnm-gtk-dev:i386 0.9.8.8-0ubuntu4
2014-05-20 00:33:28 status half-installed libnm-gtk-dev:i386 0.9.8.8-0ubuntu4
2014-05-20 00:33:28 status half-installed libnm-gtk-dev:i386 0.9.8.8-0ubuntu4
2014-05-20 00:33:28 status unpacked libnm-gtk-dev:i386 0.9.8.8-0ubuntu4.1
2014-05-20 00:33:29 status unpacked libnm-gtk-dev:i386 0.9.8.8-0ubuntu4.1
2014-05-20 00:33:29 upgrade libnm-gtk0:i386 0.9.8.8-0ubuntu4 0.9.8.8-0ubuntu4.1
2014-05-20 00:33:29 status half-configured libnm-gtk0:i386 0.9.8.8-0ubuntu4
2014-05-20 00:33:29 status unpacked libnm-gtk0:i386 0.9.8.8-0ubuntu4
2014-05-20 00:33:29 status half-installed libnm-gtk0:i386 0.9.8.8-0ubuntu4
2014-05-20 00:33:29 status half-installed libnm-gtk0:i386 0.9.8.8-0ubuntu4
2014-05-20 00:33:29 status unpacked libnm-gtk0:i386 0.9.8.8-0ubuntu4.1
2014-05-20 00:33:29 status unpacked libnm-gtk0:i386 0.9.8.8-0ubuntu4.1
2014-05-20 00:33:30 upgrade libnm-gtk-common:all 0.9.8.8-0ubuntu4 0.9.8.8-0ubuntu4.1
2014-05-20 00:33:30 status half-configured libnm-gtk-common:all 0.9.8.8-0ubuntu4
2014-05-20 00:33:30 status unpacked libnm-gtk-common:all 0.9.8.8-0ubuntu4
2014-05-20 00:33:30 status half-installed libnm-gtk-common:all 0.9.8.8-0ubuntu4
2014-05-20 00:33:30 status half-installed libnm-gtk-common:all 0.9.8.8-0ubuntu4
2014-05-20 00:33:30 status unpacked libnm-gtk-common:all 0.9.8.8-0ubuntu4.1
2014-05-20 00:33:30 status unpacked libnm-gtk-common:all 0.9.8.8-0ubuntu4.1
2014-05-20 00:33:30 upgrade gir1.2-nmgtk-1.0:i386 0.9.8.8-0ubuntu4 0.9.8.8-0ubuntu4.1
2014-05-20 00:33:30 status half-configured gir1.2-nmgtk-1.0:i386 0.9.8.8-0ubuntu4
2014-05-20 00:33:31 status unpacked gir1.2-nmgtk-1.0:i386 0.9.8.8-0ubuntu4
2014-05-20 00:33:31 status half-installed gir1.2-nmgtk-1.0:i386 0.9.8.8-0ubuntu4
2014-05-20 00:33:31 status half-installed gir1.2-nmgtk-1.0:i386 0.9.8.8-0ubuntu4
2014-05-20 00:33:31 status unpacked gir1.2-nmgtk-1.0:i386 0.9.8.8-0ubuntu4.1
2014-05-20 00:33:31 status unpacked gir1.2-nmgtk-1.0:i386 0.9.8.8-0ubuntu4.1
2014-05-20 00:33:31 trigproc mime-support:all 3.54ubuntu1 3.54ubuntu1
2014-05-20 00:33:31 status half-configured mime-support:all 3.54ubuntu1
2014-05-20 00:33:36 status installed mime-support:all 3.54ubuntu1
2014-05-20 00:33:36 trigproc man-db:i386 2.6.7.1-1 2.6.7.1-1
2014-05-20 00:33:36 status half-configured man-db:i386 2.6.7.1-1
2014-05-20 00:33:39 status installed man-db:i386 2.6.7.1-1
2014-05-20 00:33:39 trigproc bamfdaemon:i386 0.5.1+14.04.20140409-0ubuntu1 0.5.1+14.04.20140409-0ubuntu1
2014-05-20 00:33:39 status half-configured bamfdaemon:i386 0.5.1+14.04.20140409-0ubuntu1
2014-05-20 00:33:39 status installed bamfdaemon:i386 0.5.1+14.04.20140409-0ubuntu1
2014-05-20 00:33:39 trigproc desktop-file-utils:i386 0.22-1ubuntu1 0.22-1ubuntu1
2014-05-20 00:33:39 status half-configured desktop-file-utils:i386 0.22-1ubuntu1
2014-05-20 00:33:40 status installed desktop-file-utils:i386 0.22-1ubuntu1
2014-05-20 00:33:40 trigproc gnome-menus:i386 3.10.1-0ubuntu2 3.10.1-0ubuntu2
2014-05-20 00:33:40 status half-configured gnome-menus:i386 3.10.1-0ubuntu2
2014-05-20 00:33:40 status installed gnome-menus:i386 3.10.1-0ubuntu2
2014-05-20 00:33:40 trigproc hicolor-icon-theme:all 0.13-1 0.13-1
2014-05-20 00:33:40 status half-configured hicolor-icon-theme:all 0.13-1
2014-05-20 00:33:45 status installed hicolor-icon-theme:all 0.13-1
2014-05-20 00:33:45 trigproc gconf2:i386 3.2.6-0ubuntu2 3.2.6-0ubuntu2
2014-05-20 00:33:45 status half-configured gconf2:i386 3.2.6-0ubuntu2
2014-05-20 00:33:45 status installed gconf2:i386 3.2.6-0ubuntu2
2014-05-20 00:33:45 trigproc libglib2.0-0:i386 2.40.0-2 2.40.0-2
2014-05-20 00:33:45 status half-configured libglib2.0-0:i386 2.40.0-2
2014-05-20 00:33:47 status installed libglib2.0-0:i386 2.40.0-2
2014-05-20 00:33:47 startup packages configure
2014-05-20 00:33:47 configure vlc-data:all 2.1.4-0ubuntu14.04.1 <none>
2014-05-20 00:33:47 status unpacked vlc-data:all 2.1.4-0ubuntu14.04.1
2014-05-20 00:33:47 status half-configured vlc-data:all 2.1.4-0ubuntu14.04.1
2014-05-20 00:33:48 status installed vlc-data:all 2.1.4-0ubuntu14.04.1
2014-05-20 00:33:48 configure libvlccore7:i386 2.1.4-0ubuntu14.04.1 <none>
2014-05-20 00:33:48 status unpacked libvlccore7:i386 2.1.4-0ubuntu14.04.1
2014-05-20 00:33:48 status half-configured libvlccore7:i386 2.1.4-0ubuntu14.04.1
2014-05-20 00:33:48 status installed libvlccore7:i386 2.1.4-0ubuntu14.04.1
2014-05-20 00:33:48 status triggers-pending libc-bin:i386 2.19-0ubuntu6
2014-05-20 00:33:48 configure libvlc5:i386 2.1.4-0ubuntu14.04.1 <none>
2014-05-20 00:33:48 status unpacked libvlc5:i386 2.1.4-0ubuntu14.04.1
2014-05-20 00:33:48 status half-configured libvlc5:i386 2.1.4-0ubuntu14.04.1
2014-05-20 00:33:48 status installed libvlc5:i386 2.1.4-0ubuntu14.04.1
2014-05-20 00:33:48 configure vlc-nox:i386 2.1.4-0ubuntu14.04.1 <none>
2014-05-20 00:33:48 status unpacked vlc-nox:i386 2.1.4-0ubuntu14.04.1
2014-05-20 00:33:48 status half-configured vlc-nox:i386 2.1.4-0ubuntu14.04.1
2014-05-20 00:33:48 status installed vlc-nox:i386 2.1.4-0ubuntu14.04.1
2014-05-20 00:33:48 configure vlc-plugin-pulse:i386 2.1.4-0ubuntu14.04.1 <none>
2014-05-20 00:33:48 status unpacked vlc-plugin-pulse:i386 2.1.4-0ubuntu14.04.1
2014-05-20 00:33:48 status half-configured vlc-plugin-pulse:i386 2.1.4-0ubuntu14.04.1
2014-05-20 00:33:48 status installed vlc-plugin-pulse:i386 2.1.4-0ubuntu14.04.1
2014-05-20 00:33:48 configure vlc-plugin-notify:i386 2.1.4-0ubuntu14.04.1 <none>
2014-05-20 00:33:48 status unpacked vlc-plugin-notify:i386 2.1.4-0ubuntu14.04.1
2014-05-20 00:33:48 status half-configured vlc-plugin-notify:i386 2.1.4-0ubuntu14.04.1
2014-05-20 00:33:48 status installed vlc-plugin-notify:i386 2.1.4-0ubuntu14.04.1
2014-05-20 00:33:48 configure vlc:i386 2.1.4-0ubuntu14.04.1 <none>
2014-05-20 00:33:48 status unpacked vlc:i386 2.1.4-0ubuntu14.04.1
2014-05-20 00:33:49 status half-configured vlc:i386 2.1.4-0ubuntu14.04.1
2014-05-20 00:33:49 status installed vlc:i386 2.1.4-0ubuntu14.04.1
2014-05-20 00:33:49 configure libnm-gtk-common:all 0.9.8.8-0ubuntu4.1 <none>
2014-05-20 00:33:49 status unpacked libnm-gtk-common:all 0.9.8.8-0ubuntu4.1
2014-05-20 00:33:49 status half-configured libnm-gtk-common:all 0.9.8.8-0ubuntu4.1
2014-05-20 00:33:49 status installed libnm-gtk-common:all 0.9.8.8-0ubuntu4.1
2014-05-20 00:33:49 configure libnm-gtk0:i386 0.9.8.8-0ubuntu4.1 <none>
2014-05-20 00:33:49 status unpacked libnm-gtk0:i386 0.9.8.8-0ubuntu4.1
2014-05-20 00:33:49 status half-configured libnm-gtk0:i386 0.9.8.8-0ubuntu4.1
2014-05-20 00:33:49 status installed libnm-gtk0:i386 0.9.8.8-0ubuntu4.1
2014-05-20 00:33:49 configure network-manager-gnome:i386 0.9.8.8-0ubuntu4.1 <none>
2014-05-20 00:33:49 status unpacked network-manager-gnome:i386 0.9.8.8-0ubuntu4.1
2014-05-20 00:33:49 status unpacked network-manager-gnome:i386 0.9.8.8-0ubuntu4.1
2014-05-20 00:33:49 status half-configured network-manager-gnome:i386 0.9.8.8-0ubuntu4.1
2014-05-20 00:33:49 status installed network-manager-gnome:i386 0.9.8.8-0ubuntu4.1
2014-05-20 00:33:49 configure gir1.2-nmgtk-1.0:i386 0.9.8.8-0ubuntu4.1 <none>
2014-05-20 00:33:49 status unpacked gir1.2-nmgtk-1.0:i386 0.9.8.8-0ubuntu4.1
2014-05-20 00:33:49 status half-configured gir1.2-nmgtk-1.0:i386 0.9.8.8-0ubuntu4.1
2014-05-20 00:33:49 status installed gir1.2-nmgtk-1.0:i386 0.9.8.8-0ubuntu4.1
2014-05-20 00:33:49 configure libnm-gtk-dev:i386 0.9.8.8-0ubuntu4.1 <none>
2014-05-20 00:33:49 status unpacked libnm-gtk-dev:i386 0.9.8.8-0ubuntu4.1
2014-05-20 00:33:49 status half-configured libnm-gtk-dev:i386 0.9.8.8-0ubuntu4.1
2014-05-20 00:33:49 status installed libnm-gtk-dev:i386 0.9.8.8-0ubuntu4.1
2014-05-20 00:33:49 trigproc libc-bin:i386 2.19-0ubuntu6 <none>
2014-05-20 00:33:49 status half-configured libc-bin:i386 2.19-0ubuntu6
2014-05-20 00:33:50 status installed libc-bin:i386 2.19-0ubuntu6

Contents of boot.log when I select GDM as default:

resume: libgcrypt version: 1.5.3
 * Starting Mount filesystems on boot [ OK ]
 * Starting Fix-up sensitive /proc filesystem entries [ OK ]
 * Starting Populate /dev filesystem [ OK ]
 * Starting Populate and link to /run filesystem [ OK ]
 * Stopping Fix-up sensitive /proc filesystem entries [ OK ]
 * Stopping Populate /dev filesystem [ OK ]
 * Stopping Populate and link to /run filesystem [ OK ]
 * Stopping Track if upstart is running in a container [ OK ]
 * Starting Initialize or finalize resolvconf [ OK ]
 * Starting set console keymap [ OK ]
 * Starting Signal sysvinit that virtual filesystems are mounted [ OK ]
 * Starting Signal sysvinit that virtual filesystems are mounted [ OK ]
 * Starting set sysctls from /etc/sysctl.conf [ OK ]
 * Starting Bridge udev events into upstart [ OK ]
 * Stopping set console keymap [ OK ]
 * Starting Signal sysvinit that remote filesystems are mounted [ OK ]
 * Stopping set sysctls from /etc/sysctl.conf [ OK ]
 * Starting device node and kernel event manager [ OK ]
 * Starting load modules from /etc/modules [ OK ]
 * Starting cold plug devices [ OK ]
 * Starting log initial device creation [ OK ]
 * Stopping load modules from /etc/modules [ OK ]
 * Starting configure network device security [ OK ]
 * Starting configure network device security [ OK ]
 * Starting Mount network filesystems [ OK ]
 * Stopping Mount network filesystems [ OK ]
 * Starting Bridge socket events into upstart [ OK ]
 * Starting Signal sysvinit that the rootfs is mounted [ OK ]
 * Starting configure network device [ OK ]
 * Starting Uncomplicated firewall [ OK ]
 * Starting configure network device [ OK ]
 * Starting Clean /tmp directory [ OK ]
 * Stopping Clean /tmp directory [ OK ]
 * Stopping Read required files in advance (for other mountpoints) [ OK ]
 * Stopping cold plug devices [ OK ]
 * Stopping log initial device creation [ OK ]
 * Starting enable remaining boot-time encrypted block devices [ OK ]
 * Starting Signal sysvinit that local filesystems are mounted [ OK ]
 * Starting restore software rfkill state [ OK ]
 * Starting SMB/CIFS File Server [ OK ]
 * Starting configure network device security [ OK ]
 * Stopping Mount filesystems on boot [ OK ]
 * Stopping restore software rfkill state [ OK ]
 * Starting Enabling additional executable binary formats [ OK ]
 * Starting flush early job output to logs [ OK ]
 * Stopping Failsafe Boot Delay [ OK ]
 * Starting System V initialisation compatibility [ OK ]
 * Stopping flush early job output to logs [ OK ]
 * Starting configure virtual network devices [ OK ]
 * Starting Bridge file events into upstart [ OK ]
 * Starting early crypto disks...         
 [ OK ]
 * Starting system logging daemon [ OK ]
Skipping profile in /etc/apparmor.d/disable: usr.bin.firefox
Skipping profile in /etc/apparmor.d/disable: usr.sbin.rsyslogd
 * Starting AppArmor profiles         
 [ OK ]
 * Setting sensors limits         
 [ OK ]
 * Starting SMB/CIFS File and Active Directory Server [ OK ]
 * Starting D-Bus system message bus [ OK ]
 * Stopping System V initialisation compatibility [ OK ]
 * Starting modem connection manager [ OK ]
 * Starting configure network device security [ OK ]
 * Starting SystemD login management service [ OK ]
 * Starting System V runlevel compatibility [ OK ]
 * Starting GNOME Display Manager [ OK ]
 * Starting ACPI daemon [ OK ]
 * Starting anac(h)ronistic cron [ OK ]
 * Starting K Display Manager [ OK ]
 * Starting save kernel messages [ OK ]
 * Starting regular background program processing daemon [ OK ]
 * Starting deferred execution scheduler [ OK ]
 * Stopping save kernel messages [ OK ]
 * Stopping anac(h)ronistic cron [ OK ]
 * Starting bluetooth daemon [ OK ]
 * Starting crash report submission daemon [ OK ]
 * speech-dispatcher disabled; edit /etc/default/speech-dispatcher
 * Stopping CPU interrupts balancing daemon [ OK ]
 * Starting GNOME Display Manager [ fail ]
 * Starting automatic crash report generation [ OK ]
 * Starting cups-browsed - Bonjour remote printer browsing daemon [ OK ]
 * Stopping Restore Sound Card State [ OK ]
 * Starting SMB/CIFS File and Active Directory Server [ fail ]
 * Stopping Send an event to indicate plymouth is up [ OK ]
 * Stopping K Display Manager [ OK ]
 * Starting network connection manager [ OK ]
Starting VirtualBox kernel modules * Starting CUPS printing spooler/server [ OK ]
 * Starting Samba Auto-reload Integration [ OK ]
 * Stopping Samba Auto-reload Integration [ OK ]
 ...done.
 * Starting NTP server ntpd         
 [ OK ]
saned disabled; edit /etc/default/saned
 * Stopping System V runlevel compatibility [ OK ]
 * Stopping TeamViewer remote control daemon [ OK ]
 * Starting Mount network filesystems [ OK ]
 * Starting Samba Winbind [ OK ]
 * Stopping Mount network filesystems [ OK ]
 * Starting NetBIOS name server [ OK ]
 * Stopping LightDM Display Manager [ OK ]
 * Stopping Read required files in advance [ OK ]

Contents of boot.log when I select Lightdm as default:

resume: libgcrypt version: 1.5.3
 * Stopping Read required files in advance [ OK ]
 * Starting Mount filesystems on boot [ OK ]
 * Starting Populate and link to /run filesystem [ OK ]
 * Stopping Populate and link to /run filesystem [ OK ]
 * Starting Initialize or finalize resolvconf [ OK ]
 * Stopping Track if upstart is running in a container [ OK ]
 * Starting Signal sysvinit that virtual filesystems are mounted [ OK ]
 * Starting Signal sysvinit that virtual filesystems are mounted [ OK ]
 * Starting Bridge udev events into upstart [ OK ]
 * Starting Signal sysvinit that remote filesystems are mounted [ OK ]
 * Starting device node and kernel event manager [ OK ]
 * Starting load modules from /etc/modules [ OK ]
 * Starting cold plug devices [ OK ]
 * Starting log initial device creation [ OK ]
 * Stopping load modules from /etc/modules [ OK ]
 * Starting Signal sysvinit that the rootfs is mounted [ OK ]
 * Starting Clean /tmp directory [ OK ]
 * Starting configure network device security [ OK ]
 * Stopping Clean /tmp directory [ OK ]
 * Starting Uncomplicated firewall [ OK ]
 * Starting configure network device [ OK ]
 * Starting configure network device security [ OK ]
 * Starting Mount network filesystems [ OK ]
 * Stopping Mount network filesystems [ OK ]
 * Starting configure network device [ OK ]
 * Starting Bridge socket events into upstart [ OK ]
 * Stopping cold plug devices [ OK ]
 * Stopping log initial device creation [ OK ]
 * Starting enable remaining boot-time encrypted block devices [ OK ]
 * Stopping Read required files in advance (for other mountpoints) [ OK ]
 * Starting SMB/CIFS File Server [ OK ]
 * Starting Signal sysvinit that local filesystems are mounted [ OK ]
 * Starting configure network device security [ OK ]
 * Stopping Mount filesystems on boot [ OK ]
 * Starting Enabling additional executable binary formats [ OK ]
 * Starting flush early job output to logs [ OK ]
 * Stopping Failsafe Boot Delay [ OK ]
 * Starting D-Bus system message bus [ OK ]
 * Starting System V initialisation compatibility [ OK ]
 * Stopping flush early job output to logs [ OK ]
 * Starting modem connection manager [ OK ]
 * Starting configure network device security [ OK ]
 * Starting early crypto disks...         
 [ OK ]
 * Starting bluetooth daemon [ OK ]
 * Starting configure virtual network devices [ OK ]
 * Starting system logging daemon [ OK ]
 * Starting SystemD login management service [ OK ]
 * Starting Bridge file events into upstart [ OK ]
 * Starting SMB/CIFS File and Active Directory Server [ OK ]
Skipping profile in /etc/apparmor.d/disable: usr.bin.firefox
Skipping profile in /etc/apparmor.d/disable: usr.sbin.rsyslogd
 * Starting AppArmor profiles         
 [ OK ]
 * Starting network connection manager [ OK ]
 * Starting SMB/CIFS File and Active Directory Server [ fail ]
 * Setting sensors limits        * Starting CUPS printing spooler/server [ OK ]

 [ OK ]
 * Starting Samba Auto-reload Integration [ OK ]
 * Stopping Samba Auto-reload Integration [ OK ]
 * Starting cups-browsed - Bonjour remote printer browsing daemon [ OK ]
 * Stopping System V initialisation compatibility [ OK ]
 * speech-dispatcher disabled; edit /etc/default/speech-dispatcher
 * Starting System V runlevel compatibility [ OK ]
 * Starting ACPI daemon [ OK ]
 * Starting anac(h)ronistic cron [ OK ]
 * Starting K Display Manager [ OK ]
 * Starting save kernel messages [ OK ]
 * Starting crash report submission daemon [ OK ]
 * Starting regular background program processing daemon [ OK ]
 * Starting deferred execution scheduler [ OK ]
 * Stopping save kernel messages [ OK ]
 * Stopping anac(h)ronistic cron [ OK ]
 * Stopping CPU interrupts balancing daemon [ OK ]
 * Starting automatic crash report generation [ OK ]
 * Stopping Restore Sound Card State [ OK ]
 * Stopping Send an event to indicate plymouth is up [ OK ]
 * Stopping TeamViewer remote control daemon [ OK ]
 * Stopping K Display Manager [ OK ]
 * Starting Mount network filesystems [ OK ]
 * Starting Samba Winbind [ OK ]
 * Stopping Mount network filesystems [ OK ]
 * Starting NetBIOS name server [ OK ]
Starting VirtualBox kernel modules ...done.
 * Starting NTP server ntpd         
 [ OK ]
saned disabled; edit /etc/default/saned
 * Stopping System V runlevel compatibility [ OK ]
 * Stopping LightDM Display Manager [ OK ]

Finally, contents of boot.log when I set the default to KDM (the only one that is working):

resume: libgcrypt version: 1.5.3
 * Stopping Read required files in advance [ OK ]
 * Starting Mount filesystems on boot [ OK ]
 * Starting Populate /dev filesystem [ OK ]
 * Starting Populate and link to /run filesystem [ OK ]
 * Stopping Populate /dev filesystem [ OK ]
 * Stopping Populate and link to /run filesystem [ OK ]
 * Stopping Track if upstart is running in a container [ OK ]
 * Starting Initialize or finalize resolvconf [ OK ]
 * Starting set console keymap [ OK ]
 * Starting Signal sysvinit that virtual filesystems are mounted [ OK ]
 * Starting Signal sysvinit that virtual filesystems are mounted [ OK ]
 * Starting Bridge udev events into upstart [ OK ]
 * Stopping set console keymap [ OK ]
 * Starting Signal sysvinit that remote filesystems are mounted [ OK ]
 * Starting device node and kernel event manager [ OK ]
 * Starting load modules from /etc/modules [ OK ]
 * Starting cold plug devices [ OK ]
 * Starting log initial device creation [ OK ]
 * Stopping load modules from /etc/modules [ OK ]
 * Starting configure network device security [ OK ]
 * Starting Signal sysvinit that the rootfs is mounted [ OK ]
 * Stopping Read required files in advance (for other mountpoints) [ OK ]
 * Starting Clean /tmp directory [ OK ]
 * Stopping Clean /tmp directory [ OK ]
 * Starting Uncomplicated firewall [ OK ]
 * Starting configure network device [ OK ]
 * Stopping Read required files in advance (for other mountpoints) [ OK ]
 * Starting Signal sysvinit that local filesystems are mounted [ OK ]
 * Stopping Mount filesystems on boot [ OK ]
 * Starting Enabling additional executable binary formats [ OK ]
 * Starting flush early job output to logs [ OK ]
 * Starting configure network device security [ OK ]
 * Starting D-Bus system message bus [ OK ]
 * Stopping flush early job output to logs [ OK ]
 * Starting SystemD login management service [ OK ]
 * Starting bluetooth daemon [ OK ]
 * Starting system logging daemon [ OK ]
 * Starting Mount network filesystems [ OK ]
 * Starting Failsafe Boot Delay [ OK ]
 * Starting SMB/CIFS File Server [ OK ]
 * Stopping Failsafe Boot Delay [ OK ]
 * Stopping Mount network filesystems [ OK ]
 * Starting System V initialisation compatibility [ OK ]
 * Starting modem connection manager [ OK ]
 * Starting configure network device security [ OK ]
 * Starting configure network device [ OK ]
 * Starting early crypto disks...         
 [ OK ]
 * Starting Bridge file events into upstart [ OK ]
 * Starting Bridge socket events into upstart [ OK ]
Skipping profile in /etc/apparmor.d/disable: usr.bin.firefox
Skipping profile in /etc/apparmor.d/disable: usr.sbin.rsyslogd
 * Starting AppArmor profiles         
 [ OK ]
 * Setting sensors limits         
 [ OK ]
 * Starting network connection manager [ OK ]
 * Starting SMB/CIFS File and Active Directory Server [ OK ]
 * Starting CUPS printing spooler/server [ OK ]
 * Stopping cold plug devices [ OK ]
 * Stopping System V initialisation compatibility [ OK ]
 * Starting Samba Auto-reload Integration [ OK ]

How can I fix this?

Best Answer

I've googled the content of gdm.log (whose contents CameronNemo asked me to post) and found out the solution in this link.

The problem was an invalid line in /etc/profile probably inserted during an update:

[[ -f "/etc/autopackage/paths-bash" ]] && . "/etc/autopackage/paths-bash"

I just commented this line and now GDM is working properly.

Related Question