GDMおよびLightdmは、更新後に機能しません。 KDMは大丈夫です
先週の火曜日にUbuntu（apt-get update、apt-get upgrade、apt-get dist-upgrade）を更新した後、GDMは動作を停止し、Ubuntuのロゴで起動が停止しました。 Lightdmも動作しません（同じことが起こります）。コマンドラインからGDMを手動で起動すると、GDMが開き、時間、アクセシビリティオプションなどが表示されますが、ログインとパスワードのフォームはありません。 Lightdmを起動すると、低グラフィックモードで開き、マウスカーソルが表示されません。そのため、TTYコンソールを使用してKDMをインストールしましたが、これは期待どおりに機能します。
GDMとLightdmの両方を削除して再インストールしようとしましたが、成功しませんでした。 /etc/X11/default-display-managerを編集し、dpkg-reconfigureを使用して、dpkg --configure -aも役に立たなかった。
（Xfceデスクトップを備えたUbuntu 14.04があり、ディスプレイマネージャーとしてGDMがありました。Windows7でのデュアルブート。）
これらは役立つと思われるログですが、必要に応じて他のログを投稿できます。
これは、その日に行われた更新をリストするdpkg.logの一部です。
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
GDMをデフォルトとして選択した場合のboot.logの内容：
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 ]
Lightdmをデフォルトとして選択した場合のboot.logの内容：
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 ]
最後に、デフォルトをKDM（動作している唯一のもの）に設定したときのboot.logの内容：
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 ]
どうすれば修正できますか？
gdm.logのコンテンツ（CameronNemoから投稿するように要求されたコンテンツ）をグーグルで検索し、 このリンク で解決策を見つけました。
問題は、おそらく更新中に挿入された/etc/profileの無効な行でした。
[[ -f "/etc/autopackage/paths-bash" ]] && . "/etc/autopackage/paths-bash"
この行にコメントしたところ、GDMが正常に機能するようになりました。
1つのディスプレイマネージャー以外のすべてをパージ（アンインストールではなく）してから、ブートログを記録してください。また、Sudo cat /var/log/upstart/gdm.logの出力を貼り付けていただけますか？
Ubuntu 14でも同じ問題が発生しました。Ctrl+ Alt + f2を使用してログインしました。ファイル「/ etc/profile」を調べたところ、パスの設定中に不正な文字が挿入されていました。それを修正した後、ログオフして再起動しましたが、GDMは完全に機能していました。不正な文字がないかファイルを調べることをお勧めします。