今天我启动Ubuntu时，它没有启动lightdm，显示黑屏。我切换到控制台Ctrl-Alt-F1并尝试lightdm手动启动
sudo start lightdm
它把我带到图形控制台（Ctrl-Alt-F7），并显示相同的黑屏。此外，它看起来像是启动了，控制台返回了进程数，
lightdm start/running, process 3616
然而，之后
sudo stop lightdm
我有
stop: unknown instance
然后我开始gdm
sudo start gdm
并gdm开始正常。因此，问题出在lightdm。
为了解决这个问题，我尝试清除lightdm并重新安装它
sudo apt-get purge lightdm
sudo apt-get install lightdm
和
sudo apt-get install --reinstall lightdm
这两种方法都无济于事。
现在我正在使用，但如果可能的话，gdm我想恢复。lightdm
谢谢大家的帮助！
附言：我最近没有安装任何附加驱动程序（并且根本没有 NVidia 卡）。
PPS：一些附加信息
$ sudo start lightdm
lightdm start/running, process 2466
$ dmesg | grep lightdm
[ 18.284992] init: lightdm main process (1446) killed by TERM signal
[ 57.691273] init: lightdm main process (2466) terminated with status 1
$ sudo start lightdm
lightdm start/running, process 8140
$ sudo cat /var/log/lightdm/lightdm.log
[+0.00s] DEBUG: Logging to /var/log/lightdm/lightdm.log
[+0.00s] DEBUG: Starting Light Display Manager 1.2.3, UID=0 PID=8140
[+0.00s] DEBUG: Loading configuration from /etc/lightdm/lightdm.conf
[+0.00s] DEBUG: Using D-Bus name org.freedesktop.DisplayManager
[+0.00s] DEBUG: Registered seat module xlocal
[+0.00s] DEBUG: Registered seat module xremote
[+0.00s] DEBUG: Adding default seat
[+0.00s] DEBUG: Starting seat
[+0.00s] DEBUG: Starting new display for automatic login as user stas
[+0.00s] DEBUG: Starting local X display
[+0.00s] DEBUG: Using VT 7
[+0.00s] DEBUG: Activating VT 7
[+0.01s] DEBUG: Logging to /var/log/lightdm/x-0.log
[+0.01s] DEBUG: Writing X server authority to /var/run/lightdm/root/:0
[+0.01s] DEBUG: Launching X Server
[+0.01s] DEBUG: Launching process 8145: /usr/bin/X :0 -auth /var/run/lightdm/root/:0 -nolisten tcp vt7 -novtswitch
[+0.01s] DEBUG: Waiting for ready signal from X server :0
[+0.01s] DEBUG: Acquired bus name org.freedesktop.DisplayManager
[+0.01s] DEBUG: Registering seat with bus path /org/freedesktop/DisplayManager/Seat0
[+0.03s] DEBUG: Process 8145 exited with return value 1
[+0.03s] DEBUG: X server stopped
[+0.03s] DEBUG: Removing X server authority /var/run/lightdm/root/:0
[+0.03s] DEBUG: Releasing VT 7
[+0.03s] DEBUG: Display server stopped
[+0.03s] DEBUG: Stopping display
[+0.03s] DEBUG: Display stopped
[+0.03s] DEBUG: Stopping X local seat, failed to start a display
[+0.03s] DEBUG: Stopping seat
[+0.03s] DEBUG: Seat stopped
[+0.03s] DEBUG: Required seat has stopped
[+0.03s] DEBUG: Stopping display manager
[+0.03s] DEBUG: Display manager stopped
[+0.03s] DEBUG: Stopping daemon
[+0.03s] DEBUG: Exiting with return value 1
$ sudo cat x-0.log
X: cannot stat /etc/X11/X (No such file or directory), aborting.
答案1
尝试按CTRL+ ALT+F1然后：
sudo /etc/init.d/gdm stop (for Gnome)
sudo /etc/init.d/lightdm stop (for Unity)
sudo dpkg-reconfigure xserver-xorg
如果您希望备份，X那么不用担心：
sudo cp /etc/X11/xorg.conf /etc/X11/xorg.conf.backup
完成所有这一切后，开始X显示：
sudo /etc/init.d/gdm start (for Gnome)
sudo /etc/init.d/lightdm start (for Unity)