我有一台延伸显示器连接到我的笔记本电脑。
ArchLinux + systemd + lightdm + lightdm-gtk-greeter。
当我执行reboot或poweroff命令时，2监视器都将显示黑屏（我可以在笔记本电脑屏幕的左上角看到一个光标）。将重新启动，也不会关闭电源。
如果我用ctrl + alt + f1热键切换到控制台tty，然后执行reboot / poweroff命令，那么将正确处理reboot / poweroff操作。
我在/var/log/lightdm/x-0.log中找到了一些错误消息：
[root@XSign hacksign]# cat /var/log/lightdm/x-0.log
X.Org X Server 1.18.3
Release Date: 2016-04-04
X Protocol Version 11, Revision 0
Build Operating System: Linux 4.2.5-1-ARCH x86_64
Current Operating System: Linux XSign 4.5.4-1-ARCH #1 SMP PREEMPT Wed May 11 22:21:28 CEST 2016 x86_64
Kernel command line: initrd=\initramfs-linux.img root=/dev/sda3 rw
Build Date: 05 April 2016 05:24:02PM
Current version of pixman: 0.34.0
Before reporting problems, check http://wiki.x.org
to make sure that you have the latest version.
Markers: (--) probed, (**) from config file, (==) default setting,
(++) from command line, (!!) notice, (II) informational,
(WW) warning, (EE) error, (NI) not implemented, (??) unknown.
(==) Log file: "/var/log/Xorg.0.log", Time: Mon May 30 13:08:38 2016
(==) Using config directory: "/etc/X11/xorg.conf.d"
(==) Using system config directory "/usr/share/X11/xorg.conf.d"
xf86: remove device 0 /sys/devices
任何人都知道如何解决这个问题？