一般是 gdm3 lxdm lightdm etc
https://wiki.archlinux.org/index.php/LightDM#Installation
https://wiki.manjaro.org/index.php?title=LXDM_Configuration
sudo dpkg-recofigure lightdm。
http://forum.ubuntu.org.cn/viewtopic.php?t=350555
https://wiki.archlinux.org/index.php/Display_manager_(%E7%AE%80%E4%BD%93%E4%B8%AD%E6%96%87)
https://wiki.debian.org/GDM
LXDM is a GUI application for the Lightweight X11 Desktop Environment (LXDE).
原来没有
http://unix.stackexchange.com/questions/48450/how-to-install-lxdm-instead-of-gdm3
