106.2. Setup a display manager
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Description: Candidates should be able to describe the basic features and configuration of the LightDM display manager. This objective covers awareness of the display managers XDM (X Display Manger), GDM (Gnome Display Manager) and KDM (KDE Display Manager).
Key Knowledge Areas:
Basic configuration of LightDM
Turn the display manager on or off
Change the display manager greeting
Awareness of XDM, KDM and GDM
Terms and Utilities:
lightdm
/etc/lightdm/
A Linux desktop environment is a collection of applications designed to work well with each other and provide a consistent user experience. A desktop environment is usually paired with a login manager. The login manager also known as a greeter or display manager
What is Display Manager ?
The display manager is a bit of code that provides the GUI login screen for your Linux desktop. After you log in to a GUI desktop, the display manager turns control over to the window manager.
Kernel -> X -> DisplayManager -> Desktop
When you log out of the desktop, the display manager is given control again to display the login screen and wait for another login.
There are several display managers—some are provided with their respective desktops while some others not.
Any of the display managers can be used for your login screen regardless of which desktop you are using. Such is the flexibility of Linux and well-written, modular code.
to get the default display manager you can try :
LightDM
LightDM is a free and open-source X display manager that aims to be lightweight, fast, extensible and multi-desktop.
LightDM is the display manager running in Ubuntu up to version 16.04 LTS. While it has been replaced by GDM in later Ubuntu releases
/etc/lightdm
LightDM configuration is located in /etc/lightdm directory:
lets see some confiurations inside /etc/lightdm/lightdm.conf :
In some distributions (ubuntu )configuration files are located inside lightdm.conf.d directory:
changing greeter session:
For instance lets install another greeter session for lightdm and test it
next we need to edit lightdm.conf and change line bellow:
restart lightdm using systemctl restart lightdm
and see the result:
Controlling Display managers
Installing and switching between different Display Managers is pretty easy , as we have seen in CentOS, we can install new DM via yum /apt
commands. Next some modifications in configuration files might be needed example /etc/lightdm/lightdm.conf
.And finally we should enable previous DM and enable the new one with systemctl enable/disable lightdm
commands and reboot
.
For disabling Display Manager ang going to text mode it depends on your distribution! We can either use telinit
command or set default target via systemctl set-default
command.
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https://developer.ibm.com/tutorials/l-lpic1-106-2/
https://opensource.com/article/16/12/yearbook-best-couple-2016-display-manager-and-window-manager
https://en.wikipedia.org/wiki/LightDM
https://wiki.ubuntu.com/LightDM
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