Configuring the Display Manager The following is a partial list of the files, terms, and utilities used

X Windows

Configuring the Display Manager


The following is a partial list of the files, terms, and utilities used:


• lightdm

   The LightDM display manager



•/etc/lightdm/


  The LightDM display manager is configured using several different files:


     • /usr/share/lightdm/lightdm.conf.d
     • /etc/lightdm/lightdm.conf.d
     • /etc/lightdm/lightdm.conf






LX0-104 Exam Objectives (I)

X Windows: Configuring the Display Manager

X Windows

Configuring the Display Manager

You can configure your display manager by editing the appropriate
configuration file:



• xdm /etc/X11/xdm/xdm-config

• LightDM The LightDM display manager is configured using several
different files:

    • /usr/share/lightdm/lightdm.conf.d 
    • /etc/lightdm/lightdm.conf.d
    • /etc/lightdm/lightdm.conf


    • kdm The KDE display manager is actually based on xdm and usually
      uses the xdm configuration files. However, some distributions store
      your kdm settings in /etc/kde/kdm or /etc/X11/ kdm instead. In this
      situation, you will use the kdmrc file in either of these directories
      to make most configuration changes.


    • gdm /etc/X11/gdm



We are going to focus on configuring the LightDM display manager in
this chapter.


When working with the LightDM display manager, it’s important to
remember that all of its configuration files are combined together to
configure LightDM. The key is the fact the files are applied in the
order shown previously.


The default LightDM configuration is stored in the configuration files in


/usr/share/lightdm /lightdm.conf.d/



These files are generated by the system and should not be edited directly. 


Instead, you should create override files containing the changes you want to make in


/etc/lightdm /lightdm.conf.d/


(Alternatively, you can also enter them into the 

/etc/lightdm/lightdm.conf file.)


If there are identical settings in more than one file, the setting in the last file processed
is applied and the others are overridden. For example, suppose you
wanted to override the default session type (configured in
/usr/share/lightdm/lightdm.conf.d/50-ubuntu.conf); you could make a
file named /etc/lightdm/lightdm.conf.d/50-myconfig.conf and enter the
appropriate configuration settings.



LightDM uses the concept of a greeter, which is basically a user
interface for interacting with LightDM. For example, the Ubuntu
distribution uses the Unity greeter by default. You can customize the
way LightDM works and which greeter it uses using the LightDM
configuration files, including the following:


You can change which greeter LightDM uses. To do this, create the
appropriate file in

/etc/lightdm/lightdm.conf.d/ 

and specify the name of a greeter file (which has a .desktop extension) that you want to
use in

/usr/share/xgreeters 

Use the following syntax:

[SeatDefaults]
     greeter-session=file_name


You can disable guest logins. By default, LightDM allows you to log in
to the system as a guest user. For security reasons, you may want to
disable this functionality. To do this, create the appropriate file in


/etc/lightdm/lightdm.conf.d/ 

and enter the following lines:

[SeatDefaults]
     allow-guest=false


You can hide the user list. Many LightDM greeters display a list of
possible user accounts by default. Again, for security reasons, you
may want to disable this functionality. Create the appropriate file in


/etc/lightdm/lightdm.conf.d/ 

and enter the following lines:

[SeatDefaults]
     greeter-hide-users=true


You can configure LightDM to allow manual logins. By default, the
Unity greeter doesn’t allow you to manually enter a username when
logging in to the system. You can reconfigure Unity to allow this by
creating the appropriate file in 

/etc/lightdm/lightdm.conf.d/ 


and enter the following lines:


     [SeatDefaults]
      greeter-show-manual-login=true


You can change the default session type used by LightDM by manually
specifying a session file. 

These files have a .desktop extension and are located in 

/usr/share/xsessions. 

Again, create the appropriate file in 

/etc/lightdm/lightdm.conf.d/ 

and enter the following lines:


     [SeatDefaults]
     user-session=file_name







LX0-104 Exam Objectives (I)

X Windows: Configure the display manager load at start up

X Windows

Configure the display manager load at start up

Because the display manager is managed using an init script, you can
control whether or not the display manager is loaded when the system
boots using the chkconfig command.

For example, to configure the xdm
display manager to not load at boot, enter

 chkconfig xdm off.

You can verify that it is disabled by entering

chkconfig xdm –l

at the shell prompt. Here is an example:



ws1:/ # chkconfig xdm off

ws1:/ # chkconfig xdm –l

xdm                       0:off  1:off  2:off  3:off  4:off  5:off  6:off



Alternatively, to configure the display to automatically load at
system start, you would enter

chkconfig xdm on. 


Again, enter

chkconfig xdm –l 


to verify that the display manager is configured to start
automatically at runlevel 5, as shown here:




ws1:/ # chkconfig xdm on

ws1:/ # chkconfig xdm –l

xdm                       0:off  1:off  2:off  3:off  4:off  5:on   6:off







LX0-104 Exam Objectives (I)

X Windows: enable or disable the display manager

X Windows

Enabling or Disabling the Display Manager

You can enable or disable the display manager using an init script.


Which one depends on the Linux distribution you’re using. On many
Linux distributions, such as openSUSE, the display manager is
managed by the xdm init script located in the /etc/init.d directory.


Other distributions may use the GNOME display manager (gdm) or the KDE
display manager (kdm). To manually manage the display manager, enter


/etc/init.d/init_script stop or start 


at the shell prompt.


You can also use rcxdm stop or start to accomplish the same thing.





LX0-104 Exam Objectives (I)