What is gdm in linux

gdm(1) — Linux man page

GDM is a replacement for XDM, the X Display Manager. Unlike its competitors (X3DM, KDM, WDM) GDM was written from scratch and does not contain any original XDM / X Consortium code. GDM runs and manages the X servers for both local and remote logins (using XDMCP). See http://www.gnome.org/projects/gdm/ for more details.

gdm is just a script that runs the actual gdm-binary executable. gdm-stop is a script that stops the current running daemon immediately, gdm-restart restarts the current daemon immediately and gdm-safe-restart restarts the current daemon after everyone has logged out. gdmsetup is a graphical tool for easily changing the most commonly used options.

For full documentation see the GNOME help browser under the GNOME / System section.

Options

gdm and thus also gdm-binary accept the following options: -nodaemon Do not fork into the background —no-console No console (local) servers to be run —preserve-ld-vars Preserve LD_* variables —version Print the GDM version —help Print simple description of accepted options

gdmsetup accepts all standard GNOME options.

Configuration

Configuration is done either by running gdmsetup or by editting the /etc/X11/gdm/gdm.conf (usually, could also be /etc/gdm/gdm.conf) file. The graphical tool does not support all the options possible so editting the configuration file is sometimes necessary.

Author

GDM is being written and maintained by George (Jiri) Lebl based on the original codebase by Martin K. Peterson .

Источник

What is LightDM and GDM

What is LightDM and GDM? In Linux operating system I heard both but I don’t know about them and what is called? Where they are used? Are they related to display?

1 Answer 1

LightDM is an x display manager that aims to be lightweight, fast, extensible and multi-desktop. It uses various front-ends to draw login interfaces, so-called Greeters.

• A well-defined greeter API allowing multiple GUIs
• Support for all display manager use cases, with plugins where appropriate
• Low code complexity
• Fast performance

LightDM offers at least the same functionality as GDM but it has a simpler code base and does not load any GNOME libraries to work. LightDM is the default display manager for Ubuntu.

LighDM configuration is governed by the configuration files in /etc/lightdm/lightdm.conf.d/ . To add your own configuration, create a new file in that directory such as /etc/lightdm/lightdm.conf.d/my.conf .

GDM (the GNOME Display Manager) is a display manager (a graphical login program) for the windowing systems X11 and Wayland.It is a highly configurable reimplementation of xdm, the X Display Manager.

Gdm allows you to log into your system with the X Window System running and supports running several different X sessions on your local machine at the same time.

The X Window System by default uses the XDM display manager. However, resolving XDM configuration issues typically involves editing a configuration file. GDM allows users to customize or troubleshoot settings without having to resort to a command line.

Источник

What is gdm in linux

GDM is the GNOME Display Manager, a graphical login program that uses Wayland or the X Window System.

• it pre-loads the X Window System (though this can be a disadvantage for servers)
• users can select various desktop environments and windows managers on a per-login basis
• assistance for users with disabilities
• per-login regional settings and keyboard layout
• consistent look and feel of other GTK/GNOME-themed applications
• all other functionalities of XDM, including XDMCP support for managing remote displays

By default, the greeter is run as an unprivileged user and logging in as root is forbidden.

Controlling the GDM daemon

GDM is a service that can, like all other services in your system, be controlled with the systemctl command.

To set your system to always boot to a console rather than GDM:

$ systemctl set-default multi-user.target

To revert the previous command and have your system always boot straight into GDM:

$ systemctl set-default graphical.target

To check the current boot target:

Configuration

Disabling Wayland

In Debian 10 and newer, GDM will use Wayland by default on supported hardware. This can be overridden in the /etc/gdm3/daemon.conf file by uncommenting the WaylandEnable=false line, forcing it to instead use X11.

Customizing the GDM appearance

1. Edit /etc/gdm3/greeter.dconf-defaults as root
2. Uncomment and/or modify the desired settings
3. Save and close the editor
4. Finally, run as root: dpkg-reconfigure gdm3

The command ‘dpkg-reconfigure gdm3‘ will cause gdm to reload its configuration upon the next logout or reboot.

Note: When changing the background image, the target file must be world-readable.

Removing autologin in gdm3 and getting more verbose output in GDM

This is with respect to GDM3 as it’s known in GNOME 3 and above.

$ dpkg -S /etc/gdm3/daemon.conf gdm3: /etc/gdm3/daemon.conf

This is just to have an idea of the ownership of the file.

Now the file would look something like this :-

$ cat /etc/gdm3/daemon.conf # GDM configuration storage # # See /usr/share/gdm/gdm.schemas for a list of available options. [daemon] # Enabling automatic login AutomaticLoginEnable=true AutomaticLogin=$USERNAME # Enabling timed login # TimedLoginEnable = true # TimedLogin = user1 # TimedLoginDelay = 10 # Reserving more VTs for test consoles (default is 7) # FirstVT = 9 [security] [xdmcp] [greeter] # Only include selected logins in the greeter # IncludeAll = false # Include = user1,user2 [chooser] [debug] # More verbose logs # Additionally lets the X server dump core if it crashes Enable = false

Now at times if you remove the user you just cannot go into the DE esp. if only a user is automatically logged in. This is and should be a bug but that’s another tale. Anyways the way to fix it is simple.

$ cat /etc/gdm3/daemon.conf # GDM configuration storage # # See /usr/share/gdm/gdm.schemas for a list of available options. [daemon] # Enabling automatic login AutomaticLoginEnable=false # Enabling timed login # TimedLoginEnable = true # TimedLogin = user1 # TimedLoginDelay = 10 # Reserving more VTs for test consoles (default is 7) # FirstVT = 9 [security] [xdmcp] [greeter] # Only include selected logins in the greeter # IncludeAll = false # Include = user1,user2 [chooser] [debug] # More verbose logs # Additionally lets the X server dump core if it crashes Enable = true

I just added the bits which should help us in case anything does go wrong.

See also

Источник

What is gdm3, kdm, lightdm? How to install and remove them?

What is gdm3, kdm, lightdm? How to install and remove and repair them? Can anyone explain in details?

5 Answers 5

gdm3 , kdm , and lightdm are all display managers. They provide graphical logins and handle user authentication.

A display manager presents the user with a login screen. A session starts when a user successfully enters a valid combination of username and password.

GNOME Display Manager ( gdm3 )

gdm3 is the successor of gdm which was the GNOME display manager. The newer gdm3 uses a minimal version of gnome-shell , and provides the same look and feel of as GNOME3 session. Is the Canonical choice since Ubuntu 17.10. You can install it with:

KDE Display Manager ( kdm )

kdm was KDE’s display manager. But it’s been deprecated in KDE5 in favor of SDDM , which is more capable as a display manager, and hence comes by default with Kubuntu. You can install it with:

LightDM

LightDM was Canonical’s solution for a display manager. It was supposed to be lightweight and comes by default with Ubuntu (until 17.04), Xubuntu, and Lubuntu. It’s configurable, with various greeter themes available.

sudo apt-get install lightdm 

sudo apt-get remove lightdm 

Repairing is broad term. However, if you have multiple display managers installed, you can choose between them using:

sudo dpkg-reconfigure gdm3 

You can use any display manager’s name in place of gdm3 in the above command, and it will allow you to choose between them. You must reboot for the change to take affect.

To check which display manager is currently being used, run this command:

cat /etc/X11/default-display-manager 

One important point to note that, currently due to a bug (I checked in 16.04) you cannot start GNOME3 or Ubuntu Unity session using SDDM. So, if you have both KDE and Unity or GNOME3 installed, make sure your display manager is either gdm3 or lightdm .

Источник