LightDM has recently exploded onto the Linux scene as it was chosen to replace GDM in the release of Ubuntu 11.10. This display manager is not much different from GDM, the code has simply been optimised thoroughly.
More About LightDM
This display manager will function well with most popular desktop environments. Expect faster loading times with this login manager due to the better code base as well.
Remote Logins Supported
Like other popular display managers there is also support for remote logins using XDMCP.
Ubuntu users can install this display manager using the commands seen below, if by chance it is missing.
First you can add the personal package archive to your sources using the next command.
$ sudo apt-add-repository ppa:lightdm-team/ppa
Now you can begin installing this high quality display manager with the following command.
$ sudo apt-get install lightdm lightdm-greeter-example-gtk
First I will take a look at some of the basic functions of LightDM and the display manager in general.
The display manager is started automatically when you boot your computer, that is if it installed and configured correctly. The display manager then loads a greeter screen that you can use to authenticate system users. From the greeter screen you can also choose many other options, like which desktop environment or window manager you wish to load, or you can choose which language you want to use for the greeter screen.
Other LightDM Functions
The display manager also has several other functions, it is used to launch X sessions, the greeter, and user sessions. It handles user authentication, user switching, and much more.
If you want to customize this display manager you can manually using the configuration files, or you can use a simple graphical user interface that can be installed separately. This tool was suggested by UbuntuGeek.com, you can find a link near the bottom.
Simple LightDM Manager
To install this convenient tool just use the commands listed below, unfortunately only a few options are provided. First add the PPA to your sources list.
$ sudo apt-add-repository ppa:claudiocn/slm
Next you will need to update your sources before you can finish installing the application.
$ sudo apt-get update
Installing Simple LightDM Manager
When that is finished simply begin the installation with the commands below.
$ sudo apt-get install simple-lightdm-manager
Users can customize the greeter background manually by changing a single variable in a single file, not so hard. First open the file seen below, then edit the backgrounds variable which I will explain after.
To use a background image just change the backgrounds variable to point to a new image file, there is an example below.
To use a background color for the greeter screen you can just change the background variable to a he
You can customize and interact with this login manager from the command line with the commands and options below.
$ lightdm --option
In many cases there are also short options available as seen below.
$ lightdm -o
Other Useful Options
This will display debug information for LightDM.
$ lightdm --debug
The help option will display a short explanation of how do use LightDM from the command line.
$ lightdm --help
With the following option you can run the display manager as a user and disregard anything that requires root access. This is useful for testing different greeter screens.
$ lightdm --test-mode
If I am not mistaken the following command will allow you to set a new command alias for running your X servers.
$ lightdm --xserver-command=COMMAND
Use this to see current version information for LightDM.
$ lightdm --version
LightDM Display Options
The next command will let you set a new virtual display size for your X servers.
$ lightdm --minimum-vt=NuMBER
Use the next command to set the number of displays to use for your X servers.
$ lightdm --minimum-display-number=NUMBER
Here are a few of the important configuration files for this display manager. First is your common configuration file.
Next is your user list configuration file.
The last configuration file is for your XDMCP keys.
Changing Important Files LightDM
You can use the command below to set a new configuration file to be used next time you start LightDM.
$ lightdm --config=FILE
Change the directory of your stored cache files with the command below.
$ lightdm --cache-dir=DIRECTORY
This will change the directory used to store your running states.
$ lightdm --run-dir=DIRECTORY
If you want to you can even set a new password file, just use the commands below.
$ lightdm --passwd-file=FILE
Use this to change a new file for writing PID.
$ lightdm --pid-file=FILE
Even change the directory where your log files are stored with this command.
$ lightdm --log-dir=DIRECTORY
This will let you change the directory to load your greeters from.
$ lightdm --xgreeters-dir=DIRECTORY
With the next command you can change the directory that you are loading your X server from.
$ lightdm --xsession-dir=DIRECTORY
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