Graphic login managers

My opensuse install includes several graphic login managers, so I decided to try them all out.  This post will report my experience with them.  In particular, I will be discussing:

  • kdm – this is installed as part of the KDE pattern;
  • gdm – this is installed when you install Gnome;
  • lightdm – this appears to come with XFCE;
  • lxdm – the login manager for LXDE
  • xdm – a standard and tradition part of a basic Xwindows install.

During testing of 13.1 pre-release versions, I also installed enlightenment.  Apparently, that comes with “entrance” as a login manager.  But I do not currently have that installed, so I did not test it.  My experience with enlightenment was unenlightening.

Which to use is selected by the script “/etc/sysconfig/displaymanager”.  An easy way to edit that, is to use:

Yast –> /etc/sysconfig editor –> Desktop –> Display manager

and edit the variable “DISPLAYMANAGER”.  The change will probably take place at the next reboot.  If you want to hurry things up, then get to a virtual tty with CTRL-ALT-F1, login as root, and use

telinit 3  ## switch to init level 3
telinit 5  ## switch back to init level 5

This switches to the newly defined DISPLAYMANAGER without rebooting.

kdm

If you have installed KDE as your default desktop, then “kdm” will probably be the login manager you are using.  It is simple and elegant, at least with the current opensuse artwork.  All else being equal, this would be my preferred login GUI.  However, all else is never equal, so at present I am using “lightdm” on my main systems.

The display lists all users, and preselects the most recently logged in user.  The tool icon can be used to select which login session (KDE, Gnome, etc).  There’s also an on/off icon you can use to shutdown or reboot the system.

Among the desktop sessions you can choose, there is one for “failsafe”.  This gives a very simple “twm” session with just one xterm window.  When you exit from that xterm, the session terminates.  This is occasionally useful when you want to be logged in for repairs, but without the full overhead of a normal desktop.  None of the other GUI login managers offers the failsafe session.

“kdm” also offers a failsafe KDE session.  I have not been able to see any difference between this and a normal KDE session.  If the Gnome classic extensions are installed, “kdm” offers Gnome classic as a login option.  However, it appears to not work.  You get only ordinary Gnome 3, without the classic extensions being loaded.

When using “kdm” to login to Gnome, you will find that the Gnome keyring has not been opened.  That’s the main disadvantage to “kdm”, and is one of the reasons why I am currently using “lightdm”.

According to a recent KDE commit digest, “kdm” is being removed from KDE.  Reports suggest that it may be replaced by “sddm” which is not in the standard opensuse repos.  I do not know whether opensuse will continue to use “kdm”.

gdm

If you installed Gnome as your default desktop, then you probably have “gdm” as your login manager.  If you login to Gnome or XFCE using “gdm”, then it does unlock the Gnome keyring.  It does not unlock it for an LXDE login.  If you have installed the Gnome classic extensions, then there should be a selection to login to Gnome Classic.  And this does work with “gdm”, but does not seem to work with other login managers.  Unfortunately, if you login to Gnome classic, the Gnome keyring is not unlocked.  I’m guessing that’s a bug, but not one for me to pursue since I don’t much like either Gnome or Gnome classic.

In truth, I don’t much care for “gdm”.  It has a fairly simple display, yet insists on making heavy use of graphic acceleration.  This is perhaps why it is slower to startup than “kdm”.  Its accelerated graphics are working fine with Intel graphics, or with the nvidia drivers for an nvidia card.  The display is sometimes messed up with the nouveau driver and an nvidia card.  When I last tried “gdm” on an older (2004 vintage) system with radeon graphics, “gdm” went into an apparent loop and never finished starting.  I had to kill the X-session to recover.  That was with one of the 13.1 milestone releases.  I have not since tried “gdm” on that box.

lightdm

If you installed XFCE, then you probably have “lightdm” on your system and it might even be the default login manager.  It’s display is relatively simple, but not as elegant as that of “kdm”.  Perhaps that’s just a matter of the artwork.  One thing that I really like about “lightdm”, is that it tells you on the login screen, which desktop you will be logged into.  You can, of course, change that.  With both “kdm” and “gdm” you have to select the option to see how your login will default.  With “lightdm” it is right there on the screen.  As with both “kdm” and “gdm”, it does remember your most recent login, and default to the same desktop.

When using “lightdm”, the Gnome keyring is unlocked for a login to either Gnome or to XFCE.  There is a menu choice for “Gnome Classic” (assuming that you have installed the classic extension).  However, it does not work.  It just logs you into standard Gnome 3, but without the Gnome keyring being unlocked.

There is an outstanding bug for “lightdm”.  This is Bug 846832.  With this bug, after reboot, “lightdm” sometimes fails to start.  Instead you get a command line screen.  There, you can login as root, switch to init level 3, then switch back to init level 5 to get it to start.  The bug reports suggest that this may only happen with Intel graphics.  I have only noticed it with a 32-bit install using Intel graphics.  I have not had any such problem with my 64-bit installs, nor with 32-bit install and nvidia graphics.

My current preference is for “lightdm”.  That’s because it does unlock the Gnome keyring for both Gnome and XFCE logins, and — more importantly — because it displays the default session on the login screen.

lxdm

If you have installed LXDE, then you probably have “lxdm” installed.  And perhaps it is your default login manager.

The “lxdm” display is simple.  However, once you select a user, you cannot change your mind.  It switches the screen to a box for password.

Of the several display managers tested, “lxdm” appears to be the only one that unlocks the Gnome keyring for an LXDE session.  It does not unlock the keyring if you choose a Gnome or XFCE session.  If you mainly login to LXDE, this might be a good reason for preferring “lxdm”.

xdm

The “xdm” login manager is very simple — perhaps “barebones” would be a better description.  It provides a way of providing the user and password, but nothing more.  On my system, it will only log me into KDE.

Traditionally, “xdm” is the login manager for X.  I used to use it when I started with linux, almost 20 years ago.  I would define my login session in “.xsession” in my home directory.  If there is no “.xsession”, then a system-wide default is used.  I presume that this still works, though I have not tested it.  That is to say, I could probable define my session the way that I want it in “.xsession”, instead of it defaulting to KDE.  Some users might like the versatility that this provides, while others will prefer the menu selection of desktops available with other login managers.

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About Neil Rickert

Mathematician and computer scientist who dabbles in cognitive science.

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