[rhelv6-list] Gnome - KDE Desktop switching in RHEL6

[Gianluca Cecchi]

On Sat, Feb 8, 2014 at 12:06 AM, Horst Severini wrote:
> Hi all,
>
> we are working on upgrading our desktop cluster from RHEL5 to RHEL6, and we
> think we have a workable solution that involves bringing up the new machines
> with ROCKS 6.1 and the RHEL 6.5 ISO, and then doing some post-config via
> scripts, but when we do that, we only have Gnome available at the login
> screen, and we can't figure out how to make KDE available as well.
>
> We have all the KDE RPMs installed (that I know of), via
>
> yum groupinstall "KDE (K Desktop Environment)"
>
> and I have compared the list of installed RPMs with one RHEL6 test install
> we did manually, and I can't figure out what's missing, since everything
> that looks like it's even remotely related to KDE and desktop switching is
> already installed, so I don't know why the ROCKS installed machines don't
> show the desktop switcher box at the bottom of the login screen.
>
> I tried googling around, but haven't quite found the right page yet.
> What are we missing?


What worked for me on a CentOS 6.5 install where I had only Gnome and
init level was 5 by default:

sudo yum groupinstall "KDE Desktop"

verify you have kdm executable (in practice the kdm rpm package)
vi /etc/sysconfig/desktop (is not present by default)

put into it the single line
DISPLAYMANAGER=KDE

$ sudo init 3
$ sudo init 5

and I get kde diplay manager.

take into account that display manager in 6.5 is managed by upstart
init script prefdm.conf in /etc/init directory

and at the end it runs
exec /etc/X11/prefdm -nodaemon

and prefdm contains:

if [ -f /etc/sysconfig/desktop ]; then
        . /etc/sysconfig/desktop
        if [ "$DISPLAYMANAGER" = GNOME ]; then
                preferred=/usr/sbin/gdm
                quit_arg="--retain-splash"
        elif [ "$DISPLAYMANAGER" = KDE ]; then
                preferred=/usr/bin/kdm
....

Otherwise some lines below it contains:
# Fallbacks, in order
exec gdm "$@" >/dev/null 2>&1 </dev/null
exec kdm "$@" >/dev/null 2>&1 </dev/null

so you can comment out the one starting with gdm and it will start kdm
if it finds it...

If you like a display manager not managed by prefdm you have to create
a prefdm.override in /etc/init and put there your display manager
commands/options

HIH,
Gianluca