Switch from gdm3 to lightdm in noninteractive mode.

[randy11@free.fr]

Hello,

I must switch from 'gdm3' to 'ligthdm' in a non
interactive mode. I must make the switch in the
'preseed' file used to install the PC with PXE.

I've tried without success :

echo "lightdm shared/default-x-display-manager select lightdm" | debconf-set-selections
echo "gdm3 shared/default-x-display-manager select lightdm" | debconf-set-selections
echo "sddm shared/default-x-display-manager select lightdm" | debconf-set-selections

debconf-get-selections | grep lightdm
 lightdm lightdm/daemon_name string  /usr/sbin/lightdm
 # Choices: gdm3, gmd3, lightdm, sddm
 gdm3  shared/default-x-display-manager  select  lightdm
 gmd3  shared/default-x-display-manager  select  lightdm
 lightdm shared/default-x-display-manager  select  lightdm
 sddm  shared/default-x-display-manager  select  lightdm

dpkg-reconfigure --frontend=noninteractive lightdm

cat /etc/X11/default-display-manager
 /usr/sbin/gdm3

The content of of '/etc/X11/defautl-display-manger'
is changed only in manual mode with the regular :
dpkg-reconfigure ligthdm

Any help will be appreciate.

Best regards.

Randy11.