/var/log/Xorg.0.log

In my case there were some xserver-xorg-video-* packages missing (fbdev and vesa in my case)

update-rc.d <service> defaults only sets the defaults if there are no symlinks at all. This is so that maintainer scripts can safely run this command on each installation or upgrade without overriding existing user preferences.

If you want to re-assert the defaults or set them after changing the LSB headers, you first need to remove the symlinks. You can therefore do the following:

update-rc.d -f lightdm remove
update-rc.d lightdm defaults

Hope this helps!

(Technically you don't need the -f right now but would do if https://bugs.debian.org/680293 got fixed. You'd like to think the defaults operation accepted -f, wouldn't you? That would be neat!)

sysv-rc-conf

to check on services. That may give you another view of things at least.

#! /bin/sh
### BEGIN INIT INFO
# Provides:          lightdm
# Should-Start:      console-screen kbd acpid dbus hal consolekit
# Required-Start:    $local_fs $remote_fs x11-common
# Required-Stop:     $local_fs $remote_fs
# Default-Start:     2 3 4 5
# Default-Stop:      0 1 6
# Short-Description: Light Display Manager
# Description:       Debian init script for the Light Display Manager

If it does not have the same Default-Start and Default-Stop runlevels, you need to think about when and how that happened. Check to see when the file was last edited. That might give you a clue.

I have no other ideas right now.

Thanks!
I runned "dpkg-reconfigure lightdm". No questions, no problems, no changes, but an interesting side-effect:
The root-user - via ssh - has the wong keyboard, until reboot.

I've already done bevore, what you recommended ("update-rc.d lightdm defaults").
Earlier and now, it gives me:

update-rc.d lightdm defaults
insserv: warning: current start runlevel(s) (empty) of script `lightdm' overrides LSB defaults (2 3 4 5).
insserv: warning: current stop runlevel(s) (0 1 2 3 4 5 6) of script `lightdm' overrides LSB defaults (0 1 6).

I can run startx for user and root, but in both cases, there is no lightdm and no fast userswitching.
If I start lightdm, it works. The use cannot start lightdm, I gave him sudo, then it works.

There is something bad in startup/order. There is no xorg nor lightdm logfile - I deleted them completely
immidiately before reboot.
The bootlog has this interesting part (could post full, but nothing about X/GUI/Lightdm in it), ercerpt:

Starting Setting kernel variables: sysctl.
Starting: AppArmorLoading AppArmor profiles...Skipping profile in /etc/apparmor.d/disable: usr.sbin.squid
done.
.
Configuring network interfaces...if-up.d/mountnfs[eth0]: waiting for interface eth1 before doing NFS mounts ... (warning).
invoke-rc.d: could not determine current runlevel
invoke-rc.d: could not determine current runlevel
invoke-rc.d: could not determine current runlevel
done.
Cleaning up temporary files....
Setting up X socket directories... /tmp/.X11-unix /tmp/.ICE-unix.
Setting sensors limits...No sensors found!

(I dont worry about the lmsensors message, its a (K)VM).

Regards,
Manfred

dpkg-reconfigure lightdm

as root. You'll also see if there's another display manager installed, and it will give you a choice of which one to use.

If it still doesn't work, make sure the lightdm service is set up to run. Either install and run sysv-rc-conf and make sure lightdm is set to run in runlevels 2-5 or run

update-rc.d lightdm defaults

Does startx work for unprivileged user?

I am asking why the gui does not start automatically.
I am using daedalus with sysv-init and lightdm.
As root user I can use "startx &" but I do not see a displaymanager running (at least not lightdm):

$ update-alternatives --get-selections | igrep --color "(light)|(manag)|(display)"
desktop-lightdm-background     auto     /usr/share/images/desktop-base/greeter-sapphire-narrow-large.png
desktop-lightdm-background.xml auto     /usr/share/images/desktop-base/lightdm.xml
lightdm-greeter                auto     /usr/share/xgreeters/lightdm-gtk-greeter.desktop
lightdm-gtk-greeter.conf       manual   /etc/lightdm/lightdm-gtk-greeter.conf-devuan-sapphire
x-session-manager              auto     /usr/bin/startxfce4
x-window-manager               auto     /usr/bin/xfwm4

I have installed lightdm:

apt-cache policy lightdm
lightdm:
  Installed: 1.26.0-8+devuan1
  Candidate: 1.26.0-8+devuan1
  Version table:
 *** 1.26.0-8+devuan1 500
        500 http://deb.devuan.org/merged daedalus/main amd64 Packages
        100 /var/lib/dpkg/status

But:

$ service lightdm status
lightdm is not running ... failed!

and in services:

$ service --status-all | igrep --color "|(disp)|(light)|(sess)|(xorg)|(window)"
 [ ? ]  alsa-utils
.....
 [ - ]  lightdm
.....

I followed the instructions contained in "/etc/init.d/lightdm" and changed it, without success:

# To start lightdm even if it is not the default display manager, change
# HEED_DEFAULT_DISPLAY_MANAGER to "false."
HEED_DEFAULT_DISPLAY_MANAGER="false"

Something should invoke startx at boot, or not?
On my debian desktop (debian 11) lightdm is running.
On both boxes, xfwm4 is the window manager.
Could someone please shed some light onto this?

Using:

Linux host1 6.1.0-28-amd64 #1 SMP PREEMPT_DYNAMIC Debian 6.1.119-1 (2024-11-22) x86_64 GNU/Linux
Devuan GNU/Linux 5 (daedalus)
SysV init version: 3.06

This is a KVM box running devuan with zfs on root
using Virtio display, like lshw shows:

/0/100/2            /dev/fb0   display        Virtio 1.0 GPU

(edited) If I use "startx/startxfce4" from user or root, fast userswitching is not available,
but works, if lightdm has been started manually.

Thanks so far,
Manfred