Problems with LightDM on linux-lts

bope · 2026-10-12 20:40:24

Hi. I'm very desperate. I have tried everything I could before asking here....
So, I have a Dell XPS laptop from 2019. It's integrated card is Intel i915 and it has a dedicated Nvidia card (1650). I also have an external monitor connected via hdmi port.
Currently I use XFCE4, an old 6.0.12 kernel and recently I've decided to install linux-lts kernel as well. Version 6.18.55.
Alas, when I installed that LTS kernel, re-generated the image and tried booting my system with that new Kernel it simply gets stuck before showing my LightDM.

Symptoms when booting LTS kernel (without "quiet" option):
1) Normal boot messages are being printed (I use systemd ofc)
2) My external monitor activates mirroring content of my laptop monitor
3) After what feels like almost end of the boot process I get a message "Started LightDm"
4) Laptop freezes up and CPU fans soon speeds up as if CPU is very active
5) I can't switch to tty2 and have to manually reboot my system.

I tried disabling LighDM and installing/using Slim and SDDM - same result.

Facts:
1) I don't have /etc/X11/xorg.conf file
2) I don't have any Nvidia drivers installed as I don't use my Nvidia card actively, I don't need them.
3) My Nouveau driver is blacklisted
4) I don't have any custom Intel config inside /etc/X11/xorg.d/
5) On 6.0.12 kernel everything runs perfectly
6) I have latest linux-firmware and linux-firmware-whence installed (but even with previous versions from 2024 the problem was the same).
7) My mkinitcpio has only module "i915" included and as for the HOOKS I have: base systemd autodetect microcode modconf kms keyboard keymap consolefont sd-vconsole block filesystems fsck
8) My LightDM config is (but this apparently is not related to LightDm itself):

[Seat:*]
A  greeter-wrapper=/etc/lightdm/Xgreeter
B  type=local
B  pam-service=lightdm
B  pam-autologin-service=lightdm-autologin
B  pam-greeter-service=lightdm-greeter
B  greeter-session=lightdm-slick-greeter
B  user-session=xfce
B  session-wrapper=/etc/lightdm/Xsession
B  autologin-user=boza

   [LightDM]
B  run-directory=/run/lightdm

Sources:
A  /etc/xdg/lightdm/lightdm.conf.d/90-greeter-wrapper.conf
B  /etc/lightdm/lightdm.conf

Interesting thing: when I disable LightDM and boot using LTS kernel I get a bash login prompt and after logging in when I type "startx" my desktop starts up normally! Also, when from that desktop I click on "Logout" or "Switch user" button, both screens go blank and laptop is frozen again. Also, same thing happens if I start LightDm from the console, before trying "startx".
I checked both X logs and LightDM logs and couldn't find any error report.

I'm simply out of ideas....

seth · Yesterday 06:44:06

LightDM is configured to autologin you into xfce, what happens if you disable that?
Does startx start xfce as well or just TWM/xterm/xclock?

I checked both X logs and LightDM logs and couldn't find any error report.

Make sure you were not looking at the Xorg log from the running server (in doubt archive it before running startx) and post both along the system journal for the failing boot, eg.

sudo journalctl -b -1 | nc termbin.com 9999

for the previous one

2) I don't have any Nvidia drivers installed as I don't use my Nvidia card actively, I don't need them.
3) My Nouveau driver is blacklisted

This is not a very good idea as it will result in nothing controlling the chip - disable it in the UEFI settings if you don't want to use it at all.

bope · Yesterday 22:24:22

Ok, so I tried disabling this LightDm option
autologin-user
but no luck.

When I disable LightDm altogether and login to bash, then startx my fully functional desktop appears. Ok, browser (Brave) password storage is locked but desktop works....

Regarding journal logs hmmmm not sure how to preserve them. That's the issue. Because when i try booting the 6.18 kernel with LightDM enabled, whole laptop together with screen just freezes.... When i reboot to 6.0.12 to disable and then again to 6.18 logs are gone :\

seth · Today 06:27:57

If you only boot the multi-user.target and instead of running startx start lightdm from there, does it work?

The journal logs multiple boots and you can also upload logs from the console by netcat'ing them into termbin like illustrated in #2
(Make sure this is immediately after a failed boot)

bope · Today 16:49:55

seth wrote:

If you only boot the multi-user.target and instead of running startx start lightdm from there, does it work?

I forgot to specify that in my original post. I also tried exactly that. Booted into level 3, everything works, as soon as I tried starting LightDm via systemctl result was the same. Screen stuck, CPU fan ramps up after few seconds, I have to manually reboot.

What I did now according to your instructions:

1) Booted 6.18 without "quiet" option and let the laptop get stuck
2) Manually rebooted
3) Booted 6.18 to level 3, logged in
4) Immediately executed your journal command (nice tool that "termbin", had no idea about it!)

This is the result: https://termbin.com/eumb3
Seems like this log is the one during the failed boot judging by boot image params (no "quiet" and now "3").

Last edited by bope (Today 17:31:54)

seth · Today 17:53:46

The journal never reaches graphical target and there's no login - did you "manually" reboot w/ the power button?
Don't. Try https://wiki.archlinux.org/title/Keyboa … el_(SysRq) + REISUB to get the journal synced to disk - also xorg log and lightdm log would certainly be interesting.

pci=noaer

Why is that there?
nb. that it will not "fix" anything but only suppress (pot. crucial) error messages.

From what else is there, try to remove the logitech dongle, https://bbs.archlinux.org/viewtopic.php?id=315169

bope · Today 20:11:02

seth wrote:

Why is that there?

I think it's a legacy option. I'm using this same system pretty much since 2012.

Anyway I tried again. What I did:

1) From working kernel made sure

cat /proc/sys/kernel/sysrq

is 1

2) Removed all my USB devices
3) Booted LTS without "pci=noaer"
4) Got stuck again
5) Tried Alt+SysReq+s and Alt=SysReq+b few seconds apart => nothing happened
6) Manually rebooted

7) Rebooted back to lts to level 3
8) Checked xorg log => file exists with correct time that corresponds last failed boot but it's empty
9) Checked journal for last boot: similar thing to what I have on pastebin, no errors in the end
10) Checked last lightdm log: file exists with correct time but size is 0 just like with Xorg log
11) To confirm SysReq works I rebooted using Alt+SysReq+b

bope · Today 20:26:57

Update. Now I did this as a sanity check:

1) Compiled a custom Kernel from 7.2.9. I've removed debugging and some device drivers I won't need to speed up the compilation
2) Installed and and tried everything with it - same result. So, it's not related strictly to 6.18.

I also remembered something! 4 days ago, while investigating this issue and trying to see why laptop is stuck, I was suddenly presented with a Kernel panic message! I managed to make a photo. Not sure if it's helpful, I couldn't get any info from it.
https://ibb.co/BVL8cn9f

seth · Today 20:28:07

5) Tried Alt+SysReq+s and Alt=SysReq+b few seconds apart => nothing happened

That would suggest the kernel halted… https://wiki.archlinux.org/title/Kdump

Before that:

B  greeter-session=lightdm-slick-greeterB  greeter-session=lightdm-slick-greeter

Do you get the same w/ https://archlinux.org/packages/extra/x8 … k-greeter/ ?

4) I don't have any custom Intel config inside /etc/X11/xorg.d/

Do you have xf86-video-intel *installed*?
Don't. This will lead to a broken GL stack (among other things)

In doubt also post a "good" xorg log for an oversight.

Edit: the panic fits the lightdm behavior but the screenshot doesn't hint at any direct causes (other than the MCE which can have all sorts of reasons, possibly see https://wiki.archlinux.org/title/Intel_ … Intel_CPUs

Last edited by seth (Today 20:35:08)

bope · Today 21:13:23

Ok, i tried with lightdm-gtk-greeter: same result.

I don't have xf86-video-intel installed (even thou I have some other xf86 stuff like xf86-video-vesa and xf86-video-fbdev.

"Good" logs:
Xorg: https://termbin.com/w68p
Lightdm: https://termbin.com/4hj5p
X-0.log (Lightdm): https://termbin.com/uplyk

Arch Linux

#1 2026-10-12 20:40:24

Problems with LightDM on linux-lts

#2 Yesterday 06:44:06

Re: Problems with LightDM on linux-lts

#3 Yesterday 22:24:22

Re: Problems with LightDM on linux-lts

#4 Today 06:27:57

Re: Problems with LightDM on linux-lts

#5 Today 16:49:55

Re: Problems with LightDM on linux-lts

#6 Today 17:53:46

Re: Problems with LightDM on linux-lts

#7 Today 20:11:02

Re: Problems with LightDM on linux-lts

#8 Today 20:26:57

Re: Problems with LightDM on linux-lts

#9 Today 20:28:07

Re: Problems with LightDM on linux-lts

#10 Today 21:13:23

Re: Problems with LightDM on linux-lts

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