Is LightDM a dependency for Xfce?

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Is LightDM a dependency for Xfce?

Postby Naron » 2018-08-04 11:56

I recently installed Debian 9 on another computer besides my current PC and I have noticed that when I installed Xfce on Debian (apt install xfce4) it also pulled the LightDM and LightLocker packages. I'm pretty sure I have not asked for LightDM to be installed, my login manager of choice was Slim. So, is this normal? I was not aware that LightDM is the official DM for Xfce in Debian. And apparently this has caused some problems with Xfce, more specifically I was asked a few times to provide the root password when I wanted to reboot or shutdown from Xfce. Now I have deleted LightDM and LightLocker and it seems that I can properly reboot or shutdown from Xfce, at least for now.
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Re: Is LightDM a dependency for Xfce?

Postby bw123 » 2018-08-04 12:37

Code: Select all
$ apt -s install xfce4 | grep -B4 light-locker

WARNING: apt does not have a stable CLI interface. Use with caution in scripts.

Recommended packages:
  at-spi2-core libgtk-3-bin libgail-common libgtk2.0-bin notification-daemon
  upower libxfce4util-bin thunar-volman tumbler xdg-user-dirs gvfs xorg
  desktop-base tango-icon-theme xfce4-notifyd pavucontrol dbus-x11
  light-locker
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Re: Is LightDM a dependency for Xfce?

Postby Head_on_a_Stick » 2018-08-04 12:57

Code: Select all
aptitude why light{dm,-locker}
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Re: Is LightDM a dependency for Xfce?

Postby arzgi » 2018-08-04 13:35

Naron wrote:I recently installed Debian 9 on another computer besides my current PC and I have noticed that when I installed Xfce on Debian (apt install xfce4) it also pulled the LightDM and LightLocker packages. I'm pretty sure I have not asked for LightDM to be installed, my login manager of choice was Slim. So, is this normal? I was not aware that LightDM is the official DM for Xfce in Debian. And apparently this has caused some problems with Xfce, more specifically I was asked a few times to provide the root password when I wanted to reboot or shutdown from Xfce. Now I have deleted LightDM and LightLocker and it seems that I can properly reboot or shutdown from Xfce, at least for now.


I too used Slim with xfce, but I don't remember was 9.0 or 8.n, when Slim did not let you login. You can find threads using search.

Also problem logging of xfce has been discussed here.
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Re: Is LightDM a dependency for Xfce?

Postby Head_on_a_Stick » 2018-08-04 17:33

Slim is dead upstream and it doesn't handle systemd login sessions correctly.

For stretch I would recommend either GDM or no display manager at all because those options allow X to be run as the normal user; LightDM runs X as root, which is stupid.
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Re: Is LightDM a dependency for Xfce?

Postby arzgi » 2018-08-05 16:24

Head_on_a_Stick wrote:Slim is dead upstream and it doesn't handle systemd login sessions correctly.

For stretch I would recommend either GDM or no display manager at all because those options allow X to be run as the normal user; LightDM runs X as root, which is stupid.


I purged lightdm, but could not start xfce as user, used startxfce4:
Code: Select all
Fatal server error:
[    37.087] (EE) parse_vt_settings: Cannot open /dev/tty0 (Permission denied)
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Re: Is LightDM a dependency for Xfce?

Postby Head_on_a_Stick » 2018-08-05 19:17

arzgi wrote:used startxfce4

That is the correct command to start the XFCE desktop, not sure why you would have tried anything else :?

It's best to set that as /etc/alternatives/x-session-manager and then use plain old `startx` (with no arguments and no ~/.{xinitrc,xsession}) to bring the GUI up.
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Re: Is LightDM a dependency for Xfce?

Postby arzgi » 2018-08-06 06:54

Head_on_a_Stick wrote:
arzgi wrote:used startxfce4

That is the correct command to start the XFCE desktop, not sure why you would have tried anything else :?

It's best to set that as /etc/alternatives/x-session-manager and then use plain old `startx` (with no arguments and no ~/.{xinitrc,xsession}) to bring the GUI up.


It was so long time, I've last logged in without DM. startx, should had known. /etc/alternatives/x-session-manager was already there, so all I needed was startx.

Thanks Head_on_a_Stick, you seem to know!
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Re: Is LightDM a dependency for Xfce?

Postby Naron » 2018-08-06 10:38

@Head_on_a_Stick: is Slim indeed dead? What a pity, I much prefer it because it's simple and fast. I used LightDM but it was always slow to boot and I had the issue with a gray background being displayed before the Xfce desktop loads - and I really hate that "effect". Your point about running X as user instead as root is interesting (does Slim also run X as root?), but how could I install GDM without pulling a good chunk of the Gnome desktop? I really dislike Gnome, never getting used to it. And I want a graphical login, not startx, simply because I like my login to be this way.
It seems that the problem with shutdown/reboot from Xfce was solved, simply by deleting LightDM and LightLocker.
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Re: Is LightDM a dependency for Xfce?

Postby Head_on_a_Stick » 2018-08-06 10:51

Naron wrote:does Slim also run X as root?

I would imagine so, this might show you:
Code: Select all
ps aux | grep X

Or use htop[1] and check who owns the Xorg process.

how could I install GDM without pulling a good chunk of the Gnome desktop?

I would try
Code: Select all
apt-get install --no-install-recommends gdm3

but you will probably still get a pile of crap pulled in :mrgreen:

[1] Other task managers are available.
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Re: Is LightDM a dependency for Xfce?

Postby CwF » 2018-08-06 21:00

You could try nodm to avoid startx.

https://packages.debian.org/search?keywords=nodm
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Re: Is LightDM a dependency for Xfce?

Postby Head_on_a_Stick » 2018-08-06 21:15

^ You don't need a package for that, see viewtopic.php?f=16&t=123694
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Re: Is LightDM a dependency for Xfce?

Postby wizard10000 » 2018-08-07 11:19

I'm pretty sure Debian doesn't start X as root any more and AFAIK hasn't since 2015. Not at home but will check when I get there :)
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Re: Is LightDM a dependency for Xfce?

Postby Head_on_a_Stick » 2018-08-07 11:33

wizard10000 wrote:Debian doesn't start X as root any more and AFAIK hasn't since 2015

Check the stretch release notes d00d:

https://www.debian.org/releases/stable/ ... uires-root

EDIT: I know from my experience at BunsenLabs that LightDM in stretch runs the Xorg process owned by root.
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Re: Is LightDM a dependency for Xfce?

Postby None1975 » 2018-08-07 13:00

wizard10000 wrote:I'm pretty sure Debian doesn't start X as root any more and AFAIK hasn't since 2015. Not at home but will check when I get there :)

In the stretch version of Xorg, it is possible to run the Xorg server as a regular user rather than as root. This reduces the risk of privilege escalation via bugs in the X server. However, it has some requirements for working:

It needs logind and libpam-systemd.

The system needs to support Kernel Mode Setting (KMS). Therefore, it may not work in some virtualization environments (e.g. virtualbox) or if the kernel has no driver that supports your graphics card.

It needs to run on the virtual console it was started from.

Only the gdm3 display manager supports running X as a non-privileged user in stretch. Other display managers will always run X as root. Alternatively, you can also start X manually as a non-root user on a virtual terminal via startx.
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