Bug#818152: lightdm: can no longer manage multiple X servers

[Christian Pernegger]

Package: lightdm
Version: 1.16.7-1
Severity: important
Tags: upstream

Hello,

I've just spent the better part of a day trying to get lightdm to
spawn multiple instances as suggested in the config file and various
older forum posts and howtos -- just to finally find out that it
doesn't do that anymore and silently ignores any manually configured
additional "seats":
https://lists.freedesktop.org/archives/lightdm/2014-August/000661.html.

This should at the very least be documented in the default config file
and NEWS (not buried in the changelog for 1.11.7), better yet ignored
configuration should throw a warning.

The behaviour itself breaks a use case of mine, namely launching
multiple persistent VNC servers as shared "graphical consoles". That
wouldn't be that much of a problem if I could just switch dms, but
gdm3, whatever-KDE's-dm-is-called-now and lxdm don't support launching
multiple servers anymore either. It's all systemd/logind now ... ...

Any chance to add manual configuration back?

Regards,
Christian



-- System Information:
Debian Release: stretch/sid
APT prefers testing-updates
APT policy: (500, 'testing-updates'), (500, 'testing')
Architecture: amd64 (x86_64)

Kernel: Linux 4.3.0-1-amd64 (SMP w/2 CPU cores)
Locale: LANG=de_AT.UTF-8, LC_CTYPE=de_AT.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages lightdm depends on:
ii adduser 3.113+nmu3
ii dbus 1.10.6-1
ii debconf [debconf-2.0] 1.5.58
ii libaudit1 1:2.4.5-1+b1
ii libc6 2.21-9
ii libgcrypt20 1.6.5-2
ii libglib2.0-0 2.46.2-3
ii libpam-systemd 229-2
ii libpam0g 1.1.8-3.2
ii libxcb1 1.11.1-1
ii libxdmcp6 1:1.1.2-1.1
ii lightdm-gtk-greeter [lightdm-greeter] 2.0.1-2

Versions of packages lightdm recommends:
ii xserver-xorg 1:7.7+13

Versions of packages lightdm suggests:
ii accountsservice 0.6.40-3
ii upower 0.99.4-2

-- Configuration Files:
/etc/lightdm/lightdm.conf changed [not included]

-- debconf information excluded

[Yves-Alexis Perez]

On lun., 2016-03-14 at 11:00 +0100, Christian Pernegger wrote:

Hi,

> […]

First you should try to investigate whether it's possible to port your setup
to logind.

> This should at the very least be documented in the default config file
> and NEWS (not buried in the changelog for 1.11.7), better yet ignored
> configuration should throw a warning.

We might add a NEWS entry, but honestly I have the feeling you might be the
only user of that feature (nobody complained so far; I know it didn't reach a
Debian stable release yet, but it did in Ubuntu).

> Any chance to add manual configuration back?

You need to port your case directly upstream (see the last paragraph of the
mail)

Regards,
--
Yves-Alexis

[Christian Pernegger]

2016-03-14 17:20 GMT+01:00 Yves-Alexis Perez <cor...@debian.org>:
> First you should try to investigate whether it's possible to port your setup
> to logind.

I've found an ugly workaround:

1) Start the Xvnc instances standalone (e.g.via systemd).

2) Add lightdm to them using "dm-tool add-local-x-seat".
This way lightdm doesn't manage the display but at least provides a
greeter and working login. The only problem is that lightdm won't
restart by itself once the session exits and there's no way to tell
systemd to restart it because it can't track the added seat.

3) Enable the session-cleanup-script and add another "local-x-seat" on
the same display there.
The result works more or less, but there's no session tracking in
logind and I'm not sure if some session processes don't stick around.

> honestly I have the feeling you might be the only user of that feature

Google searches show that this kind of setup was quite popular until
2012 or so when some widespread distro changes invalidated the usual
recipies. I have no idea how people realise that use-case now. Until
recently I was happily using gdm2 on whatever stable was called ca.
2009 ^^.

Note that this isn't a lightdm problem, it affects all current dms as
far as I could find. My issue with lightdm is the documentation more
than the loss of functionality:
* It suggests that it can start multiple servers configured in
/etc/lightdm.conf (it can't, anymore).
* It documents dm-tool add-seat (which doesn't work anymore).
* The session cleanup script should run "when quitting a user
session", but it's also called when you change from the user to the
password field on the login screen (?!?).
(I should probably file these as separate bugs, but I don't have
enough time right now, sorry.)

Regards,
Christian

[Oleg Kostyuk]

Hi Yves-Alexis Perez,

Very sorry but you are wrong, there are more users that need that.

Not much but still.

Personally I wanted to configure multi-session support in Xorg (not multi-seat).

As I see, there is no way to do that on Debian 9.

What about to "nobody complained" - well, I'm complaining now, and just because I've got new hardware and tried to setup fresh system. I had no need to complain earlier because my old system (Debian 7) still works fine and does what I needed. Now I see no other option to get what I want on new hardware except to setup Debian 7.

I will be glad if I understood something wrong, and Xorg multi-session is possible on current Debian 9 (any DM will be fine for me).

If so, please reply here or into my message in users mailing list: https://lists.debian.org/debian-user/2017/10/msg00335.html

Hope this will be solved.

Thank you!

On Mon, 14 Mar 2016 17:20:45 +0100 Yves-Alexis Perez <cor...@debian.org> wrote:

> On lun., 2016-03-14 at 11:00 +0100, Christian Pernegger wrote:

> 

> Hi,

> 

> > […]

> 

> First you should try to investigate whether it's possible to port your setup

> to logind.

> 

> > This should at the very least be documented in the default config file

> > and NEWS (not buried in the changelog for 1.11.7), better yet ignored

> > configuration should throw a warning.

> 

> We might add a NEWS entry, but honestly I have the feeling you might be the

> only user of that feature (nobody complained so far; I know it didn't reach a

> Debian stable release yet, but it did in Ubuntu).

> > Any chance to add manual configuration back?

> 

> You need to port your case directly upstream (see the last paragraph of the

> mail)

> 

> Regards,

> -- 

> Yves-Alexis

> 

--

Sincerely yours,
Oleg Kostyuk (CUB-UANIC)