[LightDM] can't connect to display before login

[Robert Ancell]

Hi Alfonso,

display-setup-script is run once the X server starts and before anyone
logs in.  session-setup-script is run before a session is started.

Set:
[SeatDefaults]
display-setup-script=/my/script

And set /my/script to :
sudo /usr/bin/x11vnc -noxrecord -noxfixes -noxdamage -rfbauth
/etc/x11vnc.pass -forever -bg -rfbport 5900 -o > /tmp/x11vnc.log

Should do the trick (haven't tested it myself).

On 19 October 2011 14:51, Alfonso Fiore <alfonso.fiore at gmail.com> wrote:
> hi guys,
> it took quite some reading (actually a lot of bad reading and very little
> good reading in the log of x11vnc) but I found a solution.
> Simply I needed to find and use the raw display manager MIT-MAGIC-COOKIE as
> per x11vnc logfile:
> ===============================================
> ** If NO ONE is logged into an X session yet, but there is a greeter login
>    program like "gdm", "kdm", "xdm", or "dtlogin" running, you will need
>    to find and use the raw display manager MIT-MAGIC-COOKIE file.
> Sometimes the command "ps wwwwaux | grep auth" can reveal the file location.
> ===============================================
> which lead me to the right command:
> sudo /usr/bin/x11vnc -auth /var/run/lightdm/root/:0 -noxrecord -noxfixes
> -noxdamage -rfbauth /etc/x11vnc.pass -forever -bg -rfbport 5900 -o
> /tmp/x11vnc.log
> only one question: do you know if lightDM offers a way to run this command
> once lightDM has finished loading?
> Thank you,
> alfonso
> On Wed, Oct 19, 2011 at 1:26 AM, Alfonso Fiore <alfonso.fiore at gmail.com>
> wrote:
>>
>> Hi Robert, Guido,
>> thank you.
>> Indeed the log file was a smart idea ;-)
>> I found quite a telling line there:
>> [+0.01s] WARNING: Can't start VNC server, Xvn is not in the path
>> in fact I used x11vnc and I didn't have any Xvnc installed.
>> So you were all correct, but I still didn't manage :(
>> I tried installing tightvncserver but I got access to a new session, but
>> instead I'm looking to enable desktop sharing. I tried for a good hour to
>> find how to share the main desktop with tightvnc and then I gave up.
>> So I tried also installing vnc4server which has some problem regarding
>> authentication. I get an error in my client: "no password configured for vnc
>> auth" but also I wasn't capable to debug this either. It has probably to do
>> with pam, but I didn't manage to debug the issue:
>> lightdm.log:[+0.90s] DEBUG: pam_start("lightdm-autologin", "lightdm") ->
>> (0x8bef588, 0)
>> lightdm.log:[+0.90s] DEBUG: pam_authenticate(0x8bef588, 0) -> 0 (Success)
>> lightdm.log:[+0.90s] DEBUG: pam_acct_mgmt(0x8bef588, 0) -> 0 (Success)
>> lightdm.log:[+0.91s] DEBUG: pam_set_item(0x8bef588, 3, ":0") -> 0
>> (Success)
>> lightdm.log:[+0.92s] DEBUG: pam_open_session(0x8bef588, 0) -> 0 (Success)
>> lightdm.log:[+0.95s] DEBUG: pam_setcred(0x8bef588, PAM_ESTABLISH_CRED) ->
>> 0 (Success)
>> lightdm.log:[+1.50s] DEBUG: pam_start("lightdm", "alfonso") -> (0x8c06588,
>> 0)
>> I see Xvnc is started as /usr/bin/Xvnc :6 -auth /var/run/lightdm/root/:6
>> -inetd -nolisten tcp but I don't see the -rfbauth to point to the password
>> file. Is there a chance to manually add such option?
>> If I run for example "Xvnc :0 -rfbauth /etc/x11vnc.pass" directly at
>> prompt I can authenticate but still I don't get to share the main desktop.
>> I also tried to create a symbolic link from x11vnc to Xvnc since I know
>> x11vnc works fine, but since x11vnc doesn't have options for running with
>> inetd, it didn't work.
>> Incidentally, at least in Ubuntu 11.10, /var/log/lightdm has
>> permissions drwxr-xr-x but lightdm tries to create log files there with
>> user lightdm and fails. So I had to change permissions to 777.
>> e.g.
>> [+246.83s] WARNING: Failed to open log file
>> /var/log/lightdm/xvnc-6-greeter.log: Permission denied
>> Actually, kind of bad news...
>> From
>> here: http://grumpymole.blogspot.com/2006/12/xubuntu-remote-desktop-with-vnc4server.html?showComment=1167878940000#c1198657880206490449
>> I gather that only x11vnc can share the desktop (is it true?)
>> This is what I'm trying to achieve. Any chance lightdm can support x11vnc
>> as well?
>> Thank you.
>> Good night,
>> alfonso
>> On Wed, Oct 19, 2011 at 12:11 AM, Robert Ancell <robert.ancell at gmail.com>
>> wrote:
>>>
>>> There are multiple Xvnc servers available on Ubuntu, the
>>> tightvncserver package contains one.
>>>
>>> On 19 October 2011 09:08, Guido Berhoerster <gber at opensuse.org> wrote:
>>> > * Alfonso Fiore <alfonso.fiore at gmail.com> [2011-10-18 23:44]:
>>> >> Hello Guido,
>>> >>
>>> >> thank you so much. It sounds great.
>>> >>
>>> >> Now my /etc/lightdm/lightdm.conf looks like:
>>> >>
>>> >> [SeatDefaults]
>>> >> greeter-session=unity-greeter
>>> >> user-session=ubuntu
>>> >>
>>> >> [VNCServer]
>>> >> enabled=true
>>> >> port=5900
>>> >>
>>> >> but after restarting lightdm (sudo restart lightdm) the port is not
>>> >> open:
>>> >>
>>> >> dude at box:~$ netstat -ln | grep 5900
>>> >> dude at box:~$
>>> >>
>>> >> I also tried to reboot, but the result is the same.
>>> >>
>>> >> do you have any suggestion? maybe some missing package?
>>> >
>>> > Do you have Xvnc installed? I don't know what package it's in
>>> > since I don't use Ubuntu.
>>> > --
>>> > Guido Berhoerster
>>> > _______________________________________________
>>> > LightDM mailing list
>>> > LightDM at lists.freedesktop.org
>>> > http://lists.freedesktop.org/mailman/listinfo/lightdm
>>> >
>>
>
>
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