Ubuntu 16.04.3 LTS LightDM Ubuntu Session vanished

Question

I have a pretty weird issue here with the Ubuntu session just vanishing from the LightDM session list. I usually use LXDE/Lubuntu as a session and rarely even log into the Unity/Ubuntu desktop, but it used to work flawless, switching back and forth. Now, all of a sudden, the Ubuntu session isn't listed anymore. I seem to be unable, after some extensive research really, to figure it out by myself. Here is relevant information:

1) The Session is there:

$ ls -al /usr/share/xsessions/
total 36
drwxr-xr-x   2 root root  4096 Jan 24 22:04 .
drwxr-xr-x 313 root root 12288 Feb 15 10:50 ..
-rw-r--r--   1 root root   157 Okt  9 18:02 Lubuntu.desktop
-rw-r--r--   1 root root   165 Okt  9 18:02 Lubuntu-Netbook.desktop
-rw-r--r--   1 root root  1507 Feb 27  2016 LXDE.desktop
-rw-r--r--   1 root root   198 Okt 14  2015 openbox.desktop
-rw-r--r--   1 root root   204 Aug 22  2016 ubuntu.desktop
$ cat /usr/share/xsessions/ubuntu.desktop 
[Desktop Entry]
Name=Ubuntu
Comment=This session logs you into Ubuntu
Exec=gnome-session --session=ubuntu
TryExec=unity
Icon=
Type=Application
DesktopNames=Unity
X-Ubuntu-Gettext-Domain=gnome-session-3.0

2) LightDM lists all sessions, but the Ubuntu session. The log file even explicitly tells that it is ignoring it (see excerpt of the relevant log file):

$ sudo cat /var/log/lightdm/seat0-greeter.log
[...]
[+0,16s] DEBUG: Loaded session /usr/share/xsessions/openbox.desktop (Openbox, Log in using the Openbox window manager (without a session manager))
[+0,16s] DEBUG: Loaded session /usr/share/xsessions/Lubuntu.desktop (Lubuntu, Lubuntu - Lightweight X11 desktop environment based on LXDE)
[+0,16s] DEBUG: Loaded session /usr/share/xsessions/LXDE.desktop (LXDE, LXDE - Lightweight X11 desktop environment)
[+0,16s] DEBUG: Ignoring session /usr/share/xsessions/ubuntu.desktop
[+0,16s] DEBUG: Loaded session /usr/share/xsessions/Lubuntu-Netbook.desktop (Lubuntu Netbook, Lubuntu Netbook - Lubuntu based session for netbook)
[...]
[+3,00s] DEBUG: session-list.vala:49: Adding session LXDE (LXDE)
[+3,00s] DEBUG: session-list.vala:49: Adding session Lubuntu (Lubuntu)
[+3,00s] DEBUG: session-list.vala:49: Adding session Lubuntu-Netbook (Lubuntu Netbook)
[+3,00s] DEBUG: session-list.vala:49: Adding session openbox (Openbox)
[+3,01s] DEBUG: greeter-list.vala:210: Error registering user list dbus object: An object is already exported for the interface com.canonical.UnityGreeter.List at /list

(nm-applet:3866): GLib-GObject-WARNING **: invalid unclassed pointer in cast to 'GtkWidget'

(nm-applet:3866): Gtk-CRITICAL **: gtk_widget_show: assertion 'GTK_IS_WIDGET (widget)' failed
[+8,61s] DEBUG: session-list.vala:49: Adding session LXDE (LXDE)
[+8,61s] DEBUG: session-list.vala:49: Adding session Lubuntu (Lubuntu)
[+8,61s] DEBUG: session-list.vala:49: Adding session Lubuntu-Netbook (Lubuntu Netbook)
[+8,61s] DEBUG: session-list.vala:49: Adding session openbox (Openbox)
[+8,61s] DEBUG: greeter-list.vala:210: Error registering user list dbus object: An object is already exported for the interface com.canonical.UnityGreeter.List at /list
[...]

I did, getting desperate somehow, already try to dpkg-reconfigure both lightdm and ubuntu-session. Didn't do anything.

I did see that "DesktopNames=Unity" is not a FreeDesktop standard definition, but i manually downloaded both "ubuntu-session (3.18.1.2-1ubuntu1)" from xenial and "ubuntu-session (3.18.1.2-1ubuntu1.16.04.2)" from xenial-updates, extracted them, looked at /usr/share/xessions/ubuntu.desktop of each of them and they perfectly match up (i assumed some update to it may have messed it).

My system is up-to-date.

Looks like it is a bug and it has been reported. See linked above. — Terrance, Feb 16 '18 at 04:15
i can confirm what is reported there. ubuntu-desktop isn't installed on my system anymore, unity is marked deinstall (checked that with "dpkg --get-selections"). question now is what to do here: the aptitude fix suggested seems to create more of a mess. are you suggesting to wait for a next update? better yet: is that even automatically repairable still, by the package-manager, with a fix they may just push? i kinda second what other people commented: something like should be tested prior pushing it. also, what am i supposed to do to this thread best (i am new to this site), close it? tyvm — rhorstkoetter, Feb 16 '18 at 04:38
Hmmmm, good question. I actually don't care for Unity or the Ubuntu Desktop. I have become a solid Xfce4 / Xubuntu fan, so none of this affected me at all. So I might not be the right person to give you the advice you need. One would hope though that they will give back the needed dependency that the Ubuntu desktop is calling for so that it can be reinstalled cleanly. Enough votes from users here can close it out in case someone else comes looking and finds the same as you as the close vote will send them to the other question. It's up to you about closing it. — Terrance, Feb 16 '18 at 04:47
i usually install lubuntu-core into an Ubuntu desktop system and use that as my daily driver. Still appreciated being able to use Unity, at times. I decide to wait a while for an eventual update, that (hopefully) gets the systems automatically back in order. Solid advice, ty. The thread i leave as is for now, maybe it is still useful for the community. As i see, a "protected status" was put onto the other thread. That bug introduced there probably makes for some substantial emotions, is my guess. Is there a way for me to "thumbs up" you for the assistance given? appreciate it. — rhorstkoetter, Feb 16 '18 at 05:09
The only thing that you can possibly do here is click the little up flag in front of my comment(s). But it has been a while for me and I can't remember. If you want to earn rep here, start with editing questions and answers. As they get approved you get 2 points per. Answer a question and you get 10 points per upvote, 15 points if your answer is accepted. — Terrance, Feb 16 '18 at 05:36
Sadly, i am not having such flag just yet (probably due to my missing reputation). ty explaining it to me though. i will get back here once i eventually have enough of it and upvote it. — rhorstkoetter, Feb 16 '18 at 05:47
If you look back now on the one that is linked https://askubuntu.com/questions/1006621/2-15-18-compiz-update-broke-unity there is a new answer that actually shows a fix for the dependency issues for the Unity / Ubuntu installation. — Terrance, Feb 16 '18 at 14:53
i saw it, ty, and it helped me. i answered to my own question, hoping that it benefits someone else, providing some information that i couldn't comment on (again due to a missing reputation) within N0bert's answer: For some strange reason i didn't need to explicitly install compiz-core-abiversion-20170630, but i did need to manually reinstall unity and ubuntu-desktop. I accepted N0bert's answer and i have been told that my vote will be counted later, eventually. — rhorstkoetter, Feb 16 '18 at 15:11

score 2 · Answer 1 · answered Feb 16 '18 at 14:55

I am providing an answer to my own question here, as i hope it benefits someone else, stumbling upon that same issue eventually. I have been able to resolve this - thanks to the help of Terrance in this thread and N0rbert in 2/15/18 compiz update broke unity (related issue), all credit goes to them.

Today some update got pushed. All i really did was (again) updating the system, and re-installing both unity and ubuntu-desktop, which was required for me as they apparently got removed earlier.

$ dpkg -l compiz-core
[...]
ii  compiz-core    1:0.9.12.3+1 amd64        OpenGL window and compositing man
$ apt-cache show compiz-core
Package: compiz-core
Architecture: amd64
Version: 1:0.9.12.3+16.04.20171116-0ubuntu1
[...]
Provides: compiz-core-abiversion-20170630
[...]
$ sudo apt-get install unity ubuntu-desktop
[...]

Explicitly installing compiz-core-abiversion-20170630 was not even required for me. Manually reinstalling unity and ubuntu-desktop was necessary though.

Doing this, my LightDM session list is back to normal and i can start a Unity/Ubuntu Desktop session (again), that seems to be working OK thus far.

Thanks again for pointing me into the very right direction, Terrance. A missing reputation is a bit restrictive, starting out (but understandable); otherwise i could have just added my feedback, i.e. my very slightly different experience, directly to N0bert's answer. — rhorstkoetter, Feb 16 '18 at 15:28

Ubuntu 16.04.3 LTS LightDM Ubuntu Session vanished

1 Answers1