Desktop login fails, terminal works

Question

I have a freshly setup 12.04 LTS pc system (120 GB SSD, 1 TB HDD, 16 GiB RAM); since a few days, I can't login to the graphical desktop anymore: there is very short flashing shell window which disappears very quickly (edit: see below), and I'm confronted with the login screen again. I believe there is something about modprobe and vbox, but I can't read it fast enough ...

I can login to a terminal (Ctrl+Alt+F1). It did not help to chown all contents of my home directory to me:my-group, like suggested here.

This is what I could find in /var/log, grepping for the date and time (I inserted linebreaks after <my-hostname>; real time values preserved):

auth.log:

<date> 22:43:01 <my-hostname>
    lightdm: pam_succeed_if(lightdm:auth): requirement "user ingroup nopasswdlogin" not met by user "tobias"
<date> 22:43:08 <my-hostname>
    lightdm: pam_unix(lightdm:session): session closed for user lightdm
<date> 22:43:08 <my-hostname>
    lightdm: pam_unix(lightdm:session): session opened for user tobias by (uid=0)
<date> 22:43:08 <my-hostname>
    lightdm: pam_ck_connector(lightdm:session): nox11 mode, ignoring PAM_TTY :0
<date> 22:43:08 <my-hostname>
    lightdm: pam_unix(lightdm:session): session closed for user tobias
<date> 22:43:09 <my-hostname>
    lightdm: pam_unix(lightdm:session): session opened for user lightdm by (uid=0)
<date> 22:43:09 <my-hostname>
    lightdm: pam_ck_connector(lightdm:session): nox11 mode, ignoring PAM_TTY :0
<date> 22:43:10 <my-hostname>
    lightdm: pam_succeed_if(lightdm:auth): requirement "user ingroup nopasswdlogin" not met by user "tobias"
<date> 22:43:10 <my-hostname>
    dbus[756]: [system] Rejected send message, 2 matched rules; type="method_call", sender="1:43" (uid=104 pid=1639 comm="/usr/lib/indicator-datetime/indicator-datetime-ser") interface="org.freedesktop.DBus.Properties" member="GetAll" error name="(unset)" requested_reply="0" destination=":1.15" (uid=0 pid=1005 comm="/usr/sbin/console-kit-daemon --no-daemon ")

kern.log:

<date> 22:43:00 <my-hostname>
    kernel: [   16.084525] eth0: no IPv6 routers present

syslog:

<date> 22:43:00 <my-hostname>
    kernel: [   16.084525] eth0: no IPv6 routers present
<date> 22:43:01 <my-hostname>
    ntpdate[1492]: adjust time server 91.189.94.4 offset -0.162831 sec
<date> 22:43:08 <my-hostname>
    acpid: client 969[0:0] has disconnected
<date> 22:43:08 <my-hostname>
    acpid: client connected from 1553[0:0]
<date> 22:43:08 <my-hostname>
    acpid: 1 client rule loaded

I have Virtualbox and Truecrypt installed, but I can't think of a reason why they might prevent a graphical login.

I'm confused:

• What is this about requirement "user ingroup nopasswdlogin" not met? I do login using a password, and the password works ok when logging in to a terminal!
• Can I somehow read the error output, e.g. by delaying it, redirecting it to a file, or having the system prompt me for pressing a key?
• Has possibly any recent update caused my problem? Should I install the pending updates? How, btw, without access to the graphical UI?

I have some working knowledge about the Linux shell, but I'm new to Ubuntu. Any help would be appreciated.

Edit: After shutting down the machine yesterday (sudo shutdown now), I found the following text on the screen, which appears to be the "flashing" text mentioned before (formatted; there was some silly leading whitespace):

Could not write bytes: broken pipe
speech-dispatcher disabled; edit /etc/default/speed-dispatcher
* Starting VirtualBox kernel modules
* modprobe vboxdrv failed. Please use 'dmesg' to find out why
saned disabled; edit /etc/default/saned
* Checking battery state... [ OK ]

After manually copying it, I switched the machine off by pressing the button several seconds.

Might be that virtualbox (4.2 installed) causes the problem. I'll add some more log file extractions later today (MET).

Edit, for the records: I tried the following, from /a/133754/103086:

• sudo apg-get install gdm (when prompted, chose GDM)
• rebooted; login failed with GDM, too
• sudo dpkg-reconfigure lightdm, rebooted; login won't work
• my ~/.Xauthority file is empty; deleting it and rebooting didn't change anything

Furthermore:

• deinstalled virtualbox (sudo apt-get remove virtualbox-4.2), rebooting

Edit: I uploaded a zip archive of selected/filtered log files to http://www.tobias-herp.de/en/errors/ubuntu-gui-lockout. Kept apt-get upgradeing recently, but unfortunately the problem persists.

Answer 1

I finally gave up and reinstalled the system. This was not a problem, since the system was quite fresh, and most personal data was not yet migrated to it. I can't tell for sure the problem was not caused by a non-standard package, so ...

So I started anew, and I took precautions to be better off next time. After installation, I updated the system, installed some crucial packages and pinned an eye to the configuration:

sudo bash
apt-get upgrade
apt-get install ssh mercurial vim
cd /etc/
vim mercurial/hgrc
hg init .
hg add *
hg commit

Thus, whenever a new problem occurs, I should stand a better chance to know what might have gone wrong.

Answer 2

Running into this now using lightdm + any non unity greeter. If I set the greeter to unity-greeter in /etc/lightdm/lightdm.conf, it seems to work. No idea why.

Edit: redacted. Something I just pulled in with an update must have caused this and now even the unity greeter doesn't work.

Answer 3

In my case I added some commands into .xprofile which caused the return back to login-screen right after login. The errors I found were the same. Remove everything non-essential from your ~/.profile and ~/.xprofile should bring the situation back to normal.

Answer 4

I had this same issue. It turned out that my problem was that ~/.Xauthority was updated as root, and from then on only root could read it. It stopped me from starting any X session from my username. I had to sudo rm ./.Xauthority and it worked fine after that.