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I upgraded from 13.04 to 13.10 and I can boot to the unity-greeter and login just fine, but after login I just get a black screen with a cursor. I have tried following

Also I have read

All of which were no further help then the two support articles about ATI drivers

So I switched back to the default drivers and went a little further into debugging, when I do ctrl+alt+F1 and login and try unity --debug > unity_start.log then ctrl+alt+F8 the screen stays black with a cursor and when I switch back ctrl+alt+F1 the contents of the log output are

However when I try sudo unity --debug > unity_start_root.log then ctrl+alt+F8, unity starts and the output of the log is

The fact that it starts as root tells be it is either a permissions issue of some required file or there is some setting that is specific to my user that is causing the SIGSEGV.

So to narrow this down I activated the guest account and tried to login and got the same black screens with only a mouse cursor, so this tells me that it is not a configuration issue, but a permissions issue, so how do I narrow down which file has the wrong permissions? Also is there anything further that may help debug this issue?

Ok after a few more hours of googling I found that if I add myself to the video group I can login and see the desktop, but there are lots of other permission related issues, so I am thinking something went wonky with PolicyKit during the upgrade, is there a way to reset PolicyKit settings for a user?

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I had the same problem.

I just fixed it. (kind of) My solution (so you can boot back to GUI) (don't know if it really was this or it was a lot of thing together):

after that I could reboot and login.

OPTIONAL: if you have login loop (type password and is accepted it will re-ask it): (make backup of file)
mv ~/.Xauthority ~/.Xauthority.old and retry to login.

any question, just ask.

cause: I think because old drivers (fglrx) are not supported, so replaced them with supported open-source drivers.

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This did not fix the issue for me. I had to add my user to the video group to get Unity to stop Seg Faulting, and now I see alot of other permission issues – Dj Gilcrease Oct 23 '13 at 18:09
up vote 0 down vote accepted

Ok I was able to fix this I had manually modified several files in /etc/pam.d so I created files in /usr/share/pam-configs that contained the custom modifications and ran sudo dpkg-reconfigure libpam-runtime

Now when I login all permissions work properly and I see no errors on startup

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