I got problem with changing users. I got two user accounts, one root and one normal user. When normal user login and after a while lock screen appears or you try to change user and you press change user, you got a black screen, no back-light or nothing but i can hear Ubuntu tune playing.

After using terminal command startx i end up looking root user background or got an error message that tells unable to connect to x server: Connection refused. Only reboot helps or it's only thing i know how to do it. :)

So is this something i can fix by reinstalling something or is this something i should report as a bug?

Ubuntu 13.10, Gallium 0.4 on AMD ARUBA(using one graphic card..), Dual graphics AMD Radeon hd7640g + 7600m.

Computer Samsung Series3 np355v5c-s08se


I had a similar problem, but with proprietary drivers for an NVIDIA graphics card. I had used the nvidia-319-updates package which seems to automatically update the proprietary driver to latest versions. Switching to the tested nvidia-319 made the problem disappear.

As you seem to have AMD, try a different or free driver to see if that's the cause. You can use the "Software & Updates" program on tab "Additional Drivers" to select the driver.

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  • I think problem might be something to do about graphic drivers. I've learn new things about my computer and i notice that i have dual graphics(updated details to original message). But my Ubuntu know only one. I know that Ubuntu supports dual graphics but i haven been able to find good proprietary driver installation guide for dual graphics. Somehow i always end up watching black screen and doing Ubuntu re-installation.. – Lauri Nov 29 '13 at 14:19

Start your solution by opening the terminal (Alt+Ctrl+T) and enter:

sudo /usr/lib/lightdm/lightdm-set-defaults --show-manual-login true

Restart the computer, hope it will work, if it doesn't remove ~/.Xauthority in home by

sudo rm ~/.Xauthority

then you can easily login.

If you have installed cinammon then, try the following:

sudo apt-get remove --purge cinnamon*`
sudo apt-get autoremove

If you don't have cinnamon installed but any other desktop environment alongside Unity, try to uninstall those. (Gnome fallback should be fine though). hope it will work.

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  • Hi, I try what you suggest but it didn’t help. I even notify typo, but didn't help. – Lauri Nov 29 '13 at 13:49

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