unity and the tray are not displayed after login

When I'm Log in the Tray bar works. After the correct login it disappear , also the unity bar doesn't appear. so I can not even start a terminal session for making changes, since it does not work the keyboard shortcut to launch it (CTRL + ALT + T). How can I restore the tray and unity bar, provided that this is the problem?

Thanks all.

CTRL + ALT + F1 can be used to bring up a terminal. Once you log in press those keys and type in your username and password (the password will not display, just type it in anyway). Once that is done you will have a functioning terminal. Run the command unity. Then press CTRL + ALT + F7 to return to the desktop.

If Unity is still not running then switch back to the terminal (with CTRL + ALT + F1) and see if there was an error, especially in the "Initializing" section, each of those should lines should end with "...done".

Additional Suggestions:

Try running sudo apt-get install compizconfig-settings-manager followed by export DISPLAY=0:0 followed by ccsm then switch to the desktop, if it comes up make sure that the check box next to unity is checked then go to preferences on the left and click reset to defaults. After that restart the computer and try logging in.

Commands that might work:

xhost +localhost This will add you to the xhosts, I doubt that you aren't in it but probably should try anyway.

/usr/lib/nux/unity_support_test -p Run this command to check if the computer supports unity, if it doesn't you can't run it. In that case I would click the Ubuntu logo on the login screen and select Ubuntu 2D and try that.

unity --reset

sudo rm /etc/X11/xorg.conf This will reset your X11 config file.

If all of those fail you can reinstall unity:

sudo apt-get --purge remove unity
sudo apt-get install unity
sudo services lightdm restart

This will reset all of your graphical settings:

gconftool --shutdown
sudo killall -r -I gconf
sudo killall -r -I dconf
rm -rf .compiz* .gconf* .config/dconf/ .config/compiz*

If that fails this will reinstall the graphical portion of Ubuntu.

sudo apt-get install --reinstall ubuntu-desktop

You can try the same thing with compiz:

sudo apt-get install --reinstall compiz

I've tried john and Erv Gunter answers, however for me what did it was this last line :

sudo apt-get purge nvidia-*
sudo apt-get install ubuntu-desktop
export DISPLAY=:0 
gsettings reset org.compiz.core:/org/compiz/profiles/unity/plugins/core/ active-plugins

source