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I was trying to make the brightness controls work after I had made a clean reinstall of Ubuntu 12.04 on my Gateway computer, based on this thread, and proceeded to restart because I also had a few updates to be done.

Next thing I know, I can't login into the desktop GUI, it flashes a black screen, and gets me back to the login screen.

I then opened up tty6 and logged in with my user and password. I logged in OK, but then immediately this came up:

-bash: groups: commmand not found
Command 'uname' is available in '/bin/uname'

The command could not be located because /bin is not located in the PATH environment variable:

uname: command not found
-bash: [: =: unary operator expected

Several more lines like that and then the command line.

Please help! Maybe I mistyped something when editing the grub file. How would I fix this?

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Log in on a tty1 (Ctrl+Alt+F1) and run these commands:

export PATH="/usr/lib/lightdm/lightdm:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:$PATH"
sudo chown -R $USER:$USER /home/$USER/

You can replace $USER with your actual username.

Now, try logging in again.

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