Using Alt+F2, I type:
But nothing happens. I am not aware of making any changes and this used to work.
I am using Ubuntu 12.04 LTS 64 bit.
Try pressing Ctrl+Alt+T
This should open a terminal session.
If you want to use Alt+F2, the command to open the terminal is
You can either use the
If you don't know the root password, use
If you press Ctrl + Alt + T to run Terminal
When you are in Terminal, you type sudo before a command if it requires root privileges.