August 7th, 2012 
You may have frequently encountered this while trying to install the software from the Ubuntu terminal. It means, that you are already installing the another software through Ubuntu software center or Synaptic Manager. You can install more than one software at a same time.
So, finish for the installation of one software and continue with the other one. But, however if the synaptic manager crashed or you cancel the software installation the process still can be locked. The solution is killing the process and continuing with installing the software. Here’s how you kill the process:
To kill the process, Open terminal and paste following command:
sudo fuser -vki /var/lib/dpkg/lock
Press “Y” to kill the process.
Again, use this command to configure and unpack the packages:
sudo dpkg configure -a
