In Linux, you always wanna to use command: sudo apt-get update to update source list. But if one of terminal doesn't finish updating, and then you execute another same command : sudo apt-get update,it will has the error message like the following :Error output: alicus@ubuntu:~$ sudo apt-get update
E: Could not get lock /var/lib/apt/lists/lock - open (11: Resource temporarily unavailable)
E: Unable to lock the list directory
The solution is :
Open a new terminal console, execute command like this : sudo rm /var/cache/apt/archives/lock ( it is that has been locked ).
After that, you are allowed to execute sudo apt-get update again.
Good luck to you !