ubuntu14.04 Apt-get Install cannot find the software, replace the source solution

After installing 14.04, sometimes using the Apt-get command installation program, will be prompted to find the program, this is because the software source is incorrect, the online said 163, Zhong Ke, Ali and so on, I update the source of the time will be wrong, is generally reported 404 errors, the internet has not found a good way, Suddenly think of my ubun image is from the overseas official http://www.ubuntu.com/download, then the source select the main server can it, try it, yes, Apt-get update will not error, update the source, then use Apt-get install, There will be no software to find the problem, the main server download speed is OK, not very slow, 300kb/s around.

ubuntu14.04 Apt-get Install cannot find the software, replace the source solution