Ubuntu Apt-get update failed to resolve

When the following error occurs after running Apt-get update:

E:some index files failed to download, they has been ignored ....

Maybe the source of ubuntu16.04 is not good, we just need to change a source.

There are many sources of Ubuntu in China, including: NetEase source (this used before, fast), Ali, there are many sources of education network, such as: Tsinghua source, Zhong Ke source.

Execute command: sudo gedit/etc/apt/sources.list

Here is the source list of Zhong Ke ubuntu16.04, which can be obtained here: https://lug.ustc.edu.cn/repogen/

To edit the/etc/apt/sources.list file, add the following entry at the top of the file (make the appropriate backup before you do the operation):

Deb Http://mirrors.ustc.edu.cn/ubuntu/xenial main restricted universe multiverse
Deb Http://mirrors.ustc.edu.cn/ubuntu/xenial-security main restricted universe multiverse
Deb Http://mirrors.ustc.edu.cn/ubuntu/xenial-updates main restricted universe multiverse
Deb http://mirrors.ustc.edu.cn/ubuntu/xenial-proposed main restricted universe multiverse
Deb Http://mirrors.ustc.edu.cn/ubuntu/xenial-backports main restricted universe multiverse
DEB-SRC http://mirrors.ustc.edu.cn/ubuntu/xenial main restricted universe multiverse
DEB-SRC http://mirrors.ustc.edu.cn/ubuntu/xenial-security main restricted universe multiverse
DEB-SRC http://mirrors.ustc.edu.cn/ubuntu/xenial-updates main restricted universe multiverse
DEB-SRC http://mirrors.ustc.edu.cn/ubuntu/xenial-proposed main restricted universe multiverse
DEB-SRC http://mirrors.ustc.edu.cn/ubuntu/xenial-backports main restricted universe multiverse

Then enter:

sudo apt-get update

Update the source.

Ubuntu Apt-get update failed to resolve