System Update Error "Failed to fetch http://..."

當在做系統update時，出現無法Fetch....的錯誤訊息時，可嘗試下列commands

First confirm that you are able to browse other websites. 

Then, Run this commands:  sudo mv /var/lib/apt/lists{,bakjune4};

sudo mv /var/cache/apt/archives/partial{,bakjune4};

sudo apt-get update;

sudo apt-get upgrade;  

原文出處