Ubuntu 12.04 LTS download and update are too slow/revision of the software source problem

Problem Description

• In Ubuntu 12.4, no software and updates in other versions were found , and now it can only be done by modifying files; (previously through software and updates , testing the fastest domestic source, automatic selection)
  

problem solved

• Save the original update source configuration:

sudo mv /etc/apt/sources.list /etc/apt/sources.list.backup

• Create a new configuration file:

sudo gedit /etc/apt/sources.list

• Baidu finds the ubuntu mirror station , enters the Tsinghua University open source software mirror station , link https://mirrors.tuna.tsinghua.edu.cn/help/ubuntu/
• Select the system on the left and the version number on the upper side. My one is Ubuntu 12.04 TLS;
  
• Copy and save the content to the file;
  
• Execute the sudo apt-get updatecommand to make the update take effect;
• apt-getThe speed of downloading other software using commands is significantly improved;