Ubuntu更換清華鏡像源——更快的下載速度

由於ubuntu自帶的軟件源下載速度很慢，尤其對於國外的網站進行訪問時，所以可以修改軟件源，更快更穩定的下載安裝各種包。

步驟如下：

1、先備份源文件：

cd /etc/apt/
sudo cp sources.list sources.list.bak 

2、替換源文件：

sudo gedit sources.list

修改爲：

# 默認註釋了源碼鏡像以提高 apt update 速度，如有需要可自行取消註釋
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial main restricted universe multiverse
# deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial main restricted universe multiverse
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-updates main restricted universe multiverse
# deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-updates main restricted universe multiverse
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-backports main restricted universe multiverse
# deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-backports main restricted universe multiverse
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-security main restricted universe multiverse
# deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-security main restricted universe multiverse
 
# 預發佈軟件源，不建議啓用
# deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-proposed main restricted universe multiverse
# deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-proposed main restricted universe multiverse

3、更新源文件：

sudo apt-get update 更新源  
sudo apt-get upgrade 更新軟件