1、ubuntu更新軟件慢，可將軟件源更改爲國內鏡像，以提高下載速度。軟件源配置文件爲/etc/apt/sources.list，首先備份sources.list,切換目錄
cd etc/apt
備份
/etc/apt$ sudo cp sources.list sorces.list.bak
2、打開配置文件
$ sudo gedit sources.list
刪除全部，然後用以下內容（清華鏡像）替換
# 默認註釋了源碼倉庫，如有需要可自行取消註釋
deb https://mirrors.ustc.edu.cn/ubuntu/ xenial main restricted universe multiverse
# deb-src https://mirrors.ustc.edu.cn/ubuntu/ xenial main restricted universe multiverse
deb https://mirrors.ustc.edu.cn/ubuntu/ xenial-updates main restricted universe multiverse
# deb-src https://mirrors.ustc.edu.cn/ubuntu/ xenial-updates main restricted universe multiverse
deb https://mirrors.ustc.edu.cn/ubuntu/ xenial-backports main restricted universe multiverse
# deb-src https://mirrors.ustc.edu.cn/ubuntu/ xenial-backports main restricted universe multiverse
deb https://mirrors.ustc.edu.cn/ubuntu/ xenial-security main restricted universe multiverse
# deb-src https://mirrors.ustc.edu.cn/ubuntu/ xenial-security main restricted universe multiverse
# 預發佈軟件源，不建議啓用
# deb https://mirrors.ustc.edu.cn/ubuntu/ xenial-proposed main restricted universe multiverse
# deb-src https://mirrors.ustc.edu.cn/ubuntu/ xenial-proposed main restricted universe multiverse
更改爲其他鏡像也可以，如阿里雲
#添加阿里源
deb http://mirrors.aliyun.com/ubuntu/ bionic-security main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ bionic-updates main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ bionic-proposed main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ bionic-backports main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ bionic main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ bionic-security main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ bionic-updates main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ bionic-proposed main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ bionic-backports main restricted universe multiverse
3、修改完成後更新源和更新已安裝軟件
$ sudo apt-get update #更新源
$ sudo apt-get upgrade #更新已安裝的包