安装了Ubuntu后，运行sudo apt update时感觉速度一下子就慢下来了，是不是很拉跨？
现在就来将Ubuntu默认的软件源更换为国内的来提升 update与install的速度！
1.先来打开浏览器，进入TUNA的官方软件园界面
单击右部中间的使用帮助进入帮助页面并向下滑动找到ubuntu-ports（使用amd64的请进入ubuntu）
选择Ubuntu版本为18.04 LTS后复制下方链接。
使用ssh登录Ubuntu客户端。
后使用
sudo nano /etc/apt/sources.list
将原本存在的行删除，替换为
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ bionic main restricted universe multiverse
# deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ bionic main restricted universe multiverse
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ bionic-updates main restricted universe multiverse
# deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ bionic-updates main restricted universe multiverse
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ bionic-backports main restricted universe multiverse
# deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ bionic-backports main restricted universe multiverse
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ bionic-security main restricted universe multiverse
# deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ bionic-security main restricted universe multiverse
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ bionic-proposed main restricted universe multiverse
# deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ bionic-proposed main restricted universe multiverse
保存，退出。
在运行sudo apt update试试
是不是就快很多了呢！