Ubuntu换国内阿里、清华镜像源

Ubuntu18.04.4系统安装各种依赖的换国内源问题

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

使用指令 lsb_release -a 来查看当前系统的发行版本，
注意到其中的Codename的值

注意到下面的阿里源和清华源中main之前的bionic、bionic-security、bionic-updates这些，Codename的值要和bionic保持一致。

sudo gedit /etc/apt/sources.list
将其清空
确保Codename的值要和bionic保持一致后，将下面的东西添加进/etc/apt/sources.list

#阿里源
deb http://mirrors.aliyun.com/ubuntu/ bionic main restricted universe multiverse
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 multivers