使用Linux的Ubuntu时会很卡，需要更换为阿里源或其他公司的源
步骤：
编辑/etc/apt/sources.list文件
可以使用vi,gedit，小白用gedit会好一点
先备份一个文件
sudo cp /etc/apt/sources.list /etc/apt/sources.list.back
修改内容
sudo gedit /etc/apt/sources.list
替换为
deb http://mirrors.aliyun.com/ubuntu/ focal main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ focal main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ focal-security main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ focal-security main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ focal-updates main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ focal-updates main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ focal-proposed main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ focal-proposed main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ focal-backports main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ focal-backports main restricted universe multiverse
然后更新apt使其生效
apt-get update
附：
阿里镜像站