vim /etc/apt/sources.list

deb http://mirrors.ustc.edu.cn/ubuntu-ports/ focal main multiverse restricted universe
deb http://mirrors.ustc.edu.cn/ubuntu-ports/ focal-backports main multiverse restricted universe
deb http://mirrors.ustc.edu.cn/ubuntu-ports/ focal-proposed main multiverse restricted universe
deb http://mirrors.ustc.edu.cn/ubuntu-ports/ focal-security main multiverse restricted universe
deb http://mirrors.ustc.edu.cn/ubuntu-ports/ focal-updates main multiverse restricted universe
deb-src http://mirrors.ustc.edu.cn/ubuntu-ports/ focal main multiverse restricted universe
deb-src http://mirrors.ustc.edu.cn/ubuntu-ports/ focal-backports main multiverse restricted universe
deb-src http://mirrors.ustc.edu.cn/ubuntu-ports/ focal-proposed main multiverse restricted universe
deb-src http://mirrors.ustc.edu.cn/ubuntu-ports/ focal-security main multiverse restricted universe
deb-src http://mirrors.ustc.edu.cn/ubuntu-ports/ focal-updates main multiverse restricted universe

# 根据设备具体情况删除/增加默认路由
route del default
route del default
route add default gw 192.168.1.200 eth1

vim /etc/resolv.conf

nameserver 192.168.1.200