修改源列表，按着键盘DD删除原来的源，并按键盘的i键进入插入下面的源
vi /etc/apt/sources.list阿里云源
deb http://mirrors.aliyun.com/debian stretch main contrib non-free
deb-src http://mirrors.aliyun.com/debian stretch main contrib non-free
deb http://mirrors.aliyun.com/debian stretch-updates main contrib non-free
deb-src http://mirrors.aliyun.com/debian stretch-updates main contrib non-free
deb http://mirrors.aliyun.com/debian-security stretch/updates main contrib non-free
deb-src http://mirrors.aliyun.com/debian-security stretch/updates main contrib non-free其他源
# deb cdrom:[Debian GNU/Linux 10.0.0 _Buster_ - Official amd64 NETINST 20190706-10:23]/ buster main
#deb cdrom:[Debian GNU/Linux 10.0.0 _Buster_ - Official amd64 NETINST 20190706-10:23]/ buster main
deb http://mirror.clayer.net/debian/ buster main
deb-src http://mirror.clayer.net/debian/ buster main
deb http://security.debian.org/debian-security buster/updates main
deb-src http://security.debian.org/debian-security buster/updates main
# buster-updates, previously known as 'volatile'
deb http://mirror.clayer.net/debian/ buster-updates main
deb-src http://mirror.clayer.net/debian/ buster-updates main完成后，两条命令敲下更新即可
apt-get update
apt-get upgrade
