ubuntu系统，源需要更换成下面的：
vim /etc/apt/sources.list
deb http://mirrors.ustc.edu.cn/ubuntu-ports/ bionic main restricted universe multiverse
#deb-src http://mirrors.ustc.edu.cn/ubuntu-ports/ bionic main restricted universe multiverse
deb http://mirrors.ustc.edu.cn/ubuntu-ports/ bionic-security main restricted universe multiverse
#deb-src http://mirrors.ustc.edu.cn/ubuntu-ports/ bionic-security main restricted universe multiverse
deb http://mirrors.ustc.edu.cn/ubuntu-ports/ bionic-updates main restricted universe multiverse
#deb-src http://mirrors.ustc.edu.cn/ubuntu-ports/ bionic-updates main restricted universe multiverse
deb http://mirrors.ustc.edu.cn/ubuntu-ports/ bionic-backports main restricted universe multiverse
#deb-src http://mirrors.ustc.edu.cn/ubuntu-ports/ bionic-backports main restricted universe multiverse
顺便还可以替换一下armbian的源
/etc/apt/sources.list.d/armbian.list替换成下面的内容
deb https://mirrors.tuna.tsinghua.edu.cn/armbian stretch main stretch-utils stretch-desktop
