Change Armbian Source
N1安装Armbian系统后，使用的是国外官方源，速度不友好，于是替换为国内镜像源，来提高下载更新速度显得尤为重要。
使用 lsb_release -a命令可以查看系统版本情况，比如我的N1系统如下所示：
root@aml:~# lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 18.04.5 LTS
Release: 18.04
Codename: bionic
然后，备份系统自带源文件，命令 sudo cp /etc/apt/sources.list /etc/apt/sources.list.bak;
接着将如下中科大的源，替换/etc/apt/sources.list内的内容，
deb http://mirrors.ustc.edu.cn/ubuntu-ports/ bionic main multiverse restricted universe
deb http://mirrors.ustc.edu.cn/ubuntu-ports/ bionic-backports main multiverse restricted universe
deb http://mirrors.ustc.edu.cn/ubuntu-ports/ bionic-proposed main multiverse restricted universe
deb http://mirrors.ustc.edu.cn/ubuntu-ports/ bionic-security main multiverse restricted universe
deb http://mirrors.ustc.edu.cn/ubuntu-ports/ bionic-updates main multiverse restricted universe
deb-src http://mirrors.ustc.edu.cn/ubuntu-ports/ bionic main multiverse restricted universe
deb-src http://mirrors.ustc.edu.cn/ubuntu-ports/ bionic-backports main multiverse restricted universe
deb-src http://mirrors.ustc.edu.cn/ubuntu-ports/ bionic-proposed main multiverse restricted universe
deb-src http://mirrors.ustc.edu.cn/ubuntu-ports/ bionic-security main multiverse restricted universe
deb-src http://mirrors.ustc.edu.cn/ubuntu-ports/ bionic-updates main multiverse
替换完成后，使用命令 sudo apt update && sudo apt upgrade命令更新系统文件即可。