PAS 配置sources.list软件源
参考例子（Debian 9，文件/etc/apt/sources.list）:
deb https://mirrors.ustc.edu.cn/debian/ stretch main contrib non-free
deb-src https://mirrors.ustc.edu.cn/debian/ stretch main contrib non-free
deb https://mirrors.ustc.edu.cn/debian/ stretch-updates main contrib non-free
deb-src https://mirrors.ustc.edu.cn/debian/ stretch-updates main contrib non-free
deb https://mirrors.ustc.edu.cn/debian/ stretch-backports main contrib non-free
deb-src https://mirrors.ustc.edu.cn/debian/ stretch-backports main contrib non-free
deb https://mirrors.ustc.edu.cn/debian-security/ stretch/updates main contrib non-free
deb-src https://mirrors.ustc.edu.cn/debian-security/ stretch/updates main contrib non-free国内的软件源镜像（Arch Linux, Centos, Debian, Fedora, OpenSUSE, Ubuntu等）：
Debian/Ubuntu的软件源配置文件在/etc/apt/sources.list，具体可以参见相关镜像网站的配置帮助。
在线配置网站：USTC repository file generator
- Debain 参考手册（中文版）
sources.list中使用https，需要安装apt-transport-https
PAS apt search精确匹配包名
- 方式一：使用正则表达式
apt search ^packagename$- 方式二：使用命令参数
apt search --names-only packagename
- apt search: limit to exact match, askubuntu.com
PAS 关于Ubuntu PPA
- update-alternatives: display, install, remove, config
- PPA，或是Personal Package Archive（个人软件包存档）：不一定是官方
sudo add-apt-repository ppa_name
sudo apt-get update
sudo apt-get install 软件名称
PAS Linux更新出现error The following signatures couldn't be verified because the public key is not available错误
apt-key adv --recv-keys --keyserver keyserver.ubuntu.com 3B4FE6ACC0B21F32
apt-key adv --recv-keys --keyserver keyserver.ubuntu.com 40976EAF437D05B5
gpg --keyserver wwwkeys.pgp.net --recv-keys AED4B06F473041FA
gpg -a --export AED4B06F473041FA |apt-key add -