备份原来的源：
sudo cp /etc/apt/sources.list /etc/apt/sources.list.bak
更换源:
sudo vim /etc/apt/sources.list
将里面文件内容全部替换成下面：
#deb包
deb http://mirrors.aliyun.com/ubuntu/ xenial main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ xenial-security main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ xenial-updates main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ xenial-backports main restricted universe multiverse
##测试版源
deb http://mirrors.aliyun.com/ubuntu/ xenial-proposed main restricted universe multiverse
# 源码
deb-src http://mirrors.aliyun.com/ubuntu/ xenial main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ xenial-security main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ xenial-updates main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ xenial-backports main restricted universe multiverse
##测试版源
deb-src http://mirrors.aliyun.com/ubuntu/ xenial-proposed main restricted universe multiverse
# Canonical 合作伙伴和附加
deb http://archive.canonical.com/ubuntu/ xenial partner
deb http://extras.ubuntu.com/ubuntu/ xenial main
执行更新：
sudo apt-get update
复损坏的软件包，尝试卸载出错的包，重新安装正确版本的:
sudo apt-get -f install
更新软件:
sudo apt-get upgrade
更新源位置：/etc/apt/sources.list
源的内容：
deb cn.archive.ubuntu.com/ubuntu/ bionic main restricted universe multiverse
cdrom:安装的时候用的老旧的源
第一列：deb表示安装包，deb-src表示源码包
第二列：软件仓库的url地址
第三列：系统的codename
sudo lsb_release -a查看系统信息
第四列：库的内容构成
main：官方支持，提供源码，官方维护bug
restricted：官方支持，不提供源码
universe：社区支持
multiverse：不开源，没有支持，可能存在危险
