Ubuntu18.04修改apt-get源

1）备份源文件：

sudo cp /etc/apt/sources.list /etc/apt/sources.list.bak

2）查看版本信息

如是Linux Mint等Ubuntu衍生版，执行：

cat /etc/upstream-release/lsb-release

如是Ubuntu直接执行：

lsb_release -c

确认当前系统代号（Codename）为：bionic。如是其他版本，请使用其他版本的软件源，其中：

Ubuntu 12.04 (LTS)代号为precise。
Ubuntu 14.04 (LTS)代号为trusty。
Ubuntu 15.04 代号为vivid。
Ubuntu 15.10 代号为wily。
Ubuntu 16.04 (LTS)代号为xenial。
Ubuntu 18.04 (LTS)代号为bionic

3）修改sources.list：

修改/etc/apt/sources.list为以下内容：

deb http://mirrors.aliyun.com/ubuntu/ bionic main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ bionic main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ bionic-security main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ bionic-security main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ bionic-updates main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ bionic-updates main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ bionic-backports main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ bionic-backports main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ bionic-proposed main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ bionic-proposed main restricted universe multiverse

3.1) for Ubunto 20

sudo sed "s/bionic/$(lsb_release -c | awk '{print $2}')/g" /etc/apt/sources.list

4）检查更新

sudo apt-get update

5）可选操作：移除原有源

cd /etc/apt/sources.list.d
sudo mv official-package-repositories.list official-package-repositories.list.bak