ubuntu20.04更换国内源 apt

您好！要在Ubuntu 20.04更换为国内的软件源，可以按照以下步骤操作：

1. 打开终端，可以使用快捷键Ctrl+Alt+T。

2. 备份当前的软件源列表，以防出现问题：

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

3. 编辑软件源列表文件：

   sudo nano /etc/apt/sources.list

4. 在打开的文件中，将原有的内容全部删除，然后将下面的内容粘贴进去：

对于阿里云源：

   # 默认注释了源码镜像以提高 apt update 速度，如有需要可自行取消注释
   # deb-src http://archive.ubuntu.com/ubuntu focal main restricted #Added by software-properties
   
   # 阿里云源
   deb https://mirrors.aliyun.com/ubuntu/ focal main restricted universe multiverse
   deb-src https://mirrors.aliyun.com/ubuntu/ focal main restricted universe multiverse
   
   deb https://mirrors.aliyun.com/ubuntu/ focal-security main restricted universe multiverse
   deb-src https://mirrors.aliyun.com/ubuntu/ focal-security main restricted universe multiverse
   
   deb https://mirrors.aliyun.com/ubuntu/ focal-updates main restricted universe multiverse
   deb-src https://mirrors.aliyun.com/ubuntu/ focal-updates main restricted universe multiverse
   
   deb https://mirrors.aliyun.com/ubuntu/ focal-backports main restricted universe multiverse
   deb-src https://mirrors.aliyun.com/ubuntu/ focal-backports main restricted universe multiverse
   
   ## Not recommended
   # deb https://mirrors.aliyun.com/ubuntu/ focal-proposed main restricted universe multiverse