安装好ubuntu系统后，默认的软件更新源是国外的，在国内使用速度很慢，用"apt install xxx"安装软件时可能出现"网络不可达"、"你的网络需要认证吗"、"无法定位软件包"等错误，所以我们需要更换成国内的源，这样才能正常安装和更新软件。

1.备份原始源文件source.list

打开终端，执行命令：

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

或启动超级用户的文件管理器

sudo nautilus

2.修改源文件sources.list

执行命令：

sudo gedit /etc/apt/sources.list

打开文件进行编辑,删除原来的文件内容，复制下面的任意一个到其中并保存（常用的是阿里源和清华源，推荐阿里源）；

阿里源

 deb http://mirrors.aliyun.com/ubuntu/ jammy main restricted universe multiverse
 deb-src http://mirrors.aliyun.com/ubuntu/ jammy main restricted universe multiverse

 deb http://mirrors.aliyun.com/ubuntu/ jammy-security main restricted universe multiverse
 deb-src http://mirrors.aliyun.com/ubuntu/ jammy-security main restricted universe multiverse

 deb http://mirrors.aliyun.com/ubuntu/ jammy-updates main restricted universe multiverse
 deb-src http://mirrors.aliyun.com/ubuntu/ jammy-updates main restricted universe multiverse

 deb http://mirrors.aliyun.com/ubuntu/ jammy-proposed main restricted universe multiverse
 deb-src http://mirrors.aliyun.com/ubuntu/ jammy-proposed main restricted universe multiverse

 deb http://mirrors.aliyun.com/ubuntu/ jammy-backports main restricted universe multiverse
 deb-src http://mirrors.aliyun.com/ubuntu/ jammy-backports main restricted universe multiverse

清华源

 deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ jammy main restricted universe multiverse
 deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ jammy main restricted universe multiverse

 deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ jammy-security main restricted universe multiverse
 deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ jammy-security main restricted universe multiverse

 deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ jammy-updates main restricted universe multiverse
 deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ jammy-updates main restricted universe multiverse

 deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ jammy-proposed main restricted universe multiverse
 deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ jammy-proposed main restricted universe multiverse

 deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ jammy-backports main restricted universe multiverse
 deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ jammy-backports main restricted universe multiverse

3.更新源

更改完成之后执行以下命令

 sudo apt update
 sudo apt upgrade