4.04 源文件地址 已经更换为 /etc/apt/sources.list.d/ubuntu.sources
以更换阿里源为例，受限打开终端，输入以下命令，备份当前的源列表：
cp /etc/apt/sources.list.d/ubuntu.sources /etc/apt/sources.list.d/ubuntu.sources.bak打开文本编辑器，输入以下命令：
nano /etc/apt/sources.list.d/ubuntu.sources在文本编辑器中粘贴以下内容：
阿里云
Types: deb
URIs: http://mirrors.aliyun.com/ubuntu/
Suites: noble noble-updates noble-security
Components: main restricted universe multiverse
Signed-By: /usr/share/keyrings/ubuntu-archive-keyring.gpg保存并关闭文本编辑器。
更新源列表，输入以下命令：
apt update
如果需要，可以更新系统软件包，输入以下命令：
apt upgrade
其他几份国内源如下：
清华源
# 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
Types: deb
URIs: http://mirrors.tuna.tsinghua.edu.cn/ubuntu/
Suites: noble noble-updates noble-security
Components: main restricted universe multiverse
Signed-By: /usr/share/keyrings/ubuntu-archive-keyring.gpg中科大源
Types: deb
URIs: http://mirrors.ustc.edu.cn/ubuntu/
Suites: noble noble-updates noble-security
Components: main restricted universe multiverse
Signed-By: /usr/share/keyrings/ubuntu-archive-keyring.gpg网易163源
Types: deb
URIs: http://mirrors.163.com/ubuntu/
Suites: noble noble-updates noble-security
Components: main restricted universe multiverse
Signed-By: /usr/share/keyrings/ubuntu-archive-keyring.gpg