Ubuntu18.04 source.list怎么更新国内源

要更新Ubuntu 18.04的软件源为国内源，可以按照以下步骤进行操作：

1. 打开终端，通过以下命令备份当前的软件源列表文件：

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

2. 编辑软件源列表文件，使用以下命令打开编辑器：

sudo nano /etc/apt/sources.list

3. 在打开的文件中，删除所有内容，然后粘贴以下内容，这是一个推荐的国内源列表：

# 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/ bionic main restricted

# 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 http://mirrors.aliyun.com/ubuntu/ bionic main restricted
# deb-src http://mirrors.aliyun.com/ubuntu/ bionic main restricted

deb http://mirrors.aliyun.com/ubuntu/ bionic-updates main restricted
# deb-src http://mirrors.aliyun.com/ubuntu/ bionic-updates main restricted

deb http://mirrors.aliyun.com/ubuntu/ bionic universe
# deb-src http://mirrors.aliyun.com/ubuntu/ bionic universe
deb http://mirrors.aliyun.com/ubuntu/ bionic-updates universe
# deb-src http://mirrors.aliyun.com/ubuntu/ bionic-updates universe

deb http://mirrors.aliyun.com/ubuntu/ bionic multiverse
# deb-src http://mirrors.aliyun.com/ubuntu/ bionic multiverse
deb http://mirrors.aliyun.com/ubuntu/ bionic-updates multiverse
# deb-src http://mirrors.aliyun.com/ubuntu/ bionic-updates 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

# 预发布软件源，不建议启用
# 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

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

4. 保存更改并关闭编辑器。对于Nano编辑器，请按Ctrl + X，然后按Y，最后按Enter保存文件。

5. 运行以下命令更新软件源：

sudo apt update

现在，您的Ubuntu 18.04系统的软件源已更新为国内源。您可以使用apt命令安装和更新软件包，速度应该会更快。