Ubuntu 18.04清华镜像源

Ubuntu 18.04的清华镜像源可以使用以下命令进行设置：

1.备份原有的源列表文件：

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

2.编辑源列表文件：

sudo nano /etc/apt/sources.list

3.在文件中添加以下内容（请根据自己的位置选择镜像源）：

#清华大学镜像源
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic main restricted universe multiverse
deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic main restricted universe multiverse
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic-updates main restricted universe multiverse
deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic-updates main restricted universe multiverse
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic-backports main restricted universe multiverse
deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic-backports main restricted universe multiverse
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic-security main restricted universe multiverse
deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic-security main restricted universe multiverse

4.保存并退出文件，然后运行以下命令更新源：

sudo apt update

5.更新软件包：

sudo apt upgrade