1.备份原始源文件sources.list
①打开终端，执行命令
sudo cp /etc/apt/sources.list /etc/apt/sources.list.bak2.修改源文件 sources.list
①打开终端，执行命令
# 更改文件权限使其可编辑sudo chmod 777 /etc/apt/sources.list②执行命令
# 打开文件进行编辑sudo gedit /etc/apt/sources.list
③删除原来的文件内容，复制下面的任意一个到其中保存（常用的是qsddt和清华源，推荐qsddt，不同Ubuntu版本的镜像源有不同，内容可以去博客复制）
qsddt：deb http://mirrors.aliyun.com/ubuntu/ bionic main restricted universe multiversedeb http://mirrors.aliyun.com/ubuntu/ bionic-security main restricted universe multiversedeb http://mirrors.aliyun.com/ubuntu/ bionic-updates main restricted universe multiversedeb http://mirrors.aliyun.com/ubuntu/ bionic-proposed main restricted universe multiversedeb http://mirrors.aliyun.com/ubuntu/ bionic-backports main restricted universe multiversedeb-src http://mirrors.aliyun.com/ubuntu/ bionic main restricted universe multiversedeb-src http://mirrors.aliyun.com/ubuntu/ bionic-security main restricted universe multiversedeb-src http://mirrors.aliyun.com/ubuntu/ bionic-updates main restricted universe multiversedeb-src http://mirrors.aliyun.com/ubuntu/ bionic-proposed main restricted universe multiversedeb-src http://mirrors.aliyun.com/ubuntu/ bionic-backports main restricted universe multiverse中科大源：deb https://mirrors.ustc.edu.cn/ubuntu/ bionic main restricted universe multiversedeb-src https://mirrors.ustc.edu.cn/ubuntu/ bionic main restricted universe multiversedeb https://mirrors.ustc.edu.cn/ubuntu/ bionic-updates main restricted universe multiversedeb-src https://mirrors.ustc.edu.cn/ubuntu/ bionic-updates main restricted universe multiversedeb https://mirrors.ustc.edu.cn/ubuntu/ bionic-backports main restricted universe multiversedeb-src https://mirrors.ustc.edu.cn/ubuntu/ bionic-backports main restricted universe multiversedeb https://mirrors.ustc.edu.cn/ubuntu/ bionic-security main restricted universe multiversedeb-src https://mirrors.ustc.edu.cn/ubuntu/ bionic-security main restricted universe multiversedeb https://mirrors.ustc.edu.cn/ubuntu/ bionic-proposed main restricted universe multiversedeb-src https://mirrors.ustc.edu.cn/ubuntu/ bionic-proposed main restricted universe multiverse清华源：deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic main restricted universe multiversedeb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic main restricted universe multiversedeb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic-updates main restricted universe multiversedeb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic-updates main restricted universe multiversedeb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic-backports main restricted universe multiversedeb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic-backports main restricted universe multiversedeb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic-security main restricted universe multiversedeb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic-security main restricted universe multiversedeb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic-proposed main restricted universe multiversedeb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic-proposed main restricted universe multiverse 3.更新软件列表，执行命令 # 更新软件列表，换源成功sudo apt update