⒈备份官方默认更新源文件
cp /etc/apt/sources.list /etc/apt/sources.list.bak 备份官方更新源文件
⒉编辑
1.打开
vi /etc/apt/sources.list
2.清空内容
ESC后进入命令模式输入
:.,$d
3.复制为以下内容（清华大学镜像站）https://mirrors.tuna.tsinghua.edu.cn/help/ubuntu/
# 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 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 # 预发布软件源，不建议启用 # deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic-proposed main restricted universe multiverse # deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic-proposed main restricted universe multiverse
4.保存
ESC后进入命令模式输入
:wq
⒊更新源
apt update
Ubuntu18.04更换官方默认更新源sources.list
原文：https://www.cnblogs.com/fanqisoft/p/10753092.html