# 使用http源规避证书问题cat /etc/apt/sources.list EOFdeb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal main restricted universe multiversedeb-src http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal main restricted universe multiversedeb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal-updates main restricted universe multiverse deb-src http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal-updates main restricted universe multiversedeb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal-security main restricted universe multiverse deb-src http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal-security main restricted universe multiverse EOF