ubuntu换源

# 删掉/etc/apt/sources.list源文件
sudo rm -rf /etc/apt/sources.list

# 删掉/etc/apt/sources.list.d源文件夹
sudo rm -rf /etc/apt/sources.list.d

# 新建/etc/apt/sources.list.d源目录
sudo mkdir -p /etc/apt/sources.list.d

# 写入中科大的源
sudo tee /etc/apt/sources.list > /dev/null << 'EOF'
deb http://mirrors.ustc.edu.cn/ubuntu/ focal main restricted universe multiverse
deb http://mirrors.ustc.edu.cn/ubuntu/ focal-updates main restricted universe multiverse
deb http://mirrors.ustc.edu.cn/ubuntu/ focal-backports main restricted universe multiverse
deb http://mirrors.ustc.edu.cn/ubuntu/ focal-security main restricted universe multiverse
EOF

# 更新包列表索引
sudo apt update