查找自己版本对应的软件源
https://mirrors.tuna.tsinghua.edu.cn/help/ubuntu/
以下为19.10版本的
# 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/ eoan main restricted universe multiverse # deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ eoan main restricted universe multiverse deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ eoan-updates main restricted universe multiverse # deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ eoan-updates main restricted universe multiverse deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ eoan-backports main restricted universe multiverse # deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ eoan-backports main restricted universe multiverse deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ eoan-security main restricted universe multiverse # deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ eoan-security main restricted universe multiverse # 预发布软件源，不建议启用 # deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ eoan-proposed main restricted universe multiverse # deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ eoan-proposed main restricted universe multiverse
修改/etc/apt/source.list文件为以上软件源，然后进行更新
sudo apt-get update
其他常用命令
sudo apt-get update 更新源 sudo apt-get install package 安装包 sudo apt-get remove package 删除包 sudo apt-cache search package 搜索软件包 sudo apt-cache show package 获取包的相关信息，如说明、大小、版本等 sudo apt-get install package --reinstall 重新安装包 sudo apt-get -f install 修复安装 sudo apt-get remove package --purge 删除包，包括配置文件等 sudo apt-get build-dep package 安装相关的编译环境 sudo apt-get upgrade 更新已安装的包 sudo apt-get dist-upgrade 升级系统 sudo apt-cache depends package 了解使用该包依赖那些包 sudo apt-cache rdepends package 查看该包被哪些包依赖 sudo apt-get source package 下载该包的源代码 sudo apt-get clean && sudo apt-get autoclean 清理无用的包 sudo apt-get check 检查是否有损坏的依赖