解决安装软件包时出现E:无法定位的问题 第一种情况：在确定网络连接和质量没问题的情况下，任何软件都无法安装，出现E:无法定位XXX 解决：换源 具体步骤： 1、备份 /etc/apt/sources.list 文件 执行命令 sudo cp /etc/apt/sources.list /etc/apt/sources.list.old 2、打开文件 sudo vim /etc/apt/sources.list   （gedit也可以） 将原文件里面的内容删掉或注释掉 粘贴选择的源： 阿里云源： deb http://mirrors.aliyun.com/ubuntu/ bionic main restricted universe multiverse deb-src http://mirrors.aliyun.com/ubuntu/ bionic main restricted universe multiverse deb http://mirrors.aliyun.com/ubuntu/ bionic-security main restricted universe multiverse deb-src http://mirrors.aliyun.com/ubuntu/ bionic-security main restricted universe multiverse deb http://mirrors.aliyun.com/ubuntu/ bionic-updates main restricted universe multiverse deb-src http://mirrors.aliyun.com/ubuntu/ bionic-updates main restricted universe multiverse deb http://mirrors.aliyun.com/ubuntu/ bionic-proposed main restricted universe multiverse deb-src http://mirrors.aliyun.com/ubuntu/ bionic-proposed main restricted universe multiverse deb http://mirrors.aliyun.com/ubuntu/ bionic-backports main restricted universe multiverse deb-src http://mirrors.aliyun.com/ubuntu/ bionic-backports main restricted universe multiverse 清华源： deb 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 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 https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ trusty main universe restricted multiverse deb http://archive.ubuntu.com/ubuntu/ trusty main universe restricted multiverse 3.sudo apt-get update 第二种情况：可以安装其他的软件，但唯独无法安装ros--xxx(个人版本是melodic)类的软件包，换源也不好使，可以尝试以下方法（前提：key和ros源完备的情况下）（本人此类情况） 1.echo "deb http://packages.ros.org/ros/ubuntu $(lsb_release -sc) main" | sudo tee /etc/apt/sources.list.d/ros-latest.list 2.sudo apt update 然后安装ros-melodic-xxx类的软件包就好使了。