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：

备份 /etc/apt/sources.list 文件
执行命令

sudo cp /etc/apt/sources.list /etc/apt/sources.list.old

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 multiversedeb-src http://mirrors.aliyun.com/ubuntu/ bionic main restricted universe multiversedeb http://mirrors.aliyun.com/ubuntu/ bionic-security main restricted universe multiversedeb-src http://mirrors.aliyun.com/ubuntu/ bionic-security main restricted universe multiversedeb http://mirrors.aliyun.com/ubuntu/ bionic-updates main restricted universe multiversedeb-src http://mirrors.aliyun.com/ubuntu/ bionic-updates main restricted universe multiversedeb http://mirrors.aliyun.com/ubuntu/ bionic-proposed main restricted universe multiversedeb-src http://mirrors.aliyun.com/ubuntu/ bionic-proposed main restricted universe multiversedeb http://mirrors.aliyun.com/ubuntu/ bionic-backports main restricted universe multiversedeb-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 multiversedeb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic-updates main restricted universe multiversedeb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic-backports main restricted universe multiversedeb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic-security main restricted universe multiversedeb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ trusty main universe restricted multiversedeb http://arcHive.ubuntu.com/ubuntu/ trusty main universe restricted multiverse

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.list2.sudo apt update然后安装ros-melodic-xxx类的软件包就好使了。

来源地址：https://blog.csdn.net/m0_45805756/article/details/126310136