安装ROS时sudo rosdep init指令报错：

ERROR: cannot download default sources list from:
https://raw.githubusercontent.com/ros/rosdistro/master/rosdep/sources.list.d/20-default.list
Website may be down.

根本原因是无法解析raw.githubusercontent.com

GitHub的raw.githubusercontent.com无法连接问题

https://site.ip138.com/raw.Githubusercontent.com/

输入raw.githubusercontent.com

查询IP地址

修改hosts Ubuntu，CentOS及macOS直接在终端输入

sudo vi /etc/hosts

添加以下内容保存即可 （IP地址查询后相应修改，可以ping不同IP的延时 选择最佳IP地址）

GitHub Start

52.74.223.119 github.com
192.30.253.119 gist.github.com
54.169.195.247 api.github.com
185.199.111.153 assets-cdn.github.com
151.101.76.133 raw.githubusercontent.com
151.101.108.133 user-images.githubusercontent.com
151.101.76.133 gist.githubusercontent.com
151.101.76.133 cloud.githubusercontent.com
151.101.76.133 camo.githubusercontent.com
151.101.76.133 avatars0.githubusercontent.com
151.101.76.133 avatars1.githubusercontent.com
151.101.76.133 avatars2.githubusercontent.com
151.101.76.133 avatars3.githubusercontent.com
151.101.76.133 avatars4.githubusercontent.com
151.101.76.133 avatars5.githubusercontent.com
151.101.76.133 avatars6.githubusercontent.com
151.101.76.133 avatars7.githubusercontent.com
151.101.76.133 avatars8.githubusercontent.com

GitHub End

解决rosdep update时 GitHub的raw.githubusercontent.com无法连接问题

原文：https://www.cnblogs.com/mengydz/p/12890845.html