问题描述：

Ubuntu下连接raw.githubusercontent.com失败

1. wget https://raw.githubusercontent.com/madmashup/targeted-marketing-predictive-engine/master/banking.csv

2.  

3. --2020-05-17 17:00:19-- https://raw.githubusercontent.com/madmashup/targeted-marketing-predictive-engine/master/banking.csv

4. Resolving raw.githubusercontent.com (raw.githubusercontent.com)... 0.0.0.0, ::

5. Connecting to raw.githubusercontent.com (raw.githubusercontent.com)|0.0.0.0|:443... failed: Connection refused.

6. Connecting to raw.githubusercontent.com (raw.githubusercontent.com)|::|:443... failed: Network is unreachable.

解决方法：

step-1

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

输入raw.githubusercontent.com查询IP地址

step-2

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

step-3 重启网络

sudo /etc/init.d/networking restart

发现仍然有问题：

ping raw.githubusercontent.com
PING raw.githubusercontent.com (127.0.0.1) 56(84) bytes of data.
64 bytes from localhost (127.0.0.1): icmp_seq=1 ttl=64 time=0.015 ms

查看sudo vi /etc/resolv.conf，发现只有

nameserver 127.0.0.1

加上谷歌DNS服务器

nameserver 8.8.8.8
nameserver 8.8.4.4

问题解决

ping raw.githubusercontent.com
PING github.map.fastly.net (151.101.0.133) 56(84) bytes of data.
64 bytes from 151.101.0.133: icmp_seq=1 ttl=51 time=276 ms

继续安装ros环境

http://wiki.ros.org/cn/kinetic/Installation/Ubuntu

1.5初始化 rosdep

sudo -E rosdep init
rosdep update