安装ROS执行以下指令时报错

sudo rosdep init

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.

原因

这是由于 raw.githubusercontent.com 被墙，程序无法下载相应的文件导致的。所以要确保 raw.githubusercontent.com 能够被正常访问。这个网站被墙的方式是dns污染，所以我们只要能够找到这个网站的正确 IP 就可以了

解决办法

1.查询IP地址

给大家几个查询 raw.githubusercontent.com 的 IP 地址比较稳定的网站：
网站1
网站2
网站3
将 raw.githubusercontent.com 粘贴到 IP 地址查询框内，得到类似下图的结果

ROS平台安装时，初始化rosdep报错，在进行

rosdep update
出现超时报错

reading in sources list data from /etc/ros/rosdep/sources.list.d
ERROR: error loading sources list:
	The read operation timed out

按照该文方法执行rosdep update,仍然出现超时错误，进而想到直接在sources.list.d中直接添加https://ghproxy.com/前缀，具体操作如下：

连接手机热点，打开终端执行

sudo vim /etc/ros/rosdep/sources.list.d/20-default.list

修改list内容

# os-specific listings first
yaml https://ghproxy.com/https://raw.githubusercontent.com/ros/rosdistro/master/rosdep/osx-homebrew.yaml osx
 
# generic
yaml https://ghproxy.com/https://raw.githubusercontent.com/ros/rosdistro/master/rosdep/base.yaml
yaml https://ghproxy.com/https://raw.githubusercontent.com/ros/rosdistro/master/rosdep/python.yaml
yaml https://ghproxy.com/https://raw.githubusercontent.com/ros/rosdistro/master/rosdep/ruby.yaml
gbpdistro https://ghproxy.com/https://raw.githubusercontent.com/ros/rosdistro/master/releases/fuerte.yaml fuerte
 
# newer distributions (Groovy, Hydro, ...) must not be listed anymore, they are being fetched from the rosd

/etc/ros/rosdep/sources.list.d/20-default.list

185.199.108.133 raw.githubusercontent.com

echo "185.199.108.133 raw.githubusercontent.com" >> /etc/hosts