Failed to initialize rosdep after installing ROS

installed ROS after , initial sudo rosdep init, Show ：
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.
resolvent ：

First /etc Open the terminal in the directory , Enter the following command to change hosts File permissions

sudo chmod a+rw hosts

Then open hosts file , Add the following at the end of the file , And save and exit

151.101.84.133  raw.githubusercontent.com

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If hosts Added IP If the address doesn't solve your problem , It is recommended to use This Check the most suitable IP, Then change it