ROS noetic installation failed at sudo apt-get update

edit

Hello,

I followed the installation process for ROS Noetic on Ubuntu.

1) I set up ROS Noetic repo:

echo "deb http://packages.ros.org/ros/ubuntu focal main" | sudo tee /etc/apt/sources.list.d/ros-focal.list

2) Add official ROS keyring:

sudo apt-key adv --keyserver 'hkp://keyserver.ubuntu.com:80' --recv-key C1...

3) Update ROS package index

sudo apt update

OUTPUT:

sudo apt-get update

Err:1 http://package.ros.org/ros/ubuntu focal InRelease Could not resolve 'package.ros.org' Hit:2 http://ports.ubuntu.com/ubuntu-ports groovy InRelease Hit:3 http://ports.ubuntu.com/ubuntu-ports groovy-updates InRelease Hit:4 http://ports.ubuntu.com/ubuntu-ports groovy-backports InRelease Hit:5 http://ports.ubuntu.com/ubuntu-ports groovy-security InRelease Reading package lists... Done W: Failed to fetch http://package.ros.org/ros/ubuntu/dists/focal/InRelease Could not resolve 'package.ros.org' W: Some index files failed to download. They have been ignored, or old ones used instead.