please solution for this problem N: Ignoring file 'ros-' in directory '/etc/apt/sources.list.d/' as it has no filename extension

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It's likely that executing the following command from the installation tutorial failed:

sudo sh -c 'echo "deb http://packages.ros.org/ros/ubuntu $(lsb_release -sc) main" > /etc/apt/sources.list.d/ros-latest.list'

It's supposed to be all on a single line (ie: it's all a single command).

Depending on the width of your browser, it could be that you copied only the first part, ending at ros-.

Provided the rest of the command was actually successful, the following should fix the problem you are having:

sudo mv /etc/apt/sources.list.d/ros- /etc/apt/sources.list.d/ros-latest.list

If this does not complain (ie: print an error), you should be able to run sudo apt update. Make sure you've also imported the key.