YouTube lets you download content offline on your phone, provided you’re using the official YouTube app. This feature doesn’t exist on the desktop. If you’re a Linux user with a spotty internet connection, you don’t get the greatest experience when you watch a video on YouTube. Thankfully, there are tools out there that let you save YouTube videos on Linux so you can watch them later. In this article, we’ll be going over the most popular (and arguably the most useful) YouTube video tool; YouTube-DL. It lets you save YouTube videos on Linux and directly from YouTube in multiple formats, and even convert them to an MP3 audio file too.
See http://www.addictivetips.com/ubuntu-linux-tips/save-youtube-videos-on-linux/ 
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