Installation and usage:
sudo apt-get install youtube-dl
youtube-dl video_url (where video_url is the location on YouTube where said video is hosted).
The video will be saved in the location where we run the command.
If it doesn't work, install:
sudo pip install --upgrade youtube_dl
To update youtube-dl:
youtube-dl -U
(Requires root)
For more information, visit: http://rg3.github.io/youtube-dl/documentation.html