After you do the below you can install the downloader:
The Download Program Itself (sudo apt-get install youtube-dl)
Refer: http://www.techdrivein.com/2013/08/best-youtube-videos-downloading-tool-for-ubuntu-youtube-dl.html
Usage:
youtube-dl -f mp4 https://www.youtube.com/watch?v=pdz5kCaCRFM
Ideas for Download Solutions:
Refer: http://www.techdrivein.com/2013/08/best-youtube-videos-downloading-tool-for-ubuntu-youtube-dl.html
How to Upgrade to Get Latest Version:
Refer: http://askubuntu.com/questions/429746/youtube-dl-stopped-working
Youtube updates his anti-download security system quite offen. You should keep your youtube-dl up-to-date. The version Ubuntu 12.04 Precis installs by default is 2012.02.27 (two years old).
You can subscribe to the WebUpd8 PPA to get new releases when they're out (that is once or twice a week) :
$ sudo add-apt-repository ppa:nilarimogard/webupd8 -y
$ sudo apt-get update
$ sudo apt-get dist-upgrade
You'll also find the .deb package of the latest youtube-dl release on that PPA (here and search for youtube-dl). Install it with a GUI-tool like gdebi or Ubuntu Software Center, or with these command lines :
$ cd directory/where/you/downloaded/the/package
$ dpkg -i youtube-dl*
$ sudo apt-get install -f