First, make sure the Universe, Multiverse and (if you want) Partners repositories are enabled…
Go to System>Administration>Synaptic Package Manager (or wherever they hide the Synaptic Package Manager in the netbook edition)
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To open Synaptic in Unity…
Click the Application lens icon on the “Launcher” sidebar (magnifying glass with + sign in it)… enter synaptic in the search box… click on the Synaptic Package Manager icon
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When Synaptic opens, go to Settings>Repositories>Ubuntu Software (tab)
Put ticks in:
Community maintained Open Source software (universe)
and
Software restricted by copyright or legal issues (multiverse)
and while you’re at it
Proprietary Drivers for devices (restricted)
Also whist you’re here, you might want to enable the “Partners” repositories
(which will give you access to extra software in the future, stuff like skype, and sun java, etc.)
If so, click the “Other Software” (tab), and put ticks in:
Canonical Partners
and (if you want)
Canonical Partners (Source Code)
Click Close
Now click the “Reload” button on the toolbar.
Now you need to install the “ubuntu-restricted-extras” package.
Still in Synaptic, type: ubuntu-restricted-extras into the "Quicksearch"box.
Look for it in the “Package” column in the main right-hand panel.
Click the little box to the left of ubuntu-restricted-extras and select “Mark for Installation”… click “Mark” on the next window that opens.
On the main Synaptic toolbar, click the “Apply” button.
That will download and install the flashplayer plugin and some other useful stuff like support for mp3’s etc.
Close Synaptic (you MUST close Synaptic or the next commands won’t work).
Now to enable playing of commercial DVD’s… open a terminal and enter:
sudo apt-get install libdvdread4
then
sudo /usr/share/doc/libdvdread4/install-css.sh
Hitting enter after each command, and your password when asked.