Ubuntu
By default, Ubuntu does not enable the Universe and Multiverse repositories. There may also be non-Ubuntu sources that you might wish to add to your Ubuntu machine, though this is generally not recommended.
Adding Universe and Multiverse
Synaptic Package manager in sightly different places between Warty and Hoary/Breezy.
Hoary Hedgehog and Breezy Badger
Start Synaptic Package Manager from the System , Administration menu.
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Warty Warthog
Start Synaptic Package Manager from the Computer , System Configuration menu
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On all Ubuntu versions
In Synaptic, choose the Repositories item in the Settings menu
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A list of repositories is shown. Click the Settings button at the bottom and tick Show disabled software sources. Then click the Close button.
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You should now see checkboxes next to the repositories. Scroll down and enable the Universe repository by ticking the checkbox next to Community Maintained (Universe). Click OK to save your settings. You may also want to enable Multiverse and the Universe Security updates repositories.
attachment:enableuniverse.jpg
Save the changes and close the window by clicking OK.
Update the list of available packages with Reload in the main window.
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Once the package list has been updated, packages from universe can be installed.
Adding outside repositories
Sometimes other users will make repositories for packages they have made. It is real easy to add these repositories to the system package manager.
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Note: BE CAREFUL doing this, some outside packages could break your Ubuntu installation.
For a list of outside repositories see BreakMyUbuntu.
Adding outside repositories using Synaptic
As shown in the Using Synaptic screenshot above, start Synaptic Package Manager from the Computer menu, System Configuration item. Once Synaptic has launched, choose the Settings menu, [Repositories] item.
You now see a window with a list of repositories. Push the button New to add a repository. Type in the information about the repositories in the dropdown menu and three textfields according to the following examples.
Normally you find websites providing information about a repository in a form like the following example:
deb http://www.grawert.net/ubuntu/ warty universe
This line provides the information for the Synaptic fields.
* deb means it is a binary, so use the drop-down list to choose binary. Normally this is the default setting.
* http://www.grawert.net/ubuntu/ is the URI (Uniform Resource Identifier), which means in this case the location.
* warty is the release name.
* universe is the section name.
Sometimes the repository line has less information though, as shown in the next example.
deb http://www.getsweaaa.com/~tseng/ubuntu/debs ./
The first two fields (deb and URI) are clearly similar to the first example above. However, the release-name is "./" so just put this (without the quotes) in the release field of Synaptic. It looks weird, but simply specifies the release as being whatever is in the directory given by the URI. Furthermore, there is no section information so just leave that text field blnk in your Synaptic entry.
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Note: Only the section information is optional, and then only with respect to the repository-maintainer. If there is section information, it must be specifed in Synaptic. It cannot be left blank.
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Note: If you make a mistake with the syntax in the fields you will get an error when you click the OK button in Synaptic. One cause is putting a trailing slash at the end of the URI. Also beware of leaving whitespaces at the beginning/end of the fields.
Save the changes and close the window by pushing on OK.
Update the list of avaible packages with Reload in the main window. After downloading the packages list from the repositories you can install packages from universe.
Hoary Extras
Hoary extras contains software that Ubuntu cannot legally ship. Some of this software may be illegal where you live. Use at your own risk.
To add hoary-extras, add the following:
deb http://ubuntu-backports.mirrormax.net/ hoary-extras main universe multiverse restricted