community.linuxmint.com

Check the APT sources:

• /etc/apt/sources.list
• any additional sources in /etc/apt/sources.list.d/

You should see the following:

• Linux Mint repository
• Linux Mint edition repository (unless it's a Gnome edition)
• 3 Ubuntu repositories (main repo, update and security)
• Canonical partners repository
• Medibuntu
• No source repos
• The following components for Linux Mint: main upstream import
• The following components for Ubuntu: main restricted universe multiverse

If repositories are deemed important by the maintainer, they can be added but they need to be commented out and their key needs to be added to the system (check with "sudo apt-key list").

Here's an example of a sources.list file:

deb http://packages.linuxmint.com/ julia main upstream import

deb http://packages.linuxmint.com/ julia-kde main upstream import
deb http://archive.ubuntu.com/ubuntu/ maverick main restricted universe multiverse
deb http://archive.ubuntu.com/ubuntu/ maverick-updates main restricted universe multiverse
deb http://security.ubuntu.com/ubuntu/ maverick-security main restricted universe multiverse
deb http://archive.canonical.com/ubuntu/ maverick partner
deb http://packages.medibuntu.org/ maverick free non-free

#deb http://archive.getdeb.net/ubuntu maverick-getdeb apps
#deb http://archive.getdeb.net/ubuntu maverick-getdeb games
 

Non-gnome editions should contain references to their own repositories, as well as common Linux Mint repositories.

Romeo should not be enabled.

Source repos should not be enabled.