Ubuntu
Ubuntu is a complete desktop Linux operating system, freely available with both community and professional support. The Ubuntu community is built on the ideas enshrined in the Ubuntu Manifesto: that software should be available free of charge, that software tools should be usable by people in their local language and despite any disabilities, and that people should have the freedom to customise and alter their software in whatever way they see fit.
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Kubuntu
Kubuntu is a free, user-friendly Linux distribution based on KDE's desktop software and on the Ubuntu operating system. It has a biannual release cycle.