Debian is the basis for Ubuntu, but in some ways you can argue that Ubuntu has at this point, exceeded Debian. The great ‘failure’ of Debian is also it’s great strength. Debian hasn’t been able to put out releases in a regularly scheduled format in years — something developers will commonly attribute to not making a release until it’s ready.
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One thing is for sure, Ubuntu continues to be built on the shoulders of Debian. Depending on how you look at it that’s a good thing for Debian (or bad) and it’s definitely a good thing for Ubuntu.