The video was posted on YouTube several years ago, but recently popped up on Reddit and I wanted to share it here. It shows Green Day playing in a backyard in 1991 at a graduation party. From the video description:
So this is a cool little clip. Some of my friends managed to get Green Day to play at my graduation party in 1991. Unfortunately one of the opening bands broke the P.A. so we had to try to find a replacement quickly. While we were waiting for the new P.A., Green Day performed this stripped down version of Knowledge to pass the time. By the time the new P.A. showed up it was dark and late and the cops shut it down after only a couple songs. Still an awesome, unforgettable night. Enjoy.
Here's 10 minutes from the rest of that set, but as the uploader pointed out, the video is very dark.
Thanks to the uploader BayAreaPunkShows, and Reddit user KidOverboard for sharing it there.