We upgraded a whole fleet of AWS / Digitalocean instances without floating IPs from Ubuntu Precise to Xenial based on this method back in the summer of 2017. While obviously not having to do crazy stuff like this would be better, it's nice to know that it is possible if you really need it.
Recently we ran into another use-case for this in production actually, we needed to wipe a lot of servers in our datacenter remotely and we figured one of the options would be to install some OS in memory with the relevant wiping tools, pivot_root to that, unmount all disks and then perform the wipe. In the end we went a different route and opted for a custom PXE-boot image instead that the servers would boot into that scripted the whole thing.
https://www.reddit.com/r/programming/comments/6o7i8p/dont_ru...
Recently we ran into another use-case for this in production actually, we needed to wipe a lot of servers in our datacenter remotely and we figured one of the options would be to install some OS in memory with the relevant wiping tools, pivot_root to that, unmount all disks and then perform the wipe. In the end we went a different route and opted for a custom PXE-boot image instead that the servers would boot into that scripted the whole thing.