If you're interested in the userspace machinations, as opposed to what goes on in the kernel, there's a great rundown on this StackOverflow answer: https://unix

If you're interested in the userspace machinations, as opposed to what goes on in the kernel, there's a great rundown on this StackOverflow answer: https://unix.stackexchange.com/questions/226872/how-to-shrink-root-filesystem-without-booting-a-livecd/227318#227318 https://unix.stackexchange.com/questions/226872/how-to-shrin... There's also https://github.com/marcan/takeover.sh https://github.com/marcan/takeover.sh (previously on HN: https://news.ycombinator.com/item?id=13622301 https://news.ycombinator.com/item?id=13622301) Both of these share a similar premise - set up and transfer control to an in-memory root filesystem, in order to make major changes to the real root filesystem.