(Author here) Docker basically packages together a bunch of technologies into something very usable and, at this point, pretty standard. So I could do some of

(Author here) Docker basically packages together a bunch of technologies into something very usable and, at this point, pretty standard. So I could do some of this stuff using chroots, namespaces, and manually fixing up filesystems... but then I'll just reimplement a worse, less standard Docker. For example, I use cache mounts to get improved performance across executions. Writing that manually is going to involve mantaining a database and cache eviction policies and whatnot. Docker's actually quite lightweight for that same sort of reason. It's basically just "coordinator for a bunch of stuff already built into Linux". If I had to manually implement the sandbox it would be a massive amount of work for no real gain imo. > Plus, inevitably makes it more difficult to work in Windows or Mac. It's way easier to use Docker for Windows/ OSX than it is for me to build a custom sandbox/ CoW system for them, and things will get better on those operating systems for Docker without me having to do work.