alt Hacker News> two builds from the same Dockerfile separated by time can result in rather different container images
This is true, and the same is true of shell scripts, but isn't it true of nix as well? If you update nixpkgs and then install something, you have the same chance of getting a new version of it as you do with the `sudo apt-get install` in the Dockerfile, no? I had once looked into using nix to intentionally install older versions of software and it was not as easy as I had hoped.
You can install a single package from a specific nixpkgs commit and it will pull in whatever dependencies it needs to make that work, with everything as of the time of that commit. You may have duplicated libraries but they can coexist fine, and you'd have that with docker as well (probably even worse unless you are very intentional about building layers).
I imagine people do this somewhat regularly at least to e.g. occasionally pull in a package or two from unstable when they normally run a stable system.