$ nix-build -A dist /nix/store/9i4w0mzp0r8sjkyc8ndfzyjbzlwqp1sb-dist
The dist derivation creates a directory containing the kernel, the initrd, and the rootfs.
It also contains a file with the kernel boot parameters.
In not-os, it contains the value for sysconfig (a path to toplevel), used in the stage-1 init script to resolve the stage-2 init script.
Here, it is baked into stage-1. Doing so means that normally its closure is increased (by the same dependencies of stage-2, i.e. the whole rootfs). But it is possible to artificially remove a dependency with