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Store URL format: local, root
This store type accesses a Nix store in the local filesystem directly
(i.e. not via the Nix daemon). root is an absolute path that is
prefixed to other directories such as the Nix store directory. The
store pseudo-URL local denotes a store that uses / as its root
directory.
A store that uses a root other than / is called a chroot
store. With such stores, the store directory is "logically" still
/nix/store, so programs stored in them can only be built and
executed by chroot-ing into root. Chroot stores only support
building and running on Linux when mount namespaces and user namespaces are
enabled.
For example, the following uses /tmp/root as the chroot environment
to build or download nixpkgs#hello and then execute it:
# nix run --store /tmp/root nixpkgs#hello
Hello, world!
Here, the "physical" store location is /tmp/root/nix/store, and
Nix's store metadata is in /tmp/root/nix/var/nix/db.
It is also possible, but not recommended, to change the "logical"
location of the Nix store from its default of /nix/store. This makes
it impossible to use default substituters such as
https://cache.nixos.org/, and thus you may have to build everything
locally. Here is an example:
# nix build --store 'local?store=/tmp/my-nix/store&state=/tmp/my-nix/state&log=/tmp/my-nix/log' nixpkgs#hello
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