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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 denotes
the "root" of the filesystem; other directories such as the Nix store
directory (as denoted by the store setting) are interpreted relative
to root. 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 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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