The nix manual states that

A Nix archive can be unpacked using nix-store --restore.

However, this does not seem to be the case. I started with the following file:

with import <nixpkgs> {};

stdenv.mkDerivation {
  name = "test1";
  buildCommand = "echo hello > $out";
}

I built this with nix and created a dump file:

$ nix-build test.nix
these derivations will be built:
  /nix/store/giiccnygmwnls3zhs7pibx89xfl0arya-test1.drv
building path(s) ‘/nix/store/ma6agnfk5103hfrr4v4hgd46rasn0hxc-test1’
/nix/store/ma6agnfk5103hfrr4v4hgd46rasn0hxc-test1
$ nix-store --dump /nix/store/ma6agnfk5103hfrr4v4hgd46rasn0hxc-test1 > dump

I then copied this dump file to a virtual machine with a fresh installation of nix (running on CentOS 7). When I attempt to restore it, the command succeeds and the store object is created:

$ cat dump | nix-store --restore /nix/store/ma6agnfk5103hfrr4v4hgd46rasn0hxc-test1
$ ls /nix/store | grep 'test1$'
ma6agnfk5103hfrr4v4hgd46rasn0hxc-test1

However, the created store object does not appear in the SQLite database, and nix-store does not seem to be able to do anything with the file:

$ sqlite3 /nix/var/nix/db/db.sqlite
sqlite> select * from ValidPaths where path = '/nix/store/ma6agnfk5103hfrr4v4hgd46rasn0hxc-test1';
(nothing)
$ nix-store -q /nix/store/ma6agnfk5103hfrr4v4hgd46rasn0hxc-test1
error: path ‘/nix/store/wvnxq72s8jabgl9jv0whdff2ijsxp90b-test1’ does not exist and cannot be created

Apparently it is not sufficient to simply perform a nix-store --restore on the result of a nix-store --dump. I assume that there are subsequent steps required to load the restored object and its metadata into the nix database. This is probably just a documentation issue, because nix-copy-closure is able to copy objects without trouble. However, it's not really clear how to do manual object transfer using dump/restore, without doing the database part manually (which certainly isn't desirable).

Also, when I attempt to do a --restore on nixos, I get Read-only file system errors.