[Nix-dev] Does nix support pre-fetches?

[Peter Simons]

Hi,

there is a wealth of material concerning nix, and I haven't read
everything, so please pardon me if I missed an obvious answer to this
question.

Is it possible to use nix without a permanent connection to the Internet? In
Gentoo Linux, for example, "emerge --sync" updates the package database.
Then, "emerge --fetchonly xorg-x11 mozilla-firefox ..." downloads all files
that are required to install those packages, including dependencies and
everything. The result of the entire operation resides in /usr/portage. I
can copy that directory tree to another machine and install those packages
on the other machine without requiring network access. Can nix do something
similar?

I need that because I'd like to install nix on a set of machines that have
no Internet connection whatsoever (for security reasons). I can get data
onto those machines (by CD-ROM or whatever), but it's an inconvenient and
lengthy process. Downloading packages and data files from the Internet is an
option, but I'd like to batch it.

Is that possible? And if it is, how difficult would it be to keep those
machines up-to-date using that kind of process?

Best regards,
Peter