doc: clarify building-nixos CD/DVD instructions

This change updates the instructions for building a NixOS ISO so that it's clear how to do it.

Previously, the instructions stated to set NIXOS_CONFIG prior to running `nix-build`, yet the example provided by-passed NIXOS_CONFIG anyway. But the *really* important missing piece is the need for nixos/default.nix. See #21840.

This change removes the NIXOS_CONFIG verbiage, and adds steps to clone nixpkgs and (most importantly) cd'ing into nixpkgs/nixos. That way, the reader may think: *Oh, so I need a default.nix and a configuration.nix. Ahhh, OK.*

I purposely added the redundant default.nix argument.
This commit is contained in:
Emmanuel Rosa 2017-06-02 20:58:41 -04:00 committed by Graham Christensen
parent 4576e8dddd
commit 4bee34dcc5
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@ -12,12 +12,12 @@ your <filename>configuration.nix</filename> to configure the system that
would be installed on the CD.</para>
<para>Default CD/DVD configurations are available
inside <filename>nixos/modules/installer/cd-dvd</filename>. To build them
you have to set <envar>NIXOS_CONFIG</envar> before
running <command>nix-build</command> to build the ISO.
inside <filename>nixos/modules/installer/cd-dvd</filename>.
<screen>
$ nix-build -A config.system.build.isoImage -I nixos-config=modules/installer/cd-dvd/installation-cd-minimal.nix</screen>
$ git clone https://github.com/NixOS/nixpkgs.git
$ cd nixpkgs/nixos
$ nix-build -A config.system.build.isoImage -I nixos-config=modules/installer/cd-dvd/installation-cd-minimal.nix default.nix</screen>
</para>