To deploy a new machine B from an existing machine A, first install NixOS on B. Then:
a$ vim cfg/dev/b.nix
a$ vim cfg/dev/configs.nix
b$ curl https://github.com/Lucus16.keys > /root/.ssh/authorized_keys
a$ nixos-deploy switch b
b$ rm /root/.ssh/authorized_keys
a$ gpg --export lars > lars.gpg
a$ scp lars.gpg b:
b$ gpg --import < lars.gpg
b$ git clone a:cfg
a$ scp -r cfg/secrets b:cfg
b$ cfg/bin/activate