So, you can copy both to and from nixbuild.net but you have to select the right combination of commands and protocols. We should fix this so all combinations work.
Most of the closure copying scenarios have now been fixed, but this is still not working: nix copy --from ssh://eu.nixbuild.net. This issue will be kept open until that use case has been fixed.
The following works:
nix-copy-closure --to eu.nixbuild.net
nix copy --to ssh-ng://eu.nixbuild.net
nix copy --from ssh-ng://eu.nixbuild.net
The following does not work:
nix-copy-closure --from eu.nixbuild.net
nix copy --from ssh://eu.nixbuild.net
So, you can copy both to and from nixbuild.net but you have to select the right combination of commands and protocols. We should fix this so all combinations work.