I know that one of the strengths of NixOS is to allow running different versions of the same package. However, I cannot figure out how to do it for system packages.
For example, say that I have installed Julia 1.6 via:
environment.systemPackages = with pkgs; [ julia_16-bin ];
Now, Julia is available by running
rik@nixos ~> julia -e 'println(VERSION)' 1.6.1
Can I now also get, for example, Julia 1.5, which is available as
julia-stable and load that via something like:
rik@nixos ~> julia_stable -e 'println(VERSION)' 1.5.3
Would that mean adding a new derivation via
stdenv.mkDerivation, or can I just override the command somewhere?