It would be nice to have some switches to perform an upgrade of only some machines in the model, or to exclude certain machines. E.g.

$ nixos-deploy-network --only cartman

or

$ nixos-deploy-network --exclude lucifer

Submitted by Eelco Dolstra on 2 December 2010 at 18:48

The semantics of this operation are a bit unclear to me. In principle a machine can also refer to another machine, which is used for example in the Apache proxy test case:

{ test1 = {pkgs, config, ...}:
    networking.hostName = "test1.example.org";
    # some options
  ;

  test2 = {pkgs, config, test1, ...}:
    someProperty = "${test1.networking.hostName}"; # Use the hostname property of machine test1
    # some options
  ;
}

There are some cases in which both test2 and test1 need to be updated, e.g. if the hostname of machine test1 changes. A partial upgrade of machine test2 may break things.