anchor.diff:  
       system.activationScripts.users = fullDepEntry
         ''
  +        echo "updating users..."
  +
           cat ${usersFile} | while true; do
               read name || break
               read description
  
positive.code:             read password
  
              if ! curEnt=$(getent passwd "$name"); then
                  echo "creating user $name..."
                  useradd --system \
                      "$name" \
                      --comment "$description" \
  
negative.code:              calls in `libstore/build.cc', don't add any supplementary group
               here.  */
            uid = builtins.add ids.uids.nixbld nr;
            group = "nixbld";
            extraGroups = [];
          };
  
        nixBuildUsers = map makeNixBuildUser (pkgs.lib.range 1 10);
  