anchor.diff:                      --shell "$shell"
               fi
   
  +            if test "$group" = nixbld; then
  +                # As a special hack, add users that have nixbld as the
  +                # primary group to the /etc/group entry for the nixbld
  +                # group.  `nix-store' currently expects this in order
  +                # to get the UIDs of all the build users by doing a
  +                # getprnam("nixbld") call.
  +                groupmod "$group" -A "$name"
  +            fi
  +
           done
         '' [ "groups" ];
   
       system.activationScripts.groups = fullDepEntry
         ''
  +        echo "updating groups..."
  +        
           while true; do
               read name || break
               read gid
   
               if ! curEnt=$(getent group "$name"); then
  -                echo "creating group $name..."
                   groupadd --system \
                       "$name" \
                       ''${gid:+--gid $gid}
  
positive.code:              calls in `libstore/build.cc', don't add any supplementary group
               here.  */
            uid = builtins.add ids.uids.nixbld nr;
            group = "nogroup";
            extraGroups = ["nixbld"];
          };
  
        nixBuildUsers = map makeNixBuildUser (pkgs.lib.range 1 10);
  
negative.code: 
      system.activationScripts.users = fullDepEntry
        ''
          echo "updating users..."
  
          cat ${usersFile} | while true; do
              read name || break
              read description
  